U.S. patent application number 13/009675 was filed with the patent office on 2011-07-07 for method and system for printing aligned nanowires and other electrical devices.
This patent application is currently assigned to NANOSYS, INC.. Invention is credited to Erik Freer, James M. Hamilton, Samuel Martin, J. Wallace Parce.
Application Number | 20110165337 13/009675 |
Document ID | / |
Family ID | 39969798 |
Filed Date | 2011-07-07 |
United States Patent
Application |
20110165337 |
Kind Code |
A1 |
Parce; J. Wallace ; et
al. |
July 7, 2011 |
METHOD AND SYSTEM FOR PRINTING ALIGNED NANOWIRES AND OTHER
ELECTRICAL DEVICES
Abstract
Methods and systems for applying nanowires and electrical
devices to surfaces are described. In a first aspect, at least one
nanowire is provided proximate to an electrode pair. An electric
field is generated by electrodes of the electrode pair to associate
the at least one nanowire with the electrodes. The electrode pair
is aligned with a region of the destination surface. The at least
one nanowire is deposited from the electrode pair to the region. In
another aspect, a plurality of electrical devices is provided
proximate to an electrode pair. An electric field is generated by
electrodes of the electrode pair to associate an electrical device
of the plurality of electrical devices with the electrodes. The
electrode pair is aligned with a region of the destination surface.
The electrical device is deposited from the electrode pair to the
region.
Inventors: |
Parce; J. Wallace; (Palo
Alto, CA) ; Hamilton; James M.; (Sunnyvale, CA)
; Martin; Samuel; (Cupertino, CA) ; Freer;
Erik; (Campbell, CA) |
Assignee: |
NANOSYS, INC.
Palo Alto
CA
|
Family ID: |
39969798 |
Appl. No.: |
13/009675 |
Filed: |
January 19, 2011 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
12114446 |
May 2, 2008 |
7892610 |
|
|
13009675 |
|
|
|
|
60916337 |
May 7, 2007 |
|
|
|
Current U.S.
Class: |
427/466 ;
118/621; 427/475 |
Current CPC
Class: |
B82Y 30/00 20130101;
H01L 21/6835 20130101; H01L 2221/68354 20130101; B82B 3/00
20130101; B82Y 40/00 20130101; H01L 2221/68363 20130101 |
Class at
Publication: |
427/466 ;
118/621; 427/475 |
International
Class: |
B05D 1/04 20060101
B05D001/04; B05B 5/025 20060101 B05B005/025 |
Claims
1. A system for transferring nanowires to a destination surface,
comprising: a body having a transfer surface; an electrode pair on
the transfer surface; a suspension that includes a plurality of
nanowires provided proximate to the electrode pair; a signal
generator coupled to the electrode pair, wherein the signal
generator is configured to enable electrodes of the electrode pair
to generate an electric field to associate at least one nanowire of
the plurality of nanowires with the electrodes; and an alignment
mechanism configured to align the electrode pair with a region of
the destination surface to enable the associated at least one
nanowire to be deposited from the electrode pair to the region.
2. A system for applying nanowires to a destination surface,
comprising: a body having a transfer surface; and an electrode pair
formed on the transfer surface; wherein the electrode pair is
configured to generate an electric field to associate a proximate
at least one nanowire with the electrode pair; and wherein the
electrode pair is configured to be aligned with a region of the
destination surface to enable the associated at least one nanowire
to be deposited from the electrode pair to the region.
3. A method for transferring electrical devices to a destination
surface, comprising: providing at least one electrical device
proximate to an electrode pair; generating an electric field with
electrodes of the electrode pair to associate an electrical device
with the electrodes; aligning the electrode pair with a region of
the destination surface; and depositing the electrical device from
the electrode pair to the region.
4. The method of claim 3, wherein the electrical device is an
integrated circuit die, wherein said depositing comprises:
depositing the integrated circuit die from the electrode pair to
the region.
5. The method of claim 3, wherein the electrical device is one of
an integrated circuit, an electrical component, or an optical
device, wherein said depositing comprises: depositing the one of
the integrated circuit, the electrical component, or the optical
device from the electrode pair to the region.
6. The method of claim 3, wherein said depositing comprises:
ultrasonically vibrating the transfer surface to enable an
attractive electrostatic force to attract the electrical device
toward the destination surface.
7. The method of claim 6, wherein said ultrasonically vibrating the
transfer surface comprises: ultrasonically vibrating both the
transfer surface and destination surface.
8. The method of claim 7, wherein said ultrasonically vibrating the
transfer surface further comprises: ultrasonically vibrating the
transfer surface and destination surface synchronously.
9. A system for transferring electrical devices to a destination
surface, comprising: a body having a transfer surface; an electrode
pair on the transfer surface; a suspension that includes a
plurality of electrical devices provided proximate to the electrode
pair; a signal generator coupled to the electrode pair, wherein the
signal generator is configured to enable electrodes of the
electrode pair to generate an electric field to associate an
electrical device of the plurality of electrical devices with the
electrodes; and an alignment mechanism configured to align the
electrode pair with a region of the destination surface to enable
the associated electrical device to be deposited from the electrode
pair to the region.
10. The system of claim 9, wherein the electrical device is an
integrated circuit die.
11. The system of claim 9, wherein the electrical device is one of
an integrated circuit, an electrical component, or an optical
device.
12. A system for applying electrical devices to a destination
surface, comprising: a body having a transfer surface; and an
electrode pair formed on the transfer surface; wherein the
electrode pair is configured to generate an electric field to
associate a proximate electrical device with the electrode pair;
and wherein the electrode pair is configured to be aligned with a
region of the destination surface to enable the associated
electrical device to be deposited from the electrode pair to the
region.
13. The system of claim 12, wherein the electrical device is an
integrated circuit die.
14. The system of claim 12, wherein the electrical device is one of
an integrated circuit, an electrical component, or an optical
device.
15. A method for transferring nanowires to a destination surface,
comprising: positioning a transfer surface of a print head adjacent
to a destination surface, wherein a nanowire is associated with the
transfer surface; reducing a distance between the transfer surface
and the destination surface; receiving a fluid in at least one
opening in the transfer surface from between the transfer surface
and the destination surface during said reducing; and depositing
the nanowire from the transfer surface to the destination
surface.
16. A system for transferring nanowires to a destination surface,
comprising: a body having a transfer surface; at least one opening
in the transfer surface; and an electrode pair formed on the
transfer surface; wherein the electrode pair is configured to
generate an electric field to associate a nanowire with the
electrode pair; and wherein the at least one opening is configured
to receive a fluid from between the transfer surface and the
destination surface.
17. A method for transferring nanowires to a destination substrate,
comprising: associating nanostructures with transfer surfaces of a
plurality of print heads; performing an inspection of the transfer
surfaces of the plurality of print heads; selecting at least one
print head of the plurality of print heads based on the inspection;
and transferring the nanostructures from the selected at least one
print head to a plurality of regions of a surface of a destination
substrate.
18. A method for transferring nanowires to a destination substrate,
comprising: associating nanostructures with transfer surfaces of a
plurality of print heads; drying the transfer surfaces having
associated nanostructures; performing an inspection of the dried
transfer surfaces having associated nanostructures; and
transferring the nanostructures from the dried transfer surfaces to
a plurality of regions of a surface of the destination
substrate.
19. A system for transferring nanowires to a destination substrate,
comprising: an association station configured to receive a
plurality of print heads, and to associate nanostructures with a
transfer surface of each of the received plurality of print heads;
a printing station configured to receive a destination substrate
and at least one of the plurality of print heads, and to transfer
the nanostructures from the received at least one of the plurality
of print heads to a plurality of regions of a surface of the
destination substrate; and a cleaning station configured to receive
the plurality of print heads from the printing station, and to
clean the received plurality of print heads.
20. A system for applying nanowires to a destination surface,
comprising: a body having a transfer surface; a non-stick coating
formed on the transfer surface; and an electrode pair formed on the
transfer surface; wherein the electrode pair is configured to
generate an electric field to associate a proximate at least one
nanowire with the electrode pair; and wherein the electrode pair is
configured to be aligned with a region of the destination surface
to enable the associated at least one nanowire to be deposited from
the electrode pair to the region.
21. A method for transferring nanowires to a destination substrate,
comprising: associating nanostructures with transfer surfaces of a
plurality of print heads; performing an inspection of the transfer
surfaces of the plurality of print heads; determining an
arrangement of nanostructures associated with a transfer surface of
a print head of the plurality of print heads in need of repair;
repairing the determined arrangement of nanostructures; and
transferring the repaired arrangement of nanostructures from the
transfer surface of the print head to a destination substrate.
Description
[0001] This application is a divisional of allowed U.S. application
Ser. No. 12/114,446, filed on May 2, 2008, which claims the benefit
of U.S. Provisional Application No. 60/916,337, filed on May 7,
2007, both of which are incorporated by reference herein in their
entireties.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to nanostructures, and more
particularly, to the deposition of aligned nanostructures and
electrical devices.
[0004] 2. Background of the Invention
[0005] Nanostructures, such as nanowires, have the potential to
facilitate a whole new generation of electronic devices. A major
impediment to the emergence of this new generation of electronic
devices based on nanostructures is the ability to effectively align
and deposit the nanostructures on various surfaces, such as
substrates. Electric fields enable the alignment of nanowires
suspended in suspension, but current techniques pose stringent
constraints on the scalability to large area substrates. Likewise,
current techniques for depositing electrical devices, such as
integrated circuits, dies, optical components, etc., do not scale
well to large area substrates.
[0006] What are needed are systems and methods for achieving a high
quality deposition of nanostructures and other electrical devices
that are suitable for manufacturing large arrays of
nanostructure-enabled electronic devices.
SUMMARY OF THE INVENTION
[0007] Methods and systems for applying nanowires to surfaces are
described. In an example aspect, nanowires are provided proximate
to an electrode pair. An electric field is generated by electrodes
of the electrode pair to associate the nanowires with the
electrodes. The electrode pair is aligned with a region of the
destination surface. The nanowires are deposited from the electrode
pair to the region.
[0008] The nanowires may be deposited to the region in a variety of
ways. For example, a passive or active force, or combination of
such forces, may be used to move the nanowires from the electrodes
to the destination surface. Example forces include an electric
field (AC and/or DC), a vacuum force, an electrostatic force,
gravity, and/or other forces.
[0009] In a first example, the electrode pair may be formed on a
transfer surface. The transfer surface is configured to have a
first electric charge. The first electric charge applies a
repulsive electrostatic force to the nanowires (e.g., the nanowires
may have the same charge as the first electric charge). The
electric field generated by the electrodes attracts the nanowires
to the transfer surface against the repulsive electrostatic force.
In one instance, the electric field may be biased with an
alternating current (AC) field to attract the nanowires to the
transfer surface. The electric field may be reduced (including
entirely removed) to enable the nanowires to be moved toward the
destination surface by the repulsive electrostatic force of the
first electric charge.
[0010] In another example, the destination surface has a second
electric charge that is opposite the first electric charge. An
attractive electrostatic force of the second electric charge
attracts the nanowires to the destination surface. A distance
between the nanowires and the destination surface may be reduced to
increase this attraction.
[0011] In another example, the transfer surface is vibrated (e.g.,
ultrasonically) to enable the attractive electrostatic force of the
second electric charge to attract the nanowires toward the
destination surface.
[0012] In another example, a vacuum is applied from the destination
surface to the transfer surface to move the nanowires toward the
destination surface. For example, the vacuum may draw a solution in
which the nanowires reside towards the destination surface. The
solution flow draws the nanowires toward the destination
surface.
[0013] In another example, a second electric field associated with
the destination surface is generated to attract the nanowires
toward the destination surface.
[0014] In another aspect of the present invention, a system for
applying nanowires to a destination surface is described. The
system includes a body having a transfer surface, an electrode pair
formed on the transfer surface, a suspension that includes a
plurality of nanowires provided proximate to the electrode pair, a
signal generator, and an alignment mechanism. The signal generator
is coupled to the electrode pair. The signal generator is
configured to supply an electric signal to enable electrodes of the
electrode pair to generate an electric field to associate nanowires
of the plurality of nanowires with the electrodes. The alignment
mechanism is configured to align the electrode pair with a region
of the destination surface to enable the nanowires to be deposited
from the electrode pair to the region.
[0015] In another aspect of the present invention, electrical
devices are transferred to surfaces in a similar manner as
described elsewhere herein for nanowires. In aspects, one or more
electrical devices are provided proximate to an electrode pair on a
transfer surface. The electrode pair is energized, whereby an
electrical device becomes associated with the electrode pair.
Subsequently, the electrical device is deposited from the electrode
pair to a destination surface.
[0016] In another aspect of the present invention, nanostructures,
such as nanowires, are transferred to a destination surface. A
transfer surface of a print head is positioned adjacent to a
destination surface. A nanowire is associated with the transfer
surface. A distance between the transfer surface and the
destination surface is reduced. A fluid is received in one or more
openings in the transfer surface from between the transfer surface
and the destination surface during the reducing of the distance
between the transfer and destination surfaces. Receiving the fluid
in the opening(s) reduces a shear force on the nanowire. The
nanowire is deposited from the transfer surface to the destination
surface.
[0017] In still another aspect of the present invention,
nanostructures, such as nanowires, are transferred to a destination
substrate. A nanowire transfer system includes an association
station, a printing station, and a cleaning station. The
association station is configured to receive a plurality of print
heads, and to associate nanostructures with a transfer surface of
each of the received plurality of print heads. The printing station
is configured to receive a destination substrate and at least one
of the print heads, and to transfer the nanostructures from the
received print head(s) to a plurality of regions of a surface of
the destination substrate. The cleaning station is configured to
receive the plurality of print heads from the printing station, and
to clean the received plurality of print heads.
[0018] In aspects, the printing station may be configured to
perform the transfer of the nanostructures as a "wet" transfer or a
"dry" transfer.
[0019] In a further aspect, the nanowire transfer system may
include an inspection station. The inspection station is configured
to perform an inspection of the transfer surfaces of the plurality
of print heads, and to select at least one print head of the
plurality of print heads based on the inspection. The printing
station may be configured to transfer the nanostructures from the
selected at least one print head.
[0020] In a still further aspect, the nanowire transfer system may
include a repair station. The repair station is configured to
perform an inspection of the nanostructures transferred to the
plurality of regions of the surface of the destination substrate.
If the repair station determines an arrangement of nanostructures
in need of repair, the repair station is configured to repair the
arrangement of nanostructures.
[0021] In a still further aspect, the nanowire transfer system may
include a print head drying station and a repair station. The print
head drying station is configured to dry the nanostructures
associated with the transfer surfaces of the plurality of print
heads. The repair station is configured to perform an inspection of
the dried transfer surfaces. If the repair station determines an
arrangement of nanostructures associated with a transfer surface in
need of repair, the repair station is configured to repair the
determined arrangement of nanostructures. The print head drying
station enables a dry transfer of the nanowires to be performed at
the printing station.
[0022] In a still further aspect, the nanowire transfer system may
include a panel drying station. The panel drying station is
configured to dry the nanostructures transferred to the plurality
of regions of the surface of the destination substrate (e.g., if a
wet transfer of the nanowires is performed by the printing
station)
[0023] Further embodiments, features, and advantages of the
invention, as well as the structure and operation of the various
embodiments of the invention are described in detail below with
reference to accompanying drawings.
BRIEF DESCRIPTION OF THE FIGURES
[0024] The invention is described with reference to the
accompanying drawings. In the drawings, like reference numbers
indicate identical or functionally similar elements. The drawing in
which an element first appears is indicated by the left-most digit
in the corresponding reference number.
[0025] FIG. 1A is a diagram of a single crystal semiconductor
nanowire.
[0026] FIG. 1B is a diagram of a nanowire doped according to a
core-shell (CS) structure.
[0027] FIG. 1C is a diagram of a nanowire doped according to a
core-shell-shell (CSS) structure.
[0028] FIG. 2 shows a block diagram of a nanostructure transfer
system, according to an example embodiment of the present
invention.
[0029] FIG. 3 shows a flowchart providing example steps for
transferring nanostructures, according to example embodiments of
the present invention.
[0030] FIGS. 4-6 show block diagram views of the nanostructure
transfer system of FIG. 2 during different phases of operation,
according to example embodiments of the present invention.
[0031] FIG. 7 shows a nanowire print head, according to an
embodiment of the present invention.
[0032] FIGS. 8 and 9 show portions of example nanowire transfer
systems, according to embodiments of the present invention.
[0033] FIG. 10 shows a block diagram of a nanowire solution flow
system, according to an example embodiment of the present
invention.
[0034] FIGS. 11 and 12 show views of an example print head having
cantilevers, according to an example embodiment of the present
invention.
[0035] FIG. 13 shows an electric field generation system for a
transfer system, according to an example embodiment of the present
invention.
[0036] FIG. 14 shows a transfer system, where an electric field is
generated to associate nanowires with an electrode pair, according
to an example embodiment of the present invention.
[0037] FIG. 15 shows the transfer system of FIG. 14, with an
associated nanowire, according to an example embodiment of the
present invention.
[0038] FIG. 16 shows forces acting upon a nanowire in a transfer
system, according to an example embodiment of the present
invention.
[0039] FIGS. 17 and 18 show plan and side views of the print head
of FIG. 11, with associated nanowires, according to example
embodiment of the present invention.
[0040] FIG. 19 shows an alignment system, according to an example
embodiment of the present invention.
[0041] FIG. 20 shows a print head having been aligned with a
surface region by alignment mechanism, according to an embodiment
of the present invention.
[0042] FIGS. 21 and 22 show the print head in solution of FIG. 9
being aligned with a destination surface, according to an example
embodiment of the present invention.
[0043] FIG. 23 shows an example print head with spacers, according
to an embodiment of the present invention.
[0044] FIGS. 24 and 25 show side views of the print head of FIG. 11
in alignment with a destination surface, according to an example
embodiment of the present invention.
[0045] FIG. 26 shows a nanowire transfer system with a vacuum
source, according to an example embodiment of the present
invention.
[0046] FIG. 27 shows an example plan view of a transfer surface
with vacuum ports, according to an example embodiment of the
present invention.
[0047] FIGS. 28, 29, 31A, 31B, 32, and 33 show example nanowire
transfer systems configured to deposit nanowires, according to
example embodiments of the present invention.
[0048] FIG. 30 shows a plot of potential energy levels for a
transfer surface having an oxide layer and for a destination
surface having a nitride layer, according to an embodiment of the
present invention.
[0049] FIG. 31C shows a plot of the inertial motion of nanowires in
isopropyl alcohol, according to an embodiment of the present
invention.
[0050] FIG. 34 shows a nanowire transfer system that includes a
print head having two electrode pairs, according to an embodiment
of the present invention.
[0051] FIG. 35 shows a flowchart providing example steps for
transferring electrical devices, according to example embodiments
of the present invention.
[0052] FIGS. 36-39 show block diagram views of an electrical device
transfer system during different phases of operation, according to
example embodiments of the present invention.
[0053] FIG. 40 shows a cross-sectional view of a nanostructure
transfer system, according to an example embodiment of the present
invention.
[0054] FIG. 41 shows a view of a transfer surface of the print head
shown in FIG. 40, according to an example embodiment of the present
invention.
[0055] FIG. 42 shows a cross-sectional view of a nanostructure
transfer system, according to an example embodiment of the present
invention.
[0056] FIG. 43 show a view of a transfer surface of the print head
shown in FIG. 42, according to an example embodiment of the present
invention.
[0057] FIG. 44 shows a flowchart for transferring nanostructures to
a destination surface, according to an example embodiment of the
present invention.
[0058] FIG. 45 shows a cross-sectional view of the nanostructure
transfer system of FIG. 42, illustrating a nanowire being deposited
to the destination surface, according to an example embodiment of
the present invention.
[0059] FIG. 46 shows a nanostructure transfer system, according to
an embodiment of the present invention.
[0060] FIG. 47 shows a cross-sectional view of a print head,
according to an example embodiment of the present invention.
[0061] FIG. 48 shows a block diagram of a nanostructure printing
system, according to an example embodiment of the present
invention.
[0062] FIG. 49 shows a flowchart for a print head pipeline portion
of the system of FIG. 48, according to an example embodiment of the
present invention.
[0063] FIG. 50 shows a flowchart for a panel pipeline portion of
the system of FIG. 48, according to an example embodiment of the
present invention.
[0064] FIGS. 51 and 52 show views of an example association
station, according to embodiments of the present invention.
[0065] FIG. 53 shows an example inspection station, according to an
embodiment of the present invention.
[0066] FIGS. 54-56 show views of a printing station during a
nanostructure transfer process, according to an example embodiment
of the present invention.
[0067] FIG. 57 shows an example cleaning station, according to an
embodiment of the present invention
[0068] FIGS. 58 and 59 show views of a panel repair station,
according to example embodiments of the present invention.
[0069] FIG. 60 shows an example panel drying station, according to
an embodiment of the present invention.
[0070] FIG. 61 shows a block diagram of a nanostructure printing
system, according to an example embodiment of the present
invention.
[0071] FIG. 62 shows a flowchart for a print head pipeline portion
of the system of FIG. 61, according to an example embodiment of the
present invention.
[0072] FIG. 63 shows a flowchart for a panel pipeline portion of
the system of FIG. 61, according to an example embodiment of the
present invention.
[0073] FIGS. 64, 66, 68, and 70 show views of a nanostructure
transfer system during a nanostructure transfer process, according
to example embodiments of the present invention.
[0074] FIGS. 65, 67, 69, and 71 show respective images captured
using a microscope of the nanostructure transfer system shown in
FIGS. 64, 66, 68, and 70, according to example embodiments of the
present invention.
[0075] The present invention will now be described with reference
to the accompanying drawings. In the drawings, like reference
numbers indicate identical or functionally similar elements.
Additionally, the left-most digit(s) of a reference number
identifies the drawing in which the reference number first
appears.
DETAILED DESCRIPTION OF THE INVENTION
[0076] It should be appreciated that the particular implementations
shown and described herein are examples of the invention and are
not intended to otherwise limit the scope of the present invention
in any way. Indeed, for the sake of brevity, conventional
electronics, manufacturing, semiconductor devices, and nanowire
(NW), nanorod, nanotube, and nanoribbon technologies and other
functional aspects of the systems (and components of the individual
operating components of the systems) may not be described in detail
herein. Furthermore, for purposes of brevity, the invention is
frequently described herein as pertaining to nanowires.
[0077] It should be appreciated that although nanowires are
frequently referred to, the techniques described herein are also
applicable to other nanostructures, such as nanorods, nanotubes,
nanotetrapods, nanoribbons and/or combinations thereof. It should
further be appreciated that the manufacturing techniques described
herein could be used to create any semiconductor device type, and
other electronic component types. Further, the techniques would be
suitable for application in electrical systems, optical systems,
consumer electronics, industrial electronics, wireless systems,
space applications, or any other application.
[0078] As used herein, an "aspect ratio" is the length of a first
axis of a nanostructure divided by the average of the lengths of
the second and third axes of the nanostructure, where the second
and third axes are the two axes whose lengths are most nearly equal
to each other. For example, the aspect ratio for a perfect rod
would be the length of its long axis divided by the diameter of a
cross-section perpendicular to (normal to) the long axis.
[0079] The term "heterostructure" when used with reference to
nanostructures refers to nanostructures characterized by at least
two different and/or distinguishable material types. Typically, one
region of the nanostructure comprises a first material type, while
a second region of the nanostructure comprises a second material
type. In certain embodiments, the nanostructure comprises a core of
a first material and at least one shell of a second (or third etc.)
material, where the different material types are distributed
radially about the long axis of a nanowire, a long axis of an arm
of a branched nanocrystal, or the center of a nanocrystal, for
example. A shell need not completely cover the adjacent materials
to be considered a shell or for the nanostructure to be considered
a heterostructure. For example, a nanocrystal characterized by a
core of one material covered with small islands of a second
material is a heterostructure. In other embodiments, the different
material types are distributed at different locations within the
nanostructure. For example, material types can be distributed along
the major (long) axis of a nanowire or along a long axis of arm of
a branched nanocrystal. Different regions within a heterostructure
can comprise entirely different materials, or the different regions
can comprise a base material.
[0080] As used herein, a "nanostructure" is a structure having at
least one region or characteristic dimension with a dimension of
less than about 500 nm, e.g., less than about 200 nm, less than
about 100 nm, less than about 50 nm, or even less than about 20 nm.
Typically, the region or characteristic dimension will be along the
smallest axis of the structure. Examples of such structures include
nanowires, nanorods, nanotubes, branched nanocrystals,
nanotetrapods, tripods, bipods, nanocrystals, nanodots, quantum
dots, nanoparticles, branched tetrapods (e.g., inorganic
dendrimers), and the like. Nanostructures can be substantially
homogeneous in material properties, or in certain embodiments can
be heterogeneous (e.g., heterostructures). Nanostructures can be,
for example, substantially crystalline, substantially
monocrystalline, polycrystalline, amorphous, or a combination
thereof. In one aspect, each of the three dimensions of the
nanostructure has a dimension of less than about 500 nm, for
example, less than about 200 nm, less than about 100 nm, less than
about 50 nm, or even less than about 20 nm.
[0081] As used herein, the term "nanowire" generally refers to any
elongated conductive or semiconductive material (or other material
described herein) that includes at least one cross-sectional
dimension that is less than 500 nm, and preferably, equal to or
less than less than about 100 nm, and has an aspect ratio
(length:width) of greater than 10, preferably greater than 50, and
more preferably, greater than 100. Exemplary nanowires for use in
the practice of the methods and systems of the present invention
are on the order of 10's of microns long (e.g., about 10, 20, 30,
40, 50 microns, etc.) and about 100 nm in diameter.
[0082] The nanowires of this invention can be substantially
homogeneous in material properties, or in certain embodiments can
be heterogeneous (e.g., nanowire heterostructures). The nanowires
can be fabricated from essentially any convenient material or
materials, and can be, e.g., substantially crystalline,
substantially monocrystalline, polycrystalline, or amorphous.
Nanowires can have a variable diameter or can have a substantially
uniform diameter, that is, a diameter that shows a variance less
than about 20% (e.g., less than about 10%, less than about 5%, or
less than about 1%) over the region of greatest variability and
over a linear dimension of at least 5 nm (e.g., at least 10 nm, at
least 20 nm, or at least 50 nm). Typically the diameter is
evaluated away from the ends of the nanowire (e.g., over the
central 20%, 40%, 50%, or 80% of the nanowire). A nanowire can be
straight or can be e.g., curved or bent, over the entire length of
its long axis or a portion thereof. In certain embodiments, a
nanowire or a portion thereof can exhibit two- or three-dimensional
quantum confinement. Nanowires according to this invention can
expressly exclude carbon nanotubes, and, in certain embodiments,
exclude "whiskers" or "nanowhiskers", particularly whiskers having
a diameter greater than 100 nm, or greater than about 200 nm.
[0083] Examples of such nanowires include semiconductor nanowires
as described in Published International Patent Application Nos. WO
02/17362, WO 02/48701, and WO 01/03208, carbon nanotubes, and other
elongated conductive or semiconductive structures of like
dimensions, which are incorporated herein by reference.
[0084] As used herein, the term "nanorod" generally refers to any
elongated conductive or semiconductive material (or other material
described herein) similar to a nanowire, but having an aspect ratio
(length:width) less than that of a nanowire. Note that two or more
nanorods can be coupled together along their longitudinal axis so
that the coupled nanorods span all the way between electrodes.
Alternatively, two or more nanorods can be substantially aligned
along their longitudinal axis, but not coupled together, such that
a small gap exists between the ends of the two or more nanorods. In
this case, electrons can flow from one nanorod to another by
hopping from one nanorod to another to traverse the small gap. The
two or more nanorods can be substantially aligned, such that they
form a path by which electrons can travel between electrodes.
[0085] A wide range of types of materials for nanowires, nanorods,
nanotubes and nanoribbons can be used, including semiconductor
material selected from, e.g., Si, Ge, Sn, Se, Te, B, C (including
diamond), P, B--C, B--P(BP.sub.6), B--Si, Si--C, Si--Ge, Si--Sn and
Ge--Sn, SiC, BN, BP, BAs, MN, AlP, AlAs, AlSb, GaN, GaP, GaAs,
GaSb, InN, InP, InAs, InSb, ZnO, ZnS, ZnSe, ZnTe, CdS, CdSe, CdTe,
HgS, HgSe, HgTe, BeS, BeSe, BeTe, MgS, MgSe, GeS, GeSe, GeTe, SnS,
SnSe, SnTe, PbO, PbS, PbSe, PbTe, CuF, CuCl, CuBr, Cul, AgF, AgCl,
AgBr, Agl, BeSiN.sub.2, CaCN.sub.2, ZnGeP.sub.2, CdSnAs.sub.2,
ZnSnSb.sub.2, CuGeP.sub.3, CuSi.sub.2P.sub.3, (Cu, Ag)(Al, Ga, In,
Tl, Fe)(S, Se, Te).sub.2, Si.sub.3N.sub.4, Ge.sub.3N.sub.4,
Al.sub.2O.sub.3, (Al, Ga, In).sub.2 (S, Se, Te).sub.3, Al.sub.2CO,
and an appropriate combination of two or more such
semiconductors.
[0086] The nanowires can also be formed from other materials such
as metals such as gold, nickel, palladium, iradium, cobalt,
chromium, aluminum, titanium, tin and the like, metal alloys,
polymers, conductive polymers, ceramics, and/or combinations
thereof. Other now known or later developed conducting or
semiconductor materials can be employed.
[0087] In certain aspects, the semiconductor may comprise a dopant
from a group consisting of: a p-type dopant from Group III of the
periodic table; an n-type dopant from Group V of the periodic
table; a p-type dopant selected from a group consisting of: B, Al
and In; an n-type dopant selected from a group consisting of: P, As
and Sb; a p-type dopant from Group II of the periodic table; a
p-type dopant selected from a group consisting of: Mg, Zn, Cd and
Hg; a p-type dopant from Group IV of the periodic table; a p-type
dopant selected from a group consisting of: C and Si; or an n-type
dopant selected from a group consisting of: Si, Ge, Sn, S, Se and
Te. Other now known or later developed dopant materials can be
employed.
[0088] Additionally, the nanowires or nanoribbons can include
carbon nanotubes, or nanotubes formed of conductive or
semiconductive organic polymer materials, (e.g., pentacene, and
transition metal oxides).
[0089] Hence, although the term "nanowire" is referred to
throughout the description herein for illustrative purposes, it is
intended that the description herein also encompass the use of
nanotubes (e.g., nanowire-like structures having a hollow tube
formed axially therethrough). Nanotubes can be formed in
combinations/thin films of nanotubes as is described herein for
nanowires, alone or in combination with nanowires, to provide the
properties and advantages described herein.
[0090] It should be understood that the spatial descriptions (e.g.,
"above", "below", "up", "down", "top", "bottom," "vertical,"
"horizontal," etc.) made herein are for purposes of illustration
only, and that devices of the present invention can be spatially
arranged in any orientation or manner.
[0091] FIG. 1A illustrates a single crystal semiconductor nanowire
core (hereafter "nanowire") 100. FIG. 1A shows a nanowire 100 that
is a uniformly doped single crystal nanowire. Such single crystal
nanowires can be doped into either p- or n-type semiconductors in a
fairly controlled way. Doped nanowires such as nanowire 100 exhibit
improved electronic properties. For instance, such nanowires can be
doped to have carrier mobility levels comparable to bulk single
crystal materials.
[0092] FIG. 1B shows a nanowire 110 having a core-shell structure,
with a shell 112 around the nanowire core. Surface scattering can
be reduced by forming an outer layer of the nanowire, such as by
the passivation annealing of nanowires, and/or the use of
core-shell structures with nanowires. An insulating layer, such as
an oxide coating, can be formed on a nanowire as the shell layer.
Furthermore, for example, for silicon nanowires having an oxide
coating, the annealing of the nanowires in hydrogen (H.sub.2) can
greatly reduce surface states. In embodiments, the core-shell
combination is configured to satisfy the following constraints: (1)
the shell energy level should be higher than the core energy level,
so that the conducting carriers are confined in the core; and (2)
the core and shell materials should have good lattice match, with
few surface states and surface charges. Other more complex NW
core-shell structures may also be used to include a core of single
crystal semiconductor, an inner-shell of gate dielectric, and an
outer-shell of conformal gate, such as shown in FIG. 1C. FIG. 1C
shows a nanowire 114 having a core-shell-shell structure, with an
inner shell 112 and outer shell 116 around the nanowire core. This
can be realized by depositing a layer of TaAlN, WN, or highly-doped
amorphous silicon around the Si/SiO.sub.x core-shell structure
(described above) as the outer-gate shell, for example.
[0093] The valence band of the insulating shell can be lower than
the valence band of the core for p-type doped wires, or the
conduction band of the shell can be higher than the core for n-type
doped wires. Generally, the core nanostructure can be made from any
metallic or semiconductor material, and the one or more shell
layers deposited on the core can be made from the same or a
different material. For example, the first core material can
comprise a first semiconductor selected from the group consisting
of: a Group II-VI semiconductor, a Group III-V semiconductor, a
Group IV semiconductor, and an alloy thereof. Similarly, the second
material of the one or more shell layers can comprise an oxide
layer, a second semiconductor, the same as or different from the
first semiconductor, e.g., selected from the group consisting of: a
Group II-VI semiconductor, a Group III-V semiconductor, a Group IV
semiconductor, and an alloy thereof. Example semiconductors
include, but are not limited to, CdSe, CdTe, InP, InAs, CdS, ZnS,
ZnSe, ZnTe, HgTe, GaN, GaP, GaAs, GaSb, InSb, Si, Ge, AlAs, AlSb,
PbSe, PbS, and PbTe. As noted above, metallic materials such as
gold, chromium, tin, nickel, aluminum etc. and alloys thereof can
be used as the core material, and the metallic core can be
overcoated with an appropriate shell material such as silicon
dioxide or other insulating materials, which may in turn may be
coated with one or more additional shell layers of the materials
described above to form more complex core-shell-shell nanowire
structures.
[0094] Nanostructures can be fabricated and their size can be
controlled by any of a number of convenient methods that can be
adapted to different materials. For example, synthesis of
nanocrystals of various composition is described in, e.g., Peng et
al. (2000) "Shape Control of CdSe Nanocrystals" Nature 404, 59-61;
Puntes et al. (2001) "Colloidal nanocrystal shape and size control:
The case of cobalt" Science 291, 2115-2117; U.S. Pat. No. 6,306,736
to Alivisatos et al. (Oct. 23, 2001) entitled "Process for forming
shaped group III-V semiconductor nanocrystals, and product formed
using process"; U.S. Pat. No. 6,225,198 to Alivisatos et al. (May
1, 2001) entitled "Process for forming shaped group II-VI
semiconductor nanocrystals, and product formed using process"; U.S.
Pat. No. 5,505,928 to Alivisatos et al. (Apr. 9, 1996) entitled
"Preparation of III-V semiconductor nanocrystals"; U.S. Pat. No.
5,751,018 to Alivisatos et al. (May 12, 1998) entitled
"Semiconductor nanocrystals covalently bound to solid inorganic
surfaces using self-assembled monolayers"; U.S. Pat. No. 6,048,616
to Gallagher et al. (Apr. 11, 2000) entitled "Encapsulated quantum
sized doped semiconductor particles and method of manufacturing
same"; and U.S. Pat. No. 5,990,479 to Weiss et al. (Nov. 23, 1999)
entitled "Organo luminescent semiconductor nanocrystal probes for
biological applications and process for making and using such
probes."
[0095] Growth of nanowires having various aspect ratios, including
nanowires with controlled diameters, is described in, e.g.,
Gudiksen et al (2000) "Diameter-selective synthesis of
semiconductor nanowires" J. Am. Chem. Soc. 122, 8801-8802; Cui et
al. (2001) "Diameter-controlled synthesis of single-crystal silicon
nanowires" Appl. Phys. Lett. 78, 2214-2216; Gudiksen et al. (2001)
"Synthetic control of the diameter and length of single crystal
semiconductor nanowires" J. Phys. Chem. B 105, 4062-4064; Morales
et al. (1998) "A laser ablation method for the synthesis of
crystalline semiconductor nanowires" Science 279, 208-211; Duan et
al. (2000) "General synthesis of compound semiconductor nanowires"
Adv. Mater. 12, 298-302; Cui et al. (2000) "Doping and electrical
transport in silicon nanowires" J. Phys. Chem. B 104, 5213-5216;
Peng et al. (2000) "Shape control of CdSe nanocrystals" Nature 404,
59-61; Puntes et al. (2001) "Colloidal nanocrystal shape and size
control: The case of cobalt" Science 291, 2115-2117; U.S. Pat. No.
6,306,736 to Alivisatos et al. (Oct. 23, 2001) entitled "Process
for forming shaped group III-V semiconductor nanocrystals, and
product formed using process"; U.S. Pat. No. 6,225,198 to
Alivisatos et al. (May 1, 2001) entitled "Process for forming
shaped group II-VI semiconductor nanocrystals, and product formed
using process"; U.S. Pat. No. 6,036,774 to Lieber et al. (Mar. 14,
2000) entitled "Method of producing metal oxide nanorods"; U.S.
Pat. No. 5,897,945 to Lieber et al. (Apr. 27, 1999) entitled "Metal
oxide nanorods"; U.S. Pat. No. 5,997,832 to Lieber et al. (Dec. 7,
1999) "Preparation of carbide nanorods"; Urbau et al. (2002)
"Synthesis of single-crystalline perovskite nanowires composed of
barium titanate and strontium titanate" J. Am. Chem. Soc., 124,
1186; and Yun et al. (2002) "Ferroelectric Properties of Individual
Barium Titanate Nanowires Investigated by Scanned Probe Microscopy"
Nanoletters 2, 447.
[0096] Growth of branched nanowires (e.g., nanotetrapods, tripods,
bipods, and branched tetrapods) is described in, e.g., Jun et al.
(2001) "Controlled synthesis of multi-armed CdS nanorod
architectures using monosurfactant system" J. Am. Chem. Soc. 123,
5150-5151; and Manna et al. (2000) "Synthesis of Soluble and
Processable Rod-, Arrow-, Teardrop-, and Tetrapod-Shaped CdSe
Nanocrystals" J. Am. Chem. Soc. 122, 12700-12706.
[0097] Synthesis of nanoparticles is described in, e.g., U.S. Pat.
No. 5,690,807 to Clark Jr. et al. (Nov. 25, 1997) entitled "Method
for producing semiconductor particles"; U.S. Pat. No. 6,136,156 to
El-Shall, et al. (Oct. 24, 2000) entitled "Nanoparticles of silicon
oxide alloys"; U.S. Pat. No. 6,413,489 to Ying et al. (Jul. 2,
2002) entitled "Synthesis of nanometer-sized particles by reverse
micelle mediated techniques"; and Liu et al. (2001) "Sol-Gel
Synthesis of Free-Standing Ferroelectric Lead Zirconate Titanate
Nanoparticles" J. Am. Chem. Soc. 123, 4344. Synthesis of
nanoparticles is also described in the above citations for growth
of nanocrystals, nanowires, and branched nanowires, where the
resulting nanostructures have an aspect ratio less than about
1.5.
[0098] Synthesis of core-shell nanostructure heterostructures,
namely nanocrystal and nanowire (e.g., nanorod) core-shell
heterostructures, are described in, e.g., Peng et al. (1997)
"Epitaxial growth of highly luminescent CdSe/CdS core/shell
nanocrystals with photostability and electronic accessibility" J.
Am. Chem. Soc. 119, 7019-7029; Dabbousi et al. (1997) "(CdSe)ZnS
core-shell quantum dots: Synthesis and characterization of a size
series of highly luminescent nanocrysallites" J. Phys. Chem. B 101,
9463-9475; Manna et al. (2002) "Epitaxial growth and photochemical
annealing of graded CdS/ZnS shells on colloidal CdSe nanorods" J.
Am. Chem. Soc. 124, 7136-7145; and Cao et al. (2000) "Growth and
properties of semiconductor core/shell nanocrystals with InAs
cores" J. Am. Chem. Soc. 122, 9692-9702. Similar approaches can be
applied to growth of other core-shell nanostructures.
[0099] Growth of nanowire heterostructures in which the different
materials are distributed at different locations along the long
axis of the nanowire is described in, e.g., Gudiksen et al. (2002)
"Growth of nanowire superlattice structures for nanoscale photonics
and electronics" Nature 415, 617-620; Bjork et al. (2002)
"One-dimensional steeplechase for electrons realized" Nano Letters
2, 86-90; Wu et al. (2002) "Block-by-block growth of
single-crystalline Si/SiGe superlattice nanowires" Nano Letters 2,
83-86; and U.S. patent application 60/370,095 (Apr. 2, 2002) to
Empedocles entitled "Nanowire heterostructures for encoding
information." Similar approaches can be applied to growth of other
heterostructures.
Example Embodiments for Transferring Nanowires
[0100] Embodiments for applying nanostructures such as nanowires to
surfaces are described in this section. In embodiments, one or more
nanowires are provided proximate to an electrode pair on a transfer
surface. The electrode pair is energized, whereby the nanowires
become associated with the electrode pair. Subsequently, the
nanowires are deposited from the electrode pairs to a destination
surface.
[0101] The term "positioning" as used throughout refers to the
alignment and association, as well as the deposition or coupling,
of nanowires onto a surface, for example, an electrode pair.
Positioning includes nanowires that are both aligned and
non-aligned. The term "aligned" nanowires as used throughout refers
to nanowires that are substantially parallel or oriented in the
same or substantially same direction of one another (i.e. the
nanowires are aligned in the same direction, or within about
45.degree. of one another). The nanowires of the present invention
are aligned such that they are all substantially parallel to one
another and substantially perpendicular to each electrode of an
electrode pair (e.g., aligned parallel to an axis through both
electrodes) (though in additional embodiments, they can be aligned
parallel to an electrode). Positioning of nanowires onto an
electrode pair includes positioning the nanowires such that the
nanowires span the electrode pair. In embodiments in which the
nanowires are longer than the distance separating two electrodes of
an electrode pair, the nanowires may extend beyond the
electrodes.
[0102] Methods for providing nanowires for use in the methods and
systems of the present invention are well known in the art. In an
embodiment, the nanowires are provided in a suspension, which is a
plurality of nanowires suspended in a liquid. In an embodiment, the
liquid is an aqueous media, such as water or a solution of water,
ions (including salts), and other components, for example
surfactants. Additional examples of liquids suitable for preparing
nanowire suspensions include, but are not limited, organic
solvents, inorganic solvents, alcohols (e.g., isopropyl alcohol)
(IPA), etc.
[0103] As used herein the phrase "proximate to an electrode pair"
as it relates to providing the nanowires means that the nanowires
are provided or positioned such that they can be acted upon by an
electric field generated at the electrode pair. This is a distance
from the electrode pair such that they can be associated with the
electrodes. In example embodiments, the nanowires are provided such
that they are at distance of less than about 10 mm from the
electrode pairs. For example, the nanowires may be provided such
that they are less than about 100 .mu.m, less than about 50 .mu.m,
or less than about 1 .mu.m from the electrode pair.
[0104] In embodiments, the present invention provides a system or
apparatus for nanostructure alignment and deposition. For example,
FIG. 2 shows a nanostructure transfer system 200, according to an
example embodiment of the present invention. As shown in FIG. 2,
transfer system 200 includes a nanostructure print head 202,
nanostructure(s) 204, and a destination substrate 212.
Nanostructure print head 202 is a body configured to receive
nanostructure(s) 204, and to transfer nanostructure(s) 204 to
substrate 212. As shown in FIG. 2, nanostructure print head 202 has
a transfer surface 206 and includes an electrode pair 208.
Substrate 212 has a surface 210, referred to as a "destination
surface" for receiving nanostructure(s) 204. Electrode pair 208 is
located on transfer surface 206. Nanostructure(s) 204 are received
by electrode pair 208 of transfer surface 206, for transfer to
destination surface 210. Nanostructure(s) 204 can include any of
the nanostructure types mentioned elsewhere herein, including one
or more nanowires. Further description of the components of
transfer system 200 is provided further below.
[0105] FIG. 3 shows a flowchart 300 providing example steps for
transferring nanostructures, according to example embodiments of
the present invention. For example, nanostructure print head 202 of
FIG. 2 can be used to transfer nanostructure(s) 204 according to
flowchart 300. For illustrative purposes, flowchart 300 is
described as follows with respect to FIGS. 2 and 4-6, which show
various block diagrams of embodiments of the present invention.
Other structural and operational embodiments will be apparent to
persons skilled in the relevant art(s) based on the following
discussion. Not all steps of flowchart 300 are necessarily
performed in all embodiments.
[0106] Flowchart 300 begins with step 302. In step 302, at least
one nanostructure is provided proximate to an electrode pair. For
example, as shown in FIG. 2, nanostructure(s) 204 are provided
proximate to electrode pair 208. For instance, nanostructure(s) 204
may be present in a solution which flows in contact with electrode
pair 208, to enable nanostructure(s) 204 to be positioned proximate
to electrode pair 208. Alternatively, nanostructure(s) 204 may be
provided proximate to electrode pair 208 in other ways.
[0107] In step 304, an electric field is generated by electrodes of
the electrode pair to associate one or more nanostructures with the
electrodes. For instance, an electrical potential may be coupled to
electrode pair 208 to generate the electric field. The electric
field generated by electrode pair 208 may be used to associate
nanostructure(s) 204 with electrode pair 208 that are proximately
located to electrode pair 208. As shown in FIG. 4, nanostructures
204 are associated with electrode pair 208. In an embodiment,
associated nanostructure(s) 204 are held suspended at a distance
from transfer surface 206 by the electric field. Example
embodiments for generating an electric field by an electrode pair
to associate nanostructures are described in further detail
below.
[0108] In step 306, the electrode pair is aligned with a region of
the destination surface. For example, as shown in FIG. 5, electrode
pair 208 is aligned with destination surface 210, by nanostructure
print head 202, which is moved towards destination surface 210
(e.g., in a direction shown by a dotted arrow in FIG. 5). In an
embodiment, electrode pair 208 is aligned in contact with
destination surface 210. In another embodiment, electrode pair 208
is aligned adjacent to destination surface 210, a short distance
away from destination surface 210. Electrode pair 208 may be
aligned with any region of surface 210, including a generally open
region (i.e., no contacts on surface 210 are required), a region
having electrical contacts corresponding to electrode pair 208, or
other region. Electrode pair 208 is aligned with a region of
surface 210 on which nanostructure(s) 204 are to be positioned.
[0109] In step 308, the one or more nanostructures are deposited
from the electrode pair to the region. Nanostructure(s) 204 may be
deposited on destination surface 210 in a variety of ways. Various
example embodiments for depositing nanostructures on a surface are
described in detail below.
[0110] In step 310, the electrode pair is removed from alignment
with the region of the surface. For example, as shown in FIG. 6,
nanostructure print head 202 is moved away from destination surface
210 (e.g., in a direction shown by dotted arrow in FIG. 6).
Nanostructure(s) 204 remain deposited on surface 210. Nanostructure
print head 202 can subsequently be used to repeat performing
flowchart 300 for the same region of surface 210, a different
region of surface 210, and/or a surface of a structure other than
substrate 212, to deposit further nanostructures.
[0111] Detailed example embodiments for nanostructure transfer
system 200 and for performing flowchart 300 are described as
follows. The embodiments are described below with respect to
nanowires. These embodiments are provided for illustrative
purposes, and are not intended to be limiting. It will be
understood by persons skilled in the relevant art(s) that these
embodiments may be used to transfer other types of nanostructures
than just nanowires. Furthermore, these various embodiments may be
adapted and/or combined in a variety of ways, as would be known to
persons skilled in the relevant art(s) from the teachings
herein.
[0112] FIG. 7 shows a nanowire print head 702, which is an example
of nanostructure print head 202 shown in FIG. 2, according to an
embodiment of the present invention. As shown in FIG. 7, nanowire
print head 702 includes electrode pair 208 on transfer surface 206.
Transfer surface 206 may be a surface of a substrate or other
structure of print head 702 onto which electrode pair 208 is formed
(e.g., patterned, plated, etc.). Electrode pair 208 includes a
first electrode 704 and a second electrode 706. Transfer surface
206 may be formed of any suitable material, such as a semiconductor
wafer or dielectric material. Example suitable materials include,
but are not limited to Si, SiO.sub.2, GaAs, InP, and other
semiconductor materials described herein. Exemplary materials for
use as first and second electrodes 704 and 706 include, but are not
limited to, Al, Mo (Moly electrodes), Cu, Fe, Au, Ag, Pt, Cr/Au,
doped polysilicon, etc. Electrodes for use in the practice of the
present invention can also further comprise an oxide coating or
other layer on their surface, if desired. Any suitable orientation
or pattern of first and second electrodes 704 and 706 can be used.
Note that in embodiments, one or more additional electrodes may be
positioned on print head 702 (e.g., between electrodes 704 and
706). Such additional electrodes may be configured to modify an
attractive or repulsive force (e.g., an electrostatic force)
between the nanowires associated with print head 702 and transfer
surface 206 and/or a destination surface.
[0113] Nanowires may be provided proximate to first and second
electrodes 704 and 706 in a variety of ways according to step 302
of flowchart 300. For example, FIG. 8 shows a portion of a nanowire
transfer system 800, according to an embodiment of the present
invention. As shown in FIG. 8, transfer system 800 includes print
head 702 and a solution container 802. Container 802 contains a
solution 804 that includes a plurality of nanowires 806, which may
be referred to as a "nanowire suspension." In the embodiment of
FIG. 8, transfer surface 206 of print head 702 is temporarily moved
(e.g., "dipped") into solution 804 to enable nanowires 806 to
become proximate to electrode pair 208, according to step 302 of
flowchart 300.
[0114] FIG. 9 shows a portion of a nanowire transfer system 900,
according to an alternative embodiment of the present invention. As
shown in FIG. 9, transfer system 900 includes print head 702 and
solution container 802. Container 802 contains solution 804 that
includes plurality of nanowires 806. In the embodiment of FIG. 9,
transfer surface 206 (and the rest of print head 702) resides in
solution 804, to enable nanowires 806 to become proximate to
electrode pair 208, according to step 302 of flowchart 300.
[0115] Note that although electrode pair 208 is shown in FIG. 9 as
facing upward in solution 804, and is shown in FIG. 8 as facing
downward, print head 702 may be oriented in other ways so that
electrode pair 208 may face in other directions, including upwards,
downwards or sideways.
[0116] Nanowires 806 may be any suitable nanowire type described
herein or otherwise known. For example, nanowires 806 may have a
semiconductor core and one or more shell layers disposed about the
core (i.e., the shell layers surround the core) (such as shown in
FIGS. 1B and 1C). Examples semiconductor materials and shell
materials include those described elsewhere herein. In an example
embodiment, the core includes silicon (Si) and at least one of the
shell layers, such as the outermost shell layer (i.e., the shell
layer that is in contact with the external environment) includes a
metal, such as TaAlN or WN. Additional examples of metal shell
layers include those described elsewhere herein. Further exemplary
nanowires include core:shell (CS) nanowires (e.g., SiO.sub.2),
core:shell:shell (CSS) nanowires (e.g., SiO.sub.2:metal), and
core:no oxide shell:metal shell nanowires (CNOS) (e.g.,
Si:metal).
[0117] In an embodiment, container 802 receives a flow of solution
804 containing nanowires 806. For instance, FIG. 10 shows a block
diagram of a nanowire solution flow system 1000, according to an
example embodiment of the present invention. As shown in FIG. 10,
flow system 1000 includes a nanowire suspension source reservoir
1002, container 802, and a nanowire suspension collection chamber
1004. Nanowire suspension source reservoir 1002 is a tank or other
type of reservoir that contains a supply of solution 804. Nanowires
806 may be introduced into solution 804 in reservoir 1002 to form
the suspension, if desired. Solution 804 may be any suitable type
of liquid for containing nanowires 806, including water, isopropyl
alcohol (IPA), other liquids described herein, etc.
[0118] As shown in FIG. 10, nanowire suspension source reservoir
1002 outputs a nanowire suspension flow 1006 that is received by
container 802. Nanowire suspension flow 1006 may be supplied by
reservoir 1002 to container 802 by one or more flow channels,
pipes, valves, etc. After enabling the suspension to interact with
print head 702, container 802 outputs a residual nanowire
suspension flow 1008 that is received by nanowire suspension
collection chamber 1004. Nanowire suspension collection chamber
1004 is a tank or other type of reservoir. The residual nanowire
suspension flow received in chamber 1004 may be filtered and/or
supplied back to source reservoir 1002 for recirculation through
system 1000, may have residual nanowires recovered therefrom, may
be discarded, etc.
[0119] Thus, in the embodiments described above, one or more
nanowires 806 are provided by providing a suspension of nanowires
(e.g., a nanowire "ink") to electrode pair 208. As represented in
FIG. 10, a nanowire suspension is provided by flowing a solution
containing nanowires against an electrode pair on a transfer
surface. As nanowires 806 are provided, the suspension flow helps
to align the nanowires in the direction of the flow.
[0120] In an embodiment, container 802 can be stirred, vibrated, or
otherwise moved to maintain a homogeneous suspension of nanowires
806. In another embodiment, where a stratified suspension of
nanowires is desired, gravity, electric fields and/or an overflow
by a nanowire-free solvent of similar or lower density can be used
to create stratification. A stratified suspension of nanowires may
be used in a variety of ways. For example, print head 702 may be
positioned in a high nanowire-density region of the stratified
suspension for deposition of nanowires, and subsequently positioned
in a lower density, "clean solvent" region for removal of excess
nanowires.
[0121] Additional methods for providing nanowires to an electrode
pair are well known in the art, and include, but are not limited
to, spray coaters, spray painting, meniscus coater, dip-coater,
bar-coater, gravure coater, Meyer rod, doctor blade, extrusion,
micro-gravure, web coaters, doctor blade coaters, in-line or ink
jet printers.
[0122] As described above, a variety of configurations for
electrode pair 208 may be used in embodiments. For example,
electrode pair 208 may be fixed position electrodes. In another
embodiment, electrode pair 208 may be configured to enable
compliance with a destination surface to which they may be applied.
For instance, FIG. 11 shows a plan view of an example print head
1100, according to an embodiment of the present invention. Print
head 1100 has a transfer surface 1102 having first and second
cantilevers 1104 and 1106 that mount electrode pair 208. FIG. 12
shows a side cross-sectional view of print head 1100. As shown in
FIGS. 12 and 13, first and second cantilevers 1104 and 1106 are
generally coplanar and coaxial bodies, having adjacently positioned
movable ends, and oppositely positioned fixed ends. First
cantilever 1104 has a raised end portion 1112 on its movable end,
and second cantilever 1106 has a raised end portion 1114 on its
movable end. First electrode 704 is formed on raised end portion
1112 of first cantilever 1104, and second electrode 706 is formed
on raised end portion 1114 of second cantilever 1106. A first
electrical conductor 1108 (e.g., a metal trace) is formed on first
cantilever 1104 to electrically couple first electrode 704 to an
external circuit, and a second electrical conductor 1110 (e.g., a
metal trace) is formed on second cantilever 1106 to electrically
couple second electrode 706 to an external circuit. For example,
first and second electrical conductors 1110 may electrically couple
first and second electrodes 704 and 706 to a DC and/or AC
electrical signal source.
[0123] First and second cantilevers 1104 and 1106 are not
substantially flexible in the plane of transfer surface 1102, but
are flexible in a direction normal to the plane of transfer surface
1102 (shown as a Z-axis in FIG. 12). Thus, when first and second
electrodes 704 and 706 are positioned in contact with a surface
(e.g., destination surface 210), the free ends of first and second
cantilevers 1104 and 1106 can flex into a gap 1202 below their free
ends, to provide compliance to protect first and second electrodes
704 and 706 from damage, and to aid in complying with a non-level
destination surface.
[0124] Cantilevers 1104 and 1106 may be any type and configuration
of cantilever. In an embodiment, cantilevers 1104 and 1106 are
micro-electromechanical system (MEMS) cantilevers.
[0125] According to step 304 of flowchart 300 (FIG. 3), an electric
field is generated by electrodes of an electrode pair to associate
nanostructures with the electrodes. FIG. 13 shows a nanowire
transfer system 1300 that can be used to perform step 304 of
flowchart 300 (FIG. 3), according to an example embodiment of the
present invention. As shown in FIG. 13, system 1300 includes a
voltage source 1302. Voltage source 1302 is a signal/waveform
generator coupled to electrode pair 208 by electrical signal 1304.
Voltage source 1302 generates electrical signal 1304 as a direct
current (DC) and/or alternating current (AC) signal to cause
electrode pair 208 to generate an electric field. For example, FIG.
14 shows transfer system 800 of FIG. 8, where an electric field,
represented between first and second electrodes 704 and 706 by
arrow 1402, is generated by application of a voltage to electrode
pair 208. Electric field 1402 is generated between electrodes 704
and 706 of electrode pair 208 by energizing electrode pair with
electrical signal 1304 to associate at least some of nanowires 806
with electrode pair 208. It should be noted that electric field
1402 can be generated before, after, or during the period of
nanowire producing/introduction into container 802. As used herein,
the terms "electric field" and "electromagnetic field" are used
interchangeably and refer to the force exerted on charged objects
in the vicinity of an electric charge. As used herein, "energizing
the electrode pair" refers to any suitable mechanism or system for
providing an electric current to the electrodes such that an
electric field is generated between electrodes of an electrode
pair.
[0126] Energizing electrode pair 208 to generate electric field
1402 can be performed during part or all of a nanowire alignment
and deposition process. For example, electrode pair 208 may remain
energized during step 306 of flowchart 300 (alignment of print
head) and during a portion or all of step 308 of flowchart 300
(deposition of nanowires). In an example embodiment, electric field
1402 is generated by coupling (e.g., using wires or other
connection) first electrode 704 to a positive electrode terminal of
voltage source 1302, and coupling second electrode 706 to a
negative electrode terminal of voltage source 1302. When an
electric current is switched on and supplied by electrical signal
1304, the negative and positive terminals transfer charge to
electrodes 704 and 706 positioned on transfer surface 206, thereby
generating electric field 1402 between electrodes 704 and 706 of
electrode pair 208. In embodiments, electric field 1402 can be
constant electric field, a pulsed electric field such as a pulsed
AC electric field, or other electric field type.
[0127] The energizing of electrode pair 208 to create electric
field 1402 can also be caused by supplying an electromagnetic wave
to electrode pair 208. As is well known in the art, waveguides of
various dimensions and configurations (e.g., cylindrical,
rectangular) can be used to direct and supply an electromagnetic
wave (see e.g., Guru, B. S. et al., "Electromagnetic Field Theory
Fundamentals," Chapter 10, PWS Publishing Company, Boston, Mass.
(1998)). Operation frequencies of waveguides for use in the
practice of the present invention are readily determined by those
of skill in the art, and may be in the range of about 100 MHz to 10
GHz, about 1 GHz-5 GHz, about 2-3 GHz, about 2.5 GHz, or about 2.45
GHz, for example.
[0128] As is further described below, as nanowires 806 encounter an
AC electric field 1402 generated between electrodes 704 and 706, a
field gradient results. A net dipole moment is produced in
proximate nanowires 806 (e.g., nanowire 806a in FIG. 14), and the
AC field exerts a torque on the dipole, such that proximate
nanowires align parallel to the direction of the electric field.
For example, FIG. 15 shows nanowire 806a having been aligned by
electric field 1402 parallel to electric field 1402 in association
with electrode pair 208.
[0129] In embodiments, first and second electrodes 704 and 706 are
separated by a distance that is less than, equal to, or greater
than a long axis length of nanowires 806. Nanowires 806 of any
length can be aligned and positioned using the methods of the
present invention. In an embodiment, the distance between
electrodes of an electrode pair is such that the nanowires extend
just beyond the first edge of the electrode. In an embodiment,
nanowires 806 extend just beyond a first edge and into a middle of
each electrode, with tens of nanometers to several microns
overlapping the electrode material at the end of a nanowire 806.
Nanowires 806 that are shorter than the distance between electrodes
704 and 706 may be able to couple to only one electrode in a pair
(if they couple at all), and thus may be removed during subsequent
removing phases if desired. Similarly, nanowires 806 that are
substantially longer than the distance between electrodes 704 and
706 hang over one or more of electrodes 704 and 706, and may be
removed during subsequent removing phases (larger exposed surface
area). Thus, this embodiment additionally provides a way to
preferentially select nanowires 806 of a particular length from a
suspension of a range of nanowire sizes, and align and deposit them
onto an electrode pair 208. Embodiments may also associate and
couple nanowires 806 that are "straight" rather than bent or
crooked. Hence, such embodiments provide an added benefit of
depositing preferably straight nanowires 806, rather than less
preferred bent or crooked nanowires 806.
[0130] In addition to aligning the nanowires parallel to an AC
electric field, the field gradient exerts a dielectrophoretic force
on proximate nanowires 806, attracting them toward electrode pair
208. FIG. 16 shows a force 1602 attracting nanowire 806a towards
electrode pair 208 of print head 702. In an embodiment, force 1602
is a dielectrophoretic force. The gradient is highest at electrode
pair 208, exerting an increasing attraction toward the electrodes.
An electric double-layer is produced at the surface of each
electrode of electrode pair 208, such that oppositely charged ions
are present at each electrode. In the presence of electric field
1402, the ions migrate away from each electrode and initially
toward nanowire 806a hovering proximately nearby (e.g., above or
below). As ions approach oppositely charged nanowire 806a, the ions
are repulsed by the like charge and then directed back toward the
respective electrode resulting in a circulating pattern of ions.
Liquid that is present (i.e., the nanowire suspension) is also
circulated, generating an electro-osmotic force that opposes the
dielectrophoretic force attracting nanowire 806a to the electrodes.
Thus, in an embodiment, a force 1606 shown in FIG. 16 may be an
osmotic force. As forces 1602 and 1606 reach an equilibrium (or
relative equilibrium), nanowire 806a is held in place such that it
becomes associated with electrode pair 208. As used herein the
terms "associated" and "pinned" are used to indicate that nanowires
(such as nanowire 806a) are in such a state that the
electro-osmotic force and the dielectrophoretic force are at
equilibrium, such that there is no or little net movement of the
nanowires away from electrode pair 208 (i.e., normal or
substantially normal to transfer surface 206 and electrode pair
208). This is also called the "association phase" throughout.
[0131] Furthermore, in an embodiment, charge values of nanowires
806 and transfer surface 206 affect association or pinning of
nanowires to electrode pair 208. For example, FIG. 16 shows print
head 702 having associated nanowire 806a (additional nanowires not
shown may also be associated). As shown in FIG. 16, transfer
surface 206 may have a layer 1604 that provides a surface charge to
transfer surface 206, such as an oxide layer. The charge polarity
of layer 1604 can be selected to attract or repel nanowire 806a, as
desired. For example, layer 1604 can provide a negative surface
charge to transfer surface 206 that results in a repulsive force on
nanowire 806a, which may also have a negative surface charge (e.g.,
in isopropyl alcohol). Thus, force 1606 repelling nanowire 806a in
FIG. 16 may include an electrostatic repulsive force that results
from a same charge polarity of nanowire 806a and layer 1604.
[0132] In the associated, or pinned state, the nanowires are
aligned parallel to the electric field, but are sufficiently mobile
along the electrode edges (i.e. in a plane just above the surface
of the electrodes). For example, FIGS. 17 and 18 show plan and side
cross-sectional views, respectively, of electrode pair 208 on
cantilevers 1104 and 1106 of FIG. 11. As shown in FIGS. 17 and 18,
a plurality of nanowires 1702 is associated, or pinned, with first
and second electrodes 704 and 706. Nanowires 1702 are pinned at a
distance 1802 from electrode pair 208. The amount of distance 1802
depends on a variety of factors, including a strength of the
applied electric field 1402, a frequency of electric field 1402, a
strength of charge of nanowires 1702, a strength of charge of layer
1604, etc.
[0133] In the associated or pinned state, nanowires 1702 are free
to rearrange, migrate and/or align along the length of the
electrodes 704 and 706. Nanowires 1702 that are already
substantially aligned with electric field 1402 will tend to migrate
along electrode pair 208 until contacting, and/or being repelled
by, a nearest neighbor nanowire. Nanowires 1702 that are not
substantially aligned will tend to migrate such that they become
aligned as they contact, and/or are repelled by, nearest neighbor
nanowires and, an equilibrium between the various forces acting on
nanowires 1702 is reached. The lateral mobility (i.e., along
electrode pairs 208, perpendicular to a direction of electric field
1402) of nanowires 1702 allows them to accommodate a chronological
sequence of alignment and association events without giving rise to
nanowire clumping. That is, as nanowires are continuously supplied
to electrode pair 208 (i.e., from a suspension) additional
nanowires are able to associate with the electrodes, as the
nanowires that are previously associated are freely mobile such
that they move out of the way to accommodate additional
nanowires.
[0134] For further example description regarding the association of
nanowires with electrode pairs, various nanowire densities,
alternating current frequencies, modulating of the electric field,
"locking" nanowires to an electrode pair, etc., refer to co-pending
U.S. Appl. No. 60/857,765, filed Nov. 9, 2006, titled "Methods for
Nanowire Alignment and Deposition," which is incorporated by
reference herein in its entirety.
[0135] Following the associating of nanowires 1702 with electrodes
704 and 706, uncoupled nanowires can then be removed from electrode
pair 208 so as to substantially eliminate nanowires that are not
fully aligned, not fully coupled, overlapped, crossing, or
otherwise not ideally coupled to electrode pair 208. Nanowires that
are to be removed following the coupling phase are described herein
as "uncoupled nanowires." Any suitable method for removing
uncoupled nanowires can be used. For example, the uncoupled
nanowires can be removed using tweezers (e.g., optical tweezers,
see, e.g., U.S. Pat. Nos. 6,941,033, 6,897,950 and 6,846,084, the
disclosures of each of which are incorporated herein by reference
in their entireties) or similar instrument, or by shaking or
physically dislodging the uncoupled nanowires. Suitably, uncoupled
nanowires are removed by flushing away the nanowires. As used
herein, the term "flushing away" includes processes where a fluid
(either gaseous or liquid phase) is flowed over or around the
nanowires so as to remove them from the electrode pairs. Nanowires
that are crossed can be uncrossed using a suitably modulated
electric field, and a third electrode can be used to remove
"uncoupled nanowires," such as dielectrophoretically or
electroosmotically. Uncoupled nanowires can also be removed
inertially, and by other techniques.
[0136] According to step 306 of flowchart 300 (FIG. 3), the
electrode pair is aligned with a region of the destination surface.
FIG. 19 shows a print head alignment system 1900 that can be used
to perform step 306 for a nanowire transfer system, according to an
example embodiment of the present invention. As shown in FIG. 19,
system 1900 includes an alignment mechanism 1902 that is coupled to
print head 702. Alignment mechanism 1902 is configured to move
print head 702 such that electrode pair 208 is aligned with a
designated nanowire transfer region 1904 on destination surface 210
of substrate 212. Alignment mechanism 1902 may be configured to
move print head 702 so that electrode pair 208 is adjacent to but
not in contact with region 1904, and/or to move print head 702 so
that electrode pair 208 contacts region 1904. For example,
alignment mechanism 1902 may include a motor (e.g., a linear motor)
or other movement mechanism for moving print head 702 to region
1904. Furthermore, alignment mechanism 1902 may include position
detecting sensors for detecting a position of print head 702 and/or
substrate 212 to accurately position print head 702 with respect to
region 1904. Example position detecting sensors may include optical
sensors (e.g., vision systems), proximity sensors, mechanical
sensors, etc., to detect relative position.
[0137] Substrate 212 may be any type of structure suitable for
placement of nanostructures. For example, substrate 212 may be
formed of a variety of materials, including a semiconductor
material (e.g., silicon, GaAs, etc.), a polymer (e.g., a plastic
material), glass, a ceramic material, a composite material, a
printed circuit board (PCB), etc.
[0138] Note that FIG. 19 shows an embodiment where electrode pair
208 and a plurality of associated nanowires 1702 are covered in a
fluid membrane 1906. For example, print head 702 may have been
dipped in solution 804, as shown in FIG. 8, to have nanowires 1702
associated with electrode pair 208, as shown in FIGS. 14 and 15.
Subsequently, print head 702 is withdrawn from solution 804.
However, fluid membrane 1906 remains on transfer surface 206 to
keep nanowires 1702 wet. In this manner, nanowires 1702 remain
associated with electrode pair 208, including being aligned and
positioned relative to first and second electrodes 704 and 706. For
example, transfer surface 206 may be coated with a hydrophilic
material that enables fluid membrane 1906 to stick to transfer
surface 206. In embodiments, region 1904 on destination surface 210
may also be coated with a solution or may alternatively be
relatively dry.
[0139] FIG. 20 shows print head 702 having been aligned with region
1904 by alignment mechanism 1902 (e.g., in the direction of the
downward dotted arrow shown in FIG. 20). As shown in FIG. 20, first
and second electrodes 704 and 706 physically hold nanowires 1702 in
contact with region 1904. Furthermore, nanowires 1702 substantially
retain their alignment and position on electrode pair 208 while
making contact with region 1904 due to the action of electric field
1402 and other forces acting on nanowires 1702.
[0140] FIGS. 21 and 22 show print head 702 of FIG. 9 being aligned
with destination surface 210, according to an example embodiment of
the present invention. Nanowires 806 are shown removed from
solution 804 in FIGS. 21 and 22, although they may alternatively
still be present in solution 804. As shown in FIG. 21, substrate
212 and print head 702 are both submerged in solution 804.
Nanowires 1702 are shown associated with electrodes 704 and 706
(e.g., according to step 304 of flowchart 300). As shown in FIG.
22, print head 702 has been aligned with region 1904 (e.g., by
alignment mechanism 1902, not shown in FIGS. 21 and 22). First and
second electrodes 704 and 706 physically hold nanowires 1702 in
contact with region 1904 in FIG. 22. Furthermore, nanowires 1702
substantially retain their alignment and position on electrode pair
208 while making contact with region 1904, as described above.
[0141] Note that in an embodiment, as shown in FIG. 23, one or more
spacers or spacing members 2302 may be present on transfer surface
206 (and/or on destination surface 210) to hold transfer surface
206/electrode pair 208 at a predetermined distance from destination
surface 210, and/or to reduce an impact between electrodes 704 and
706 and destination surface 210 when making contact. This may
further be useful in aiding associated nanowires 1702 from losing
their alignment and position when transfer surface 206 is being
aligned with destination surface 210 according to step 306. Spacing
members 2302 may be used in combination with any embodiment
described herein. Spacing members 2302 may have any height, as
determined for a particular application. For example, in an
embodiment, a spacing member 2302 has a height of approximately 100
.mu.m.
[0142] FIGS. 24 and 25 show examples of print head alignment for
the configuration of print head 1100 of FIGS. 11, 17, and 18. As
shown in FIG. 24, print head 1100 has been aligned with region 1904
(e.g., by alignment mechanism 1902, not shown in FIGS. 24 and 25).
First and second electrodes 704 and 706 physically hold nanowire
1702 in contact with region 1904 in FIG. 22. Furthermore, nanowires
1702 substantially retain their alignment and position on electrode
pair 208 while making contact with region 1904, as described
above.
[0143] In FIG. 25, substrate 212 is not planar, but instead has an
uneven surface. A portion of region 1904 corresponding to second
electrode 706 is higher than a portion of region 1904 corresponding
to first electrode 704. Thus, second cantilever 1106 of print head
1100 flexes (e.g., in an upward direction indicated by a dotted
arrow) in order for second electrode 706 to maintain contact with
region 1904. Furthermore, by second cantilever 1106 flexing, first
electrode 704 is able to maintain holding its respective ends of
nanowires 1702 on region 1904.
[0144] Note that in an embodiment where a print head is aligned
with a destination surface in solution, the solution between the
print head and destination surface will be displaced during
alignment. If the solution is displaced laterally, this may cause
problems with displacing associated nanowires, with increasing an
area of the print head, and/or further problems. FIG. 26 shows a
nanowire transfer system 2600, according to an example embodiment
of the present invention. System 2600 is similar to system 1300
shown in FIG. 13, with the addition of a vacuum source 2602.
Furthermore, transfer surface 206 includes one or more vacuum ports
2604 coupled to vacuum source 2602. Vacuum source 2602 applies a
vacuum or suction 2606 through vacuum port 2604 to the volume
between transfer surface 206 and substrate 212 to remove excess
solution. Thus, as transfer surface 206 and substrate 212 approach
each other, excess solution can be removed to prevent displacement
of associated nanowires, etc.
[0145] FIG. 27 shows an example plan view of transfer surface 206,
according to an example embodiment of the present invention. As
shown in FIG. 27, transfer surface 206 includes first and second
electrodes 704 and 706, and a plurality of vacuum ports
2604a-2604c. In the example of FIG. 27, three vacuum ports
2604a-2604c are shown. First vacuum port 2604a is positioned on
transfer surface 206 adjacent to first electrode 704. Second vacuum
port 2604b is positioned on transfer surface 206 between first and
second electrodes 704 and 706. Third vacuum port 2604c is
positioned on transfer surface 206 adjacent to second electrode
706. Any number of vacuum ports 2604 may be present, and may be
distributed on transfer surface 206 as desired. In the example of
FIG. 27, vacuum ports 2604a-2604c are rectangular shaped. In other
embodiments, vacuum ports 2604 may have other shapes, including
round, square, etc.
[0146] According to step 308 of flowchart 300 (FIG. 3), one or more
nanostructures are deposited from the electrode pair to the region.
Nanowires may be deposited on destination surface 210 in a variety
of ways. Various example embodiments for depositing nanowires on a
surface are described as follows.
[0147] For example, FIG. 28 shows a nanowire transfer system 2800,
according to an embodiment of the present invention. As shown in
FIG. 28, nanowires 2802 are deposited on region 1904 from electrode
pair 208. In the embodiment of FIG. 28, a force 2802 is present
(which may include one or more forces) that attracted nanowires
1702 from print head 702 to destination surface 210 while they are
aligned, and/or repelled nanowires 1702 from print head 702,
overcoming any force(s) that attracted nanowires 1702 to transfer
surface 206 of print head 702. Example forces that may be present
in force 2802 include an electric field (AC and/or DC), a vacuum
force, an electrostatic force, gravity, ultrasonic excitation,
and/or other forces. These and other passive and active forces may
be used to attract/repel nanowires 1702, as would be known to
persons skilled in the relevant art(s). Example embodiments for
utilizing some of these forces are described as follows.
[0148] For example, FIG. 29 shows a transfer system 2900, according
to an embodiment of the present invention. Transfer system 2900 is
generally similar to transfer system 2800 of FIG. 28. However, as
shown in FIG. 29, transfer surface 206 has negatively charged layer
2902 formed thereon. Negatively charged layer 2902 results in a
negative surface charge for transfer surface 206, and thus a DC
repulsive force on nanowires 1702 (which may be negatively
charged). For example, layer 2902 may be an oxide layer. An
electric field generated by electrode pair 208 (e.g., electric
field 1402) is biased with an AC field condition to previously
capture nanowires 1702 from solution, according to step 304 of
flowchart 300 described above.
[0149] Furthermore, as shown in FIG. 29, destination surface 210
has a positively charged layer 2904 formed thereon. For example,
positively charge layer 2904 may be an alumina layer. Positively
charged layer 2904 results in a positive surface charge for
destination surface 210, and thus a DC attractive force on
nanowires 1702. When transfer surface 206 and destination surface
210 are sufficiently close (e.g., in the range of 1 .mu.m to 4
.mu.m), including when they are in contact with each other,
nanowires 1702 transfer onto destination surface 210, as shown in
FIG. 29, because the DC attractive force of layer 2904 overcomes
the attractive force (dielectrophoretic force) caused by the AC
electric field generated by electrode pair 208. In an embodiment,
to enable transfer, the AC electric field may be reduced (e.g., by
voltage source 1302) or entirely removed to reduce or remove the
dielectrophoretic force.
[0150] FIG. 30 shows a plot 3000 of nanowire potential energy as a
function of distance from either transfer surface 206 or
destination surface 210. Transfer surface 206 can have a negatively
charged layer 2902 as an oxide layer and destination surface 210
can have a positively charged layer 2904 as a nitride layer,
according to an embodiment of the present invention. A plot line
3002 represents the potential energy of nanowires suspended in
solution over transfer surface 206 and a plot line 3004 represents
the potential energy of nanowires suspended in solution over
destination surface 210.
[0151] As shown in FIG. 30, at a first plot region 3006
representing a first potential minimum on plot line 3002 for
transfer surface 210, nanowires 1702 are associated (pinned) with
electrode pair 208. The pinned nanowires remain relatively
rigid/aligned without being in contact with a transfer surface. In
the current example, first plot region (first potential minimum)
3006 occurs when transfer surface 206 and destination surface 210
are approximately 1 .mu.m-4 .mu.m apart. At a second plot region
(second potential minimum) 3008 representing a potential minimum on
plot line 3004 for destination surface 210, nanowires 1702 are
attracted to destination surface 210 due to the electrostatic
attraction by the nitride layer. Nanowires 1702 may be "locked" on
destination surface 210 in this manner. Second plot region 3008
occurs when nanowires and destination surface 210 are spaced
approximately 0.1 .mu.m-0.4 .mu.m apart.
[0152] The transfer of nanowires 1702 from transfer surface 206
onto destination surface 210 is achieved by first "weakly" pinning
nanowires 1702 on transfer surface 206 at low electric fields and
low frequencies, "strongly" pinning nanowires 1702 on transfer
surface 206 using low electric fields and high frequencies, moving
transfer surface 206 to close proximity with destination surface
210, and finally releasing nanowires 1702 from potential minimum
3006 of transfer surface 206 by reducing the AC field on electrodes
704 and 706 of transfer surface 206. Due to the electrostatic
repulsion represented by a potential maximum 3010 between nanowires
1702 and transfer surface 206 (e.g. layer 2902 on transfer surface
206) nanowires 1702 move away from transfer surface 206 after
reduction of the AC attractive field. Within the rotational
diffusion time (i.e. time required for nanowires to be rotated by
an angle .theta. from a pre-aligned direction while subjected to
gravity and Brownian motion) nanowires 1702 maintain the desired
alignment determined by the AC field across electrodes 704 and 706
on transfer surface 206. The close proximity (e.g., .about.1 .mu.m)
of the pre-aligned nanowires 1702 in solution to destination
surface 210 enables a transfer onto destination surface 210 due to
the electrostatic attraction represented by potential minimum 3008
(e.g. layer 2904 on destination surface 210). An efficient transfer
of nanowires 1702 is enabled when the rotational diffusion time is
large compared to the translational diffusion time for motion of
nanowires from potential minimum 3006 to potential minimum 3008.
Functional layers on nanowires 1702 and on destination surface 210
can be used to minimize the translational diffusion time without
affecting the rotational diffusion time.
[0153] Note that in an embodiment, ultrasonic excitation/vibration
can be used to enhance the process just described. For example,
FIG. 31A shows a transfer system 3100, according to an embodiment
of the present invention. Transfer system 3100 is generally similar
to transfer system 2900 of FIG. 29, with the addition of ultrasonic
vibration source 3102. Ultrasonic vibration source 3102 includes a
piezoelectric transducer or other ultrasonic vibration source to
ultrasonically vibrate print head 702 and transfer surface 206. In
an embodiment, ultrasonic vibration of print head 702 causes
nanowires to be separated from the transfer head up to
approximately 100 .mu.m, which enables the distance between
transfer surface 206 and destination surface 210 to be larger while
still allowing nanowires 1702 to be deposited on destination
surface 210. The rate at which print head 702 moves toward
destination surface 210 may be high initially and reduced gradually
as print head 702 moves close to destination surface 210. For
example, ultrasonic vibration source 3102 can be activated when
transfer surface 206 approaches within 100 .mu.m of destination
surface 210. This enables depositing of nanowires 1702 to
destination surface 210 (e.g., by gravity, electrostatic
attraction, etc.) sooner (at a larger distance) while better
maintaining the alignment of nanowires 1702 with electrode pair 208
than when electrode pair 208 is moved closer or even contacts
destination surface 210.
[0154] FIG. 31B shows a transfer system 3150, according to an
embodiment of the present invention. Transfer system 3150 is
generally similar to transfer system 3100 of FIG. 31A, except that
an ultrasonic vibration source 3152 is coupled to substrate 212,
rather than ultrasonic vibration source 3102 being associated with
print head 702. Although shown coupled to a bottom surface of
substrate 212, ultrasonic vibration source 3152 can be coupled to
substrate 212 in any manner, including being coupled to the top
surface, or being embedded in substrate 212 Ultrasonic vibration
source 3152 may be secured in an ultrasonic chuck, or other
application mechanism.
[0155] Ultrasonic vibration source 3152 includes a piezoelectric
transducer or other ultrasonic vibration source to ultrasonically
vibrate substrate 212, and thus to ultrasonically vibrate
destination surface 210. Furthermore, when transfer surface 206 and
destination surface 210 are brought near each other, spacers 2302
(on print head 702 and/or substrate 212) contact print head 702 and
destination surface 210 together. Thus, ultrasonic vibration source
3152 also vibrates print head 702 and transfer surface 206. Because
ultrasonic vibration source 3152 vibrates both transfer surface 206
and destination surface 210, they vibrate synchronously, such that
they both vibrate in the same direction simultaneously. This causes
less turbulence than when only one of transfer surface 206 and
destination surface 210 vibrate, and thus nanowires 1702 are better
able to retain their alignment while being transferred (e.g., by
gravity, electrostatic attraction, etc.) from transfer surface 206
to destination surface 210.
[0156] FIG. 31C shows a plot 3170 of an inertial motion of
nanowires in isopropyl alcohol (IPA) solution, according to an
embodiment of the present invention. An X-axis 3172 of plot 3170 is
a displacement amplitude, in centimeters, of destination surface
210 and transfer surface 206 caused by ultrasonic vibration source
3152. A Y-axis 3174 of plot 3170 is a displacement frequency caused
by ultrasonic vibration source 3152. A Z-axis 3176 of plot 3170
shows a resulting displacement amplitude of nanowires 1702 in
.mu.m. A plot surface 3178 indicates generally that as surface
displacement amplitude increases (on X-axis 3172), nanowire
displacement amplitude (on Z-axis 3176) also increases. Likewise,
as displacement frequency (on Y-axis 3174) increases, nanowire
displacement amplitude (on Z-axis 3176) also increases.
[0157] In an example embodiment, transfer surface 206 and/or
destination surface 210 may be ultrasonically vibrated at
relatively high frequency, such as 10 KHz, with a low amplitude,
such as 50-100 microns, to effectively transfer nanowires 1702 from
transfer surface 206 to destination surface 210. A variety of other
combinations of displacement amplitude (X-axis 3172) and
displacement frequency (Y-axis 3174) combinations are apparent from
plot 3170, and may be used to cause wire displacement (Z-axis 3176)
to transfer nanowires, as desired for a particular application.
[0158] FIG. 32 shows an example transfer system 3200, according to
another embodiment of the present invention. Transfer system 3200
is similar to transfer system 2800 of FIG. 28, with the addition of
a vacuum source 3202 that applies a vacuum force 3204 through
vacuum ports 3206 in substrate 212 to attract nanowires 1702 to
destination surface 210. For example, using vacuum force 3204,
vacuum source 3202 draws a solution surrounding nanowires 1702 in
through vacuum ports 3206. The resulting solution flow exerts a
pull on nanowires 1702 toward destination surface 210.
[0159] FIG. 33 shows an example transfer system 3300, according to
another embodiment of the present invention. Transfer system 3300
is similar to transfer system 2800 of FIG. 28, with the addition of
an electric field source 3302 that generates an electric field 3304
to attract nanowires 1702 to destination surface 210. For example,
in an embodiment, electric field source 3302 may generate a DC
electric field for electric field 3304. The DC electric field
(e.g., a positive charge) exerts an attractive force on nanowires
1702 due to the opposite charge of nanowires 1702 (e.g., a negative
charge), causing nanowires 1702 to move. Such movement of nanowires
1702 enables nanowires 1702 to be attracted to destination surface
210 by electric field 3304 and/or other force. In another
embodiment, electric field source 3302 may generate an AC electric
field for electric field 3304 which operates in an analogous
fashion to move nanowires 1702, to enable nanowires 1702 to be
attracted to destination surface 210. In still another embodiment,
a combination of DC and AC electric fields may be used. In an
embodiment, electric field source 3302 is a signal generator,
voltage supply, or other component or device capable of generating
an electric field.
[0160] It is noted that the above described embodiments for
depositing nanowires on a destination surface according to step 308
of flowchart 300 (FIG. 3) may be combined in any manner, as would
be understood by persons skilled in the relevant art(s) from the
teachings herein.
[0161] According to step 310 of flowchart 300 (FIG. 3), the
electrode pair is removed from alignment with the region of the
surface. For example, as shown in FIG. 28, print head 702 may be
moved in the upward direction (shown by dotted arrow) to be removed
from alignment with region 1904. For example, alignment mechanism
1902 (shown in FIG. 19) may be used to move print head 702 from
alignment with region 1904. In an embodiment, a fluid can be
supplied (e.g., through ports 2604 of FIG. 26 and/or ports 3206 of
FIG. 32) between transfer surface 206 and destination surface 210
to provide pressure to move the surfaces apart (e.g., gas or liquid
pressure). In this manner, flowchart 300 of FIG. 3 may be repeated
by print head 702, to associate and deposit further nanowires on
region 1904, on other region(s) of substrate 212, and/or on
alternative surfaces.
[0162] Furthermore, flowchart 300 is adaptable to using multiple
electrode pairs on a single transfer surface to deposit groups of
nanowires on substrates in parallel. For example, FIG. 34 shows a
nanowire transfer system 3400 that includes a print head 3402
having two electrode pairs, according to an embodiment of the
present invention. As shown in FIG. 34, print head 3402 has a
transfer surface 3404 having a first electrode pair 208a and a
second electrode pair 208b. First electrode pair 208a is shown
having associated nanowires 1702a, and second electrode pair 208b
is shown having associated nanowires 1702b. Nanowires 1702a are
designated for deposit on first region 1904a of destination surface
210, and nanowires 1702b are designated for deposit on second
region 1904b of destination surface 210.
[0163] Thus, in an embodiment, each step of flowchart 300 shown in
FIG. 3 may be performed for both of first and second electrode
pairs 208a and 208b in parallel. In step 302, in parallel with
providing nanowires 1702a proximate to first electrode pair 208a,
nanowires 1702b can be provided proximate to second electrode pair
208b. In step 304, in parallel with generating a first electric
field (e.g., electric field 1402 in FIG. 14) using first electrode
pair 208a, a second electric field can be generated using second
electrode pair 208b to associate nanowires 1702b with second
electrode pair 208b. In embodiments, a same electrical signal
(e.g., electrical signal 1304) can be provided to both of first and
second electrode pairs 208a and 208b, or different electrical
signals can be generated and provided.
[0164] In step 306, in parallel with aligning first electrode pair
208a with first region 1904a, second electrode pair 208b can be
aligned with second region 1904b. In step 308, in parallel with
depositing nanowires 1702a from first electrode pair 208a to first
region 1904a, nanowires 1702b can be deposited from second
electrode pair 208b to second region 1904b. In step 310, first and
second electrode pairs 208a and 208b can be removed from alignment
with their respective regions in parallel, by withdrawing print
head 3402 from destination surface 210.
[0165] Note that any number of electrode pairs may be formed on a
transfer surface to be used to transfer any number of corresponding
sets of nanowires in parallel, in a similar fashion to the
configuration of FIG. 34. By increasing the size of transfer
surface 206, to enable additional electrode pairs, increasing
numbers of simultaneous nanowire transfers may be performed in
parallel, increasing a rate of fabrication. The spacing of
electrodes 704 and 706 of electrode pairs on print heads may be
varied to associate and deposit different types of nanowires,
including different lengths, dopings, shell materials, etc.
Example Embodiments for Transferring Electrical Devices
[0166] Embodiments are described in this section for applying
electrical devices, such as integrated circuits, electrical
components, semiconductor die, optical devices, etc., to surfaces
in a similar manner as described above for nanowires. In
embodiments, one or more electrical devices are provided proximate
to an electrode pair on a transfer surface. The electrode pair is
energized such that an electrical device becomes associated with
the electrode pair. Subsequently, the electrical device is
deposited from the electrode pair to a destination surface.
[0167] FIG. 35 shows a flowchart 3500 providing example steps for
transferring electrical devices, according to example embodiments
of the present invention. For example, print head 702 of FIG. 7 can
be used to transfer electrical devices according to flowchart 3500.
For illustrative purposes, flowchart 3500 is described as follows
with respect to FIGS. 36-39, which show block diagrams of an
electrical device transfer system 3600, according to an embodiment
of the present invention. Other structural and operational
embodiments will be apparent to persons skilled in the relevant
art(s) based on the following discussion. Not all steps of
flowchart 3500 are necessarily performed in all embodiments.
[0168] Flowchart 3500 begins with step 3502. In step 3502, at least
one electrical device is provided proximate to an electrode pair.
For example, as shown in FIG. 36, electrical devices 3602 are
provided proximate to electrode pair 208. In FIG. 36, electrical
devices 3602 are present in solution 804, which flows in contact
with electrode pair 208, to enable electrical devices 3602 to be
positioned proximate to electrode pair 208. Alternatively,
electrical devices 3602 may be provided proximate to electrode pair
208 in other ways. In embodiments, electrical devices 3602 may all
be the same type of electrical device, or may include different
types.
[0169] In step 3504, an electric field is generated by electrodes
of the electrode pair to associate an electrical device with the
electrodes. For instance, an electrical potential may be coupled to
electrode pair 208 to generate the electric field. The electric
field generated by electrode pair 208 may be used to associate one
of electrical devices 3602 with electrode pair 208 that is
proximately located to electrode pair 208. As shown in FIG. 37,
electrical device 3602a is associated with electrode pair 208. In
an embodiment, associated electrical device 3602a is held suspended
at a distance from transfer surface 206 by the electric field.
[0170] The example embodiments described above for generating an
electric field by an electrode pair to associate nanostructures are
adaptable to associating electrical devices. For example, as
described with respect to FIG. 14, an electric field 1402 is
generated between electrodes 704 and 706 of electrode pair 208.
Electric field 1402 can be used to align electrical device
electrical device 3602a, and to position electrical device 3602a
between electrodes 704 and 706. When electrical device 3602a
encounters an AC electric field generated between electrodes 704
and 706, a field gradient results. A net dipole moment is produced
in proximate electrical devices 3602, and the AC field exerts a
torque on the dipole, such that proximate electrical device 3602a
aligns parallel to the direction of the electric field.
[0171] Furthermore, in an embodiment, the field gradient exerts a
dielectrophoretic force on proximate electrical device 3602a,
attracting it toward electrode pair 208, as described above for
nanowires with respect to FIG. 16. An electro-osmotic force may
also be generated, as described above, that opposes the
dielectrophoretic force attracting electrical device 3602a to the
electrodes. As these forces reach an equilibrium (or relative
equilibrium), electrical device 3602a is held in place such that it
becomes associated, or "pinned," with electrode pair 208.
[0172] As mentioned above, electrical devices 3602 in FIG. 36 may
all be the same type of electrical device or may include different
electrical device types. When different electrical device types are
present, electrodes 704 and 706 may be sized and/or positioned to
generate the electric field in a manner to only attract a
designated type of electrical device. In an embodiment, electrical
device 3602a may have a metal (or other material) patterned thereon
to enhance the attraction of electrical device 3602a to electrodes
208.
[0173] In step 3506, the electrode pair is aligned with a region of
the destination surface. For example, as shown in FIG. 38,
electrode pair 208 is aligned with destination surface 210, by
print head 702, which is moved towards destination surface 210. In
an embodiment, electrode pair 208 is aligned in contact with
destination surface 210. In another embodiment, electrode pair 208
is aligned adjacent to destination surface 210, a short distance
away from destination surface 210. Electrode pair 208 may be
aligned with any region of surface 210, including a generally open
region (i.e., no contacts on surface 210 are required), a region
having electrical contacts corresponding to electrode pair 208, or
other region. Electrode pair 208 is aligned with a region of
surface 210 on which electrical device 3602a is to be
positioned.
[0174] In step 3508, the electrical device is deposited from the
electrode pair to the region. Electrical device 3602a may be
deposited on destination surface 210 in a variety of ways. Various
example embodiments for depositing nanostructures on a surface are
described in detail above. For example, the embodiments described
above with respect to FIGS. 28-33 for depositing nanostructures may
be used to deposit electrical device 3602a. For example, in FIG.
28, a force 2802 is present (which may include one or more forces)
that attracted nanowires 1702 from print head 702 to destination
surface 210 and/or repelled nanowires 1702 from print head 702.
Force 2802 may also be used to deposit electrical device 3602a to
destination surface 210 from print head 702. Example forces that
may be present in force 2802 include an electric field (AC and/or
DC), a vacuum force, an electrostatic force, gravity, ultrasonic
excitation, and/or other forces. These and other passive and active
forces may be used to attract/repel electrical device 3602a, as
would be known to persons skilled in the relevant art(s).
Furthermore, ultrasonic vibration may be used, as described above
with respect to FIGS. 31A-31C, to aid in freeing electrical device
3602a from print head 702, to transfer to destination surface 210
(e.g., via a force such as gravity, an electrostatic force,
etc.).
[0175] In step 3510, the electrode pair is removed from alignment
with the region of the surface. For example, as shown in FIG. 39,
print head 702 is moved away from destination surface 210.
Electrical device 3602a remains deposited on surface 210. Print
head 702 can subsequently be used to repeat performing flowchart
3500 for the same region of surface 210, a different region of
surface 210, and/or a surface of a structure other than substrate
212, to deposit further electrical devices. Furthermore, in an
embodiment, print head 702 may be used to simultaneously transfer
nanostructures and electrical devices.
[0176] Using the techniques described herein, complex electrical
circuits can be formed, by using print heads to transfer
nanostructures and electrical devices to substrates.
Further Print Head Embodiments
[0177] Further embodiments are described in this section for
applying nanostructures to surfaces using print heads. Print heads
used to "print" nanowires onto a substrate in the presence of a
fluid, as described above, may cause a shear force that is
orthogonal to the motion of the print head as the print head
approaches the substrate. As a result, the fluid is forced out of
the region between the print head and the substrate due. This fluid
shear can displace the nanowires laterally, causing the nanowires
to be misplaced in the printing process.
[0178] For example, FIG. 40 shows a cross-sectional view of a
nanostructure transfer system 4000, according to an embodiment of
the present invention. As shown in FIG. 40, system 4000 includes
print head 702 and substrate 212. FIG. 41 shows a view of transfer
surface 206 of print head 702. Print head 702 is configured to
transfer nanostructures, such as a nanowire 1702 (shown end-on in
FIG. 40), from electrodes 704 and 706 to destination surface 210 in
a liquid solution 4004.
[0179] During the transfer process, print head 702 is moved towards
substrate 212 in the direction of arrow 4002, reducing a distance
between transfer surface 206 and destination surface 210. Arrows
4006 indicate directions of flow of solution 4004 as print head
4002 is moved towards substrate 212, as solution 4004 is forced out
of the region between transfer surface 206 and destination surface
210. Referring to FIG. 40, the relative lengths of arrows 4006
indicate a relative flow velocity at the locations of arrows 4006.
For instance, a flow velocity is lower for solution 4004 close to
one of transfer surface 206 and destination surface 210 relative to
solution 4004 midway between transfer surface 206 and destination
surface 210. Referring to FIG. 41, arrows 4006 indicate that
solution 4004 is forced outwardly in all directions from a central
region of transfer surface 2006.
[0180] As indicted in FIG. 41, solution 4004 is forced to flow
across nanowire 1702 when print head 702 is moved towards substrate
212. This fluid exerts a shear force on nanowire 1702, which may
undesirably displace nanowire 1702 laterally, causing nanowire 1702
to be misplaced in the printing process.
[0181] In embodiments, drain holes are formed in a print head to
remove fluid from the region between the print head and the
destination surface as the print head approaches the destination
surface. The drain holes reduce a shear force on the nanowires, to
enable the nanowires to be more reliably transferred from the print
head to the destination surface. For example FIG. 42 shows a
nanostructure transfer system 4200, according to an example
embodiment of the present invention. As shown in FIG. 42, system
4200 includes a print head 4202 and substrate 212. FIG. 43 shows a
view of transfer surface 206 of print head 4202. As shown in FIGS.
42 and 43, transfer surface 206 includes first and second openings
4204a and 4204b (also referred to as "drain holes"). First and
second openings 4204a and 4204b receive solution 4004 from the
region between transfer surface 206 and destination surface 210
when print head 4202 is moved toward substrate 210. Removal of
solution 4004 due to first and second openings 4204a and 4204b
reduces a shear force on nanowire 1702 while being deposited from
transfer surface 206 to destination surface 210.
[0182] FIG. 44 shows a flowchart 4400 for transferring
nanostructures to a destination surface, according to an example
embodiment of the present invention. System 4200 may perform
flowchart 4400, for example. Flowchart 4400 is described as
follows. Other structural and operational embodiments will be
apparent to persons skilled in the relevant art(s) based on the
following discussion.
[0183] In step 4402, a transfer surface of a print head is
positioned adjacent to a destination surface. For instance, as
shown in FIG. 42, transfer surface 206 of print head 4202 is
positioned adjacent to destination surface 210 of substrate
212.
[0184] In step 4404, a distance between the transfer surface and
the destination surface is reduced. Referring to FIG. 42, print
head 4202 is moved in the direction of arrow 4002 to reduce a
distance 4208 between transfer surface 206 and destination surface
210.
[0185] In step 4406, a fluid is received through at least one
opening in the transfer surface from between the transfer surface
and the destination surface during step 4404. As indicated by
arrows 4206 in FIGS. 42 and 43, solution 4004 between transfer
surface 206 and destination surface 210 flows outward from a
central region of transfer surface 2006 due to transfer surface 206
moving toward destination surface 210. Furthermore, as indicated by
arrows 4210 shown in FIG. 42, solution 4004 flows into openings
4204a and 4204b in transfer surface 206. Openings 4204a and 4204b
relieve at least a portion of the shear force received by nanowire
1702 by receiving solution 4004.
[0186] In step 4408, a nanowire associated with the transfer
surface is deposited to the destination surface. For instance, FIG.
45 shows a view of system 4200 of FIG. 42, where transfer surface
206 is proximate to destination surface 210, such that nanowire
1702 may be deposited to destination surface 210. Nanowire 1702 may
be deposited from transfer surface 206 to destination surface 210
in any manner described elsewhere herein, including as described
above with respect to flowchart 300 shown in FIG. 3. Subsequent to
the deposition of nanowire 1702, print head 4202 and substrate 212
may be moved apart.
[0187] Although two openings 4204 (openings 4204a and 4204b) are
shown in FIGS. 42 and 43, any number of openings 4204 may be
present in transfer surface 206. For example, instead of a pair of
openings 4204 (as shown in FIGS. 42 and 43), an array of openings
4204 of any number may be present at the locations of openings
4204a and 4204b. Such openings may have any shape, including being
round, rectangular, or any other shape.
[0188] Furthermore, openings 4204 may have any
distribution/geometry relative to electrodes 704 and 706 to further
reduce the shear force. For example, as shown in FIG. 43, openings
4204a and 4204b may be located relative to electrodes 704 and 706
so that nanowire 1702 is located midway between openings 4204a and
4204b. In this manner, a "dead zone" for flow of solution 4004 at
the location of nanowire 1702 is created (e.g., a flow stream is
parted at nanowire 1702), so that the shear force experienced by
nanowire 1702 may be brought close to none. In the embodiment of
FIG. 43, openings 4204 can be holes and/or slots that are
positioned symmetrically along either side of the long axis of
nanowire 1702.
[0189] Furthermore, as shown in FIG. 43, openings 4202 may have
lengths that are longer than a long axis length of nanowire 1702.
Alternatively, openings 4202 may have a length that is the same or
less than a long axis length of nanowire 1702. A width of openings
4204a and 4204b may be selected so that a substantial amount of
solution 4004 between openings 4204a and 4204b on either side of
nanowire 1702 may exit through openings 4204a and 4204b.
[0190] Although openings 4204 are shown in FIG. 42 as being located
along the length of nanowire 1702, alternatively or additionally,
openings 4204 may be located on transfer surface 206 adjacent to
one or both ends of nanowire 1702. Furthermore, although openings
4204a and 4204b are shown in FIG. 42 as penetrating all the way
through print head 4202, alternatively, openings 4204 may penetrate
partially through print head 4204 (e.g., may be recessed areas in
transfer surface 206, of any suitable depth).
[0191] In the example of FIGS. 42 and 43, solution 4004 is enabled
to passively flow into openings 4204. In another embodiment,
solution 4004 may be actively drawn into openings 4204. For
instance, a piston/cylinder arrangement, a corkscrew, vacuum
suction, and/or further mechanisms may be used to actively draw
solution 4004 into openings 4204. For example, FIG. 46 shows a
nanostructure transfer system 4600, according to an embodiment of
the present invention. System 4600 is generally similar to system
4200 shown in FIG. 42, with the addition of first and second
pistons 4602a and 4602b. Pistons 4602a and 4602b are located in
openings 4204a and 4204b, respectively. First piston 4602a and
opening 4204a form a first piston/cylinder arrangement, and second
piston 4602b and opening 4204b form a second piston/cylinder
arrangement. First and second pistons 4602a and 4602b may be
configured to move in the directions of arrows 4604 during step
4404 of flowchart 4400, to enable solution 4004 to be drawn into
openings 4204a and 4204b according to step 4406 of flowchart
4400.
Example Electrode Embodiments
[0192] Nanostructures and/or contaminants may become attached to
transfer surfaces of print heads, causing degradation in
performance. In embodiments, the transfer surface of nanostructure
print heads may be treated to prevent contaminants from sticking,
and/to increase a durability of the transfer surface. Such
embodiments may be particularly useful to extend a lifetime of a
print head/transfer surface when print heads/transfer surfaces are
expensive to replace. For example, a coating may be applied to the
transfer surface, such as a coating of a non-stick material. In an
embodiment, the coating may be removable. In this manner, the
coating may be removed and reapplied as needed when a coating wears
out, rather than having to dispose of the print head
completely.
[0193] For instance, FIG. 47 shows a cross-sectional view of a
print head 4700, according to an example embodiment of the present
invention. As shown in FIG. 47, a non-stick material layer 4702 is
formed on transfer surface 206 of print head 4700. Non-stick
material layer 4702 is a coating of a non-stick material that is
configured to reduce nanowire and contaminate adhesion. In
addition, non-stick material layer 4702 may be removed (e.g.,
stripped) from transfer surface 206, and reapplied to transfer
surface 206, to provide a longer lifespan to print head 4700.
[0194] Example advantages of non-stick material layer 4702 on
transfer surface 206 include preventing nanowire adhesion and
sticking, enabling the use of a higher nanowire capture voltage
(e.g., during step 304 of flowchart 300 in FIG. 3) so that
nanowires are not lost due to shear forces during the nanowire
transfer process (e.g., as described above with respect to FIGS. 41
and 42), enhancing nanowire transfer efficiency, and/or reducing
contamination and corrosion of print head 4700 to increase a
lifetime of print head 4700.
[0195] Non-stick material layer 4702 may be formed on transfer
surface 206 in any manner, including by coating transfer surface
206 from a solution (i.e., spin coating or dip coating) or by a
vapor phase deposition process. Non-stick material layer 4702 may
be configured to have weak adhesion properties, such as adhesion
properties characterized through van der Waals forces. Transfer
surface 206 may be treated with adhesion promoters to prevent
non-stick material layer 4702 from delaminating from transfer
surface 206. Example materials for non-stick material layer 4702
include materials that have very low van der Waals force attraction
with inorganic materials (contamination and nanowires), such as
organic molecules or fluorinated organics (e.g., Teflon). A
fluorinated organic material, such as Teflon, can have van der
Waals forces 3 orders of magnitude lower than a typical oxide
surface, thus making the strength of adhesion of contaminants to
transfer surface 206 relatively weak. A thickness and/or chemistry
of non-stick material layer 4702 may be selected as desired for the
particular application.
[0196] In addition, as described above, non-stick material layer
4702 may be removable. For instance, if nanowires and/or other
contamination does adhere to transfer surface 206 after one or more
uses, non-stick material layer 4702 may be removed using solvents,
plasma, thermal decomposition, or other removal material or
technique. After removal of non-stick material layer 4702, a fresh
replacement coating of non-stick material layer 4702 may be formed
on transfer surface 206. This replacement process is simpler and
less expensive than manufacturing a replacement print head 4700,
which may be relatively expensive.
[0197] For instance, another type of non-stick material that may be
applied to transfer surface 206, is a film of a material such as
SiO.sub.2 or Si.sub.3N.sub.4. Such a film may be deposited on
transfer surface 206 according to a plasma enhanced chemical vapor
deposition (PECVD) process or other process. Such a film may
prevent nanowires from sticking to transfer surface 206 by static
charge. Furthermore, such a film may be removed after use, and
reapplied to transfer surface 206, as needed, which may enable a
lifespan of transfer surface 206 to be increased.
Example Nanostructure Printing Processes and Systems
[0198] Example embodiments are described in this section for
nanostructure printing processes and systems. Embodiments are
described for fabricating devices that incorporate nanostructures.
These embodiments are provided for illustrative purposes, and are
not intended to be limiting.
[0199] For example, FIG. 48 shows a block diagram of a
nanostructure printing system 4800, according to an example
embodiment of the present invention. As shown in FIG. 48, system
4800 includes an association station 4802, an inspection station
4804, a printing station 4806, a cleaning station 4808, a panel
repair station 4812, and a panel drying station 4814. Association
station 4802, inspection station 4804, printing station 4806, and
cleaning station 4808 form a print head pipeline portion of system
4800, and printing station 4806, panel repair station 4812, and
panel drying station 4814 form a panel pipeline portion of system
4800.
[0200] System 4800 is described with respect to flowcharts 4900 and
5000 shown in FIGS. 49 and 50, respectively. Flowchart 4900 shows a
process for the print head pipeline portion of system 4800, and
flowchart 5000 shows a process for the panel pipeline of system
4800, according to example embodiments of the present invention.
For illustrative purposes, flowcharts 4900 and 5000 are described
as follows with respect to system 4800. Other structural and
operational embodiments will be apparent to persons skilled in the
relevant art(s) based on the following discussion. Not all elements
of system 4800 shown in FIG. 48 need be present in all embodiments,
and not all steps of flowcharts 4900 and 5000 are necessarily
performed in all embodiments.
[0201] Flowchart 4900 is first described. In step 4902 of flowchart
4900, nanostructures are associated with transfer surfaces of print
heads. For example, as shown in FIG. 48, association station 4802
receives a plurality of print heads 4818, including a print head
4810. Association station 4802 is configured to associate
nanostructures with a transfer surface of each print head of the
received plurality of print heads 4818. The association of
nanostructures with print heads 4818 may be performed in any manner
described elsewhere herein, such as described above with respect to
flowchart 300 in FIG. 3, or in other ways known to persons skilled
in the relevant art(s). As shown in FIG. 48, association station
4802 outputs a plurality of print heads and associated
nanostructures 4820.
[0202] For example, FIG. 51 illustrates nanostructures being
associated with transfer surfaces of print head 4810 in solution
(e.g., in a liquid environment) at association station 4802. In an
embodiment, print head 4810 is one of a plurality of print heads
received at association station 4802. In another embodiment, a
single print head 4810 is received. In the example of FIG. 51,
print head 4810 has six transfer surfaces 206a-206f. In other
embodiments, print head 4810 may have other numbers of transfer
surfaces 206, including a two-dimensional array of transfer
surfaces 206. Transfer surfaces 206a-206f are submerged in a
nanowire solution 5106 (e.g., a nanowire ink) contained by a
reservoir 5104. As shown in FIG. 51, print head 4810 has five
through-holes or openings 5108a-5108e, with each opening 5108 being
positioned between a corresponding adjacent pair of transfer
surfaces 206. Openings 5108 may be configured similarly to openings
4204 described above with respect to FIG. 42. In embodiments, print
head 4810 may include any number and configuration of openings
5108.
[0203] Although not shown in FIG. 51, in the current example, each
transfer surface 206a-206f includes a respective pair of electrodes
(e.g., electrode pair 208 of FIG. 2, which may include electrodes
704 and 706 shown in FIG. 7). The electrodes generate an electric
field (e.g., electric field 1402 shown in FIG. 14) to associate one
or more nanowires 5110 in nanowire solution 5106 with the
respective transfer surface 206. For example, FIG. 51 shows a first
nanowire 5110a in solution 5106 that is not associated with any of
transfer surfaces 206a-206b. A second nanowire 5110b is shown
associated with second transfer surface 206b. A third nanowire
5110c is nearby but not associated with first transfer surface
206a.
[0204] During or after step 4902, print head 4810 of FIG. 48 may
optionally be configured to flush excess nanostructures from
transfer surfaces 206 of plurality of print heads 4818 at
association station 4802. For example, FIG. 52 shows excess
nanowires being flushed from transfer surfaces 206a-206f of print
head 4810. In the example of FIG. 51, a fluid (e.g., solution 5106)
is shown being flowed through openings 5108a-5108e (as indicated by
arrows 5202) to flush excess nanowires 5110 from transfer surface
206a-206f. A fluid source (not shown in FIG. 52) configured to
produce a suitable fluid pressure may be coupled to an inlet 5102
of print head 4810, or may be otherwise coupled to print head 4810,
to provide the fluid to flow through openings 5108a-5108e. A fluid
velocity and flush time provided by the fluid source may be
determined for a particular application. For example, fluid
velocities in the range of 1-100 .mu.m/s may be used, during a
flush time of 60 minutes or less (e.g., 1 minute or less), in
embodiments.
[0205] Excess nanowires 5110, such as nanowire 5110c, which may be
desired to be flushed from transfer surfaces 206, are nanowires
that may be weakly associated with a transfer surface 206, that may
have become entangled with other nanowires 5110 that are
associated, and/or that may have become otherwise attached to (but
not associated with) a surface of print head 4810. For example,
nanowire 5110c is shown in FIG. 52 as having been flushed from
transfer surface 206a.
[0206] Referring back to flowchart 4900, in step 4904, an
inspection of the print heads is performed. For example, as shown
in FIG. 48, inspection station 4804 receives plurality of print
heads and associated nanostructures 4820. Inspection station 4804
is configured to perform an inspection of transfer surfaces 206 of
the received plurality of print heads, and to select at least one
print head of received plurality of print heads based on the
inspection. As shown in FIG. 48, inspection station 4804 outputs at
least one selected print head and associated nanostructures
4822.
[0207] For instance, FIG. 53 shows an example of inspection station
4804, according to an embodiment of the present invention. As shown
in FIG. 53, inspection station 4804 has received a plurality of
print heads 4810a-4810c. Each of print heads 4810a-4810c has a
respective plurality of transfer surfaces 206a-206f. An inspection
device 5302 is present that is configured to inspect arrangements
of nanowires 5110 associated with transfer surfaces 206 of print
heads 4810a-4810c. Inspection device 5302 may be an optical
inspection device (e.g., a microscope, a camera, and/or other
optical inspection device), an electrical inspection device, a
mechanical inspection device, and/or further type of inspection
device. Inspection device 5302 may be configured to determine
whether a sufficient number of nanostructures is present at each
transfer surface 206, to determine whether an unsuitable
arrangement of nanostructures is present at a transfer surface 206
(e.g., determine whether sufficient contact between electrodes is
made by the present nanostructures), and/or to otherwise determine
the suitability and/or unsuitability of an arrangement of
nanostructures at transfer surfaces 206 of print heads
4810a-4810c.
[0208] For example, in FIG. 53, inspection device 5302 may
determine that an insufficient number of nanowires 5110 (e.g., no
nanowires) is present at transfer surface 206c of print head 4810a,
while all transfer surfaces of print heads 4810b and 4810c have
sufficient numbers and arrangements of nanowires 5110. Because
inspection device 5302 determined that transfer surface 206c of
print head 4810 does not have a sufficient number of associated
nanowires 5110, print head 4810a may be indicated as having failed
inspection, while print heads 4810b and 4810c may be indicated as
having passed inspection.
[0209] In step 4906, one or more print heads are selected based on
the inspection. One or more print heads that passed inspection in
step 4904 may be selected. In the current example, because
inspection device 5302 determined that print heads 4810b and 4810c
passed inspection, while print head 4810a failed inspection, print
heads 4810b and 4810c may be selected for further processing in
system 4800. Note that in an embodiment, an arrangement of
nanowires 5110 at a print head 4810 that failed inspection may be
repaired. For example, in the current example, after transfer
surface 206c was determined (in step 4904) to be lacking a
sufficient number of nanowires, one or more additional nanowires
5110 may be associated with transfer surface 206c. Subsequently,
print head 4810a may be re-inspected (repeat step 4904). If print
head 4810a passes the re-inspection, print head 4810a may be
selected in step 4906. Example embodiments for repairing
arrangements of nanostructures on surfaces (e.g., transfer
surfaces, destination surfaces) are described in detail further
below.
[0210] In step 4908, the nanostructures are transferred from the
selected print head(s) to a destination surface. For example, as
shown in FIG. 48, printing station 4806 receives at least one
selected print head and associated nanostructures 4822. In the
current example, at least one selected print head and associated
nanostructures 4822 includes print heads 4810b and 4810c. Printing
station 4806 also receives a panel 4816, which is an example of
destination substrate 212 shown in FIG. 2. Printing station 4806 is
configured to transfer the nanostructures from the received at
least one of the plurality of print heads to a plurality of regions
of a surface of panel 4816. As shown in FIG. 48, printing station
4806 outputs a plurality of print heads 4824 and a panel with
deposited nanostructures 4828.
[0211] In embodiments, printing station 4806 may be configured to
transfer nanostructures from print heads 4810 to panel 4816 in any
manner described elsewhere herein, such as described above with
respect to flowchart 300 in FIG. 3, or in other ways known to
persons skilled in the relevant art(s). For instance, FIGS. 54-56
show views of printing station 4806 during a nanostructure transfer
process, according to an example embodiment of the present
invention. In an example embodiment, transfer surfaces 206 of print
heads 4802 and destination surface 210 may be coated with molecules
that interact via a lock and key mechanism. One of transfers
surfaces 206 or print heads 4802 may be coated with a first
molecule, and the other of transfer surfaces 206 or print heads
4802 may be coated with a second molecule. The first and second
molecules interact according to a molecular binding process that
occurs in biological systems. This type of molecular recognition
could be used to perform more sophisticated multi step depositions
of nanowires 5110. Such a molecular coating may be used on transfer
surfaces and destination surfaces in conjunction with other
nanostructure transfer embodiments described elsewhere herein.
[0212] FIG. 54 shows print head 4810b and panel 4816 in solution
5106. In FIG. 54, one or more nanowires 5110 are associated with
each of transfer surfaces 206a-206f of print head 4810b. In FIG.
55, print head 4810b is moved adjacent to panel 4816, so that each
of transfer surfaces 206a-206f is aligned with a corresponding one
of regions 1902a-1902f of panel 4816. In FIG. 56, print head 4810b
has deposited nanowires 5110 on panel 4816, and has withdrawn from
panel 4816. For instance, as shown in FIG. 56, nanowire 5110b is
deposited from transfer surface 206b to region 1904b of destination
surface 210 of panel 4816.
[0213] In step 4910, the print heads are cleaned. For example, as
shown in FIG. 48, cleaning station 4808 receives plurality of print
heads 4824. In the current example, plurality of print heads 4824
includes print heads 4810a-4810c. Cleaning station 4808 is
configured to clean the received plurality of print heads 4824.
Cleaning station 4808 may be configured to clean print heads 4824
in any manner, to remove any remaining nanostructures (e.g.,
nanostructures that were not deposited from a print head at
printing station 4806) and/or to remove any further
contaminants.
[0214] For instance, FIG. 57 shows an example of cleaning station
4808, according to an embodiment of the present invention. In FIG.
57, a fluid source 5702 may be present that outputs and/or directs
a fluid to transfer surfaces 206a-206f, as indicated by arrows
5704, to remove/dislodge contaminants from transfer surfaces
206a-206f. Fluid source 5702 may be any mechanism for providing a
fluid flow of a suitable pressure. The fluid output/directed by
fluid source 5702 may be solution 5106 and/or other fluid, such a
fluid configured to clean transfer surfaces 206a-206f.
[0215] As shown in FIG. 48, cleaning station 4808 outputs plurality
of print heads 4818. Plurality of print heads 4818 may be received
by association station 4802 for a next cycle of nanostructure
printing to be performed by system 4800. In an embodiment, a single
set of print heads may proceed from station to station in system
4800, such that at any particular time, all print heads are at the
same station. In another embodiment, at any particular time, each
station may be operating on a corresponding set of print heads,
which shift to a next station at predetermined time intervals.
[0216] Flowchart 5000, which relates to a pipeline of destination
panels, is now described. In step 5002 of flowchart 5000, the
nanostructures are received on the destination surface. For
example, as shown in FIGS. 54-56 and described above (with respect
to step 4908 of flowchart 4900), nanowires 5110 are transferred to
destination surface 210 of panel 4816.
[0217] In step 5004, the placement of received nanostructures on
the destination surface is repaired. Step 5004 is optional. For
example, as shown in FIG. 48, panel repair station 4812 receives
panel with deposited nanostructures 4828. Panel repair station 4812
is configured to perform an inspection of the nanostructures
transferred to the plurality of regions of the surface of the
received panel. For instance, FIGS. 58 and 59 show views of an
example panel repair station 4812, according to embodiments of the
present invention. In FIG. 58, an inspection device 5802 is present
that is configured to inspect arrangements of nanowires 5110 at
regions 1904 of panel 4816. Inspection device 5802 may be an
optical inspection device (e.g., a microscope, a camera, and/or
other optical inspection device), an electrical inspection device,
a mechanical inspection device, and/or further type of inspection
device. Inspection device 5802 may be configured to determine
whether a sufficient number of nanostructures is present at each
region 1904, to determine whether an unsuitable arrangement of
nanostructures is present at a region 1904 (e.g., sufficient
contact with electrical conductors on surface 210 is not made by
the present nanostructures), and/or to otherwise determine the
suitability and/or unsuitability of an arrangement of
nanostructures at regions 1904 of destination surface 210.
[0218] For example, in FIG. 58, inspection device 5802 may
determine that an insufficient number of nanowires 5110 (e.g., no
nanowires) is present at region 1904c of panel 4816. Because
inspection device 5802 determined that region 1904c does not have a
sufficient number of nanowires 5110, region 1904c may be indicated
for repair.
[0219] FIG. 59 shows a repair of the arrangement of nanostructures
at region 1904c being performed. In the example of FIG. 59, a print
head 5902 is shown repairing region 1904c, by depositing one or
more nanostructures, including a nanowire 5110c, on region 1904c.
Thus, in an embodiment, print head 5902 may be configured to add
one or more nanostructures to a region 1904 in need of repair.
Alternatively or additionally, if nanostructures are present in a
region 1904 in need of repair, print head 5902 may be configured to
rearrange the present nanostructures (e.g., move nanostructures
into contact with desired electrical conductors of the region
1904), and/or to remove one or more present nanostructures, to
create a sufficient nanostructure arrangement.
[0220] As shown in FIG. 48, panel repair station 4812 outputs a
panel with deposited nano structures 4830.
[0221] In step 5006, the destination surface is dried. For example,
as shown in FIG. 48, panel drying station 4814 receives panel with
deposited nanostructures 4830. Panel drying station 4814 is
configured to dry the deposited nanostructures on panel 4814. For
instance, FIG. 60 shows an example of panel drying station 4814,
according to an embodiment of the present invention. As shown in
FIG. 60, a dryer 6002 is present. Dryer 6002 is configured to dry
nanowires 5110 on panel 4814. Dryer 6002 may be configured to dry
nanowires 5110 on panel 4814 in any suitable manner, including by
radiating electromagnetic energy (e.g., infrared heat), by blowing
air 6004 (as shown in FIG. 60), and/or in any other manner.
[0222] As shown in FIG. 48, panel drying station 4814 outputs panel
4816 with deposited nanostructures 4826. Panel 4816 may receive
further processing, such as receiving a coating for environmental
protection of the deposited nanostructures. Panel 4816 with
nanostructures 4826 may be an electronic device, such as a display,
and/or may be incorporated into an electronic device. Examples of
such electronic devices are described further below.
[0223] Nanostructure printing system 4800 includes printing station
4806, which in the example of FIGS. 54-56, performs a "wet"
nanostructure transfer process (e.g., nanowires 5110 are
transferred in FIGS. 54-56 in reservoir 5104 containing solution
5106) (also referred to as "wet stamping"). In an alternative
embodiment, a nanostructure printing system may perform a "dry"
nanostructure transfer process. For example, FIG. 61 shows a
nanostructure printing system 6100, according to an example
embodiment of the present invention. Nanostructure printing system
6100 includes an association station 6102, a drying station 6104, a
print head repair station 6106, a printing station 6108, a cleaning
station 6110, and a panel repair station 6114. Printing station
6108 of system 6100 is configured to perform a dry nanostructure
transfer process. Association station 6102, drying station 6104,
print head repair station 6106, printing station 6108, and cleaning
station 6110 form a print head pipeline portion of system 6100, and
printing station 6108 and panel repair station 6114 form a panel
pipeline portion of system 6100.
[0224] System 6100 is described with respect to flowcharts 6200 and
6300 shown in FIGS. 62 and 63, respectively. Flowchart 6200 shows a
process for the print head pipeline portion of system 6100, and
flowchart 6300 shows a process for the panel pipeline of system
6100, according to example embodiments of the present invention.
For illustrative purposes, flowcharts 6200 and 6300 are described
as follows with respect to system 6100. Other structural and
operational embodiments will be apparent to persons skilled in the
relevant art(s) based on the following discussion. Not all elements
of system 6100 shown in FIG. 61 need be present in all embodiments,
and not all steps of flowcharts 6200 and 6300 are necessarily
performed in all embodiments.
[0225] Flowchart 6200 is first described. In step 6202 of flowchart
6200, nanostructures are associated with transfer surfaces of print
heads. For example, as shown in FIG. 61, association station 6102
receives a plurality of print heads 6118, including a print head
6112. Association station 6102 is configured to associate
nanostructures with a transfer surface of each print head the
received plurality of print heads 6118. The association of
nanostructures with print heads 6118 may be performed in any manner
described elsewhere herein, such as described above with respect to
flowchart 300 in FIG. 3, or in other ways known to persons skilled
in the relevant art(s). For instance, association station 6102 may
associate nanostructures with print heads in a similar manner as
described above for association station 4802 of FIG. 48. As shown
in FIG. 61, association station 6102 outputs a plurality of print
heads and associated nanostructures 6120.
[0226] In step 6204, the print heads are dried. For example, as
shown in FIG. 61, drying station 6104 receives plurality of print
heads and associated nanostructures 6120. Drying station 6104 is
configured to dry the transfer surfaces and associated
nanostructures of the received plurality of print heads. For
instance, drying station 6104 may include a dryer similar to dryer
6002 shown in FIG. 60, and described above, to perform drying. As
shown in FIG. 61, drying station 6104 outputs a dried plurality of
print heads and associated nanostructures 6122.
[0227] In step 6206, placement of nanostructures on one or more
print heads is repaired. Step 6206 is optional. For example, as
shown in FIG. 61, print head repair station 6106 receives dried
plurality of print heads and associated nanostructures 6122. Print
head repair station 6106 may be configured to inspect and repair
the nanostructures associated with the print heads in a similar
manner as panel repair station 4812 of FIG. 48, and described
above. For instance, print head repair station 6106 may include an
inspection device similar to inspection device 5802 shown in FIG.
58, to determine nanostructure arrangements on print heads in need
of repair. Furthermore, print head repair station 6106 may include
a print head or other repair device, such as print head 5902 shown
in FIG. 59, which may be used repair the determined nanostructure
arrangements in need of repair, in a wet or dry manner. As shown in
FIG. 61, panel repair station 6106 outputs a plurality of print
heads and associated nanostructures 6124.
[0228] In step 6208, the nanostructures are transferred from one or
more of the print heads to a destination surface. For example, as
shown in FIG. 61, printing station 6108 receives plurality of print
heads and associated nanostructures 6124. Printing station 6108
also receives a panel 6116, which is an example of destination
substrate 212 shown in FIG. 2. Printing station 6108 is configured
to transfer the nanostructures from the received plurality of print
heads to a plurality of regions of a surface of panel 6116.
Nanostructures may be transferred from all of the received print
heads, or from a selected portion of the print heads (e.g.,
selected in a similar manner as described above with respect to
step 4906 of flowchart 4900). In embodiments, printing station 6108
may be configured to transfer nanostructures to panel 6116
according to any dry transfer process described elsewhere herein,
such as described above with respect to flowchart 300 in FIG. 3, or
in other ways known to persons skilled in the relevant art(s). For
example, a difference in adhesion properties of the transfer
surface of the print head and of the destination surface may be
used to enable a transfer of nanostructures. The destination
surface may be configured to have greater adhesion (to the
nanostructures) than the transfer surface. In this manner, the
nanostructures associated with the transfer surface may be brought
into contact with the destination surface. As the transfer surface
is moved away from the destination surface, the greater adhesion of
the destination surface may cause the nanostructure to remain on
the destination surface.
[0229] In an embodiment, printing station 6108 may be configured
similarly to printing station 4806 shown in FIGS. 54-56, but
without the presence of reservoir 5104 and solution 5106. As shown
in FIG. 61, printing station 6108 outputs a plurality of print
heads 6126 and a panel with deposited nanostructures 6130.
[0230] In step 6210, the print heads are cleaned. For example, as
shown in FIG. 61, cleaning station 6110 receives plurality of print
heads 6126. Cleaning station 6110 is configured to clean the
received plurality of print heads 6126. Cleaning station 6110 may
be configured to clean print heads 6126 in any manner, to remove
any remaining nanostructures (e.g., nanostructures that were not
deposited from a print head at printing station 6108) and/or to
remove any further contaminants. For instance, cleaning station
6110 may be configured to clean print heads in a similar fashion as
cleaning station 4808 shown in FIG. 48. In an example embodiment,
cleaning station 6110 may include a fluid source, such as fluid
source 5702 shown in FIG. 57, to clean the transfer surfaces of
print heads 6126. As shown in FIG. 61, cleaning station 6110
outputs plurality of print heads 6118. Plurality of print heads
6118 may be received by association station 6102 for a next cycle
of nanostructure printing to be performed by system 6100. In an
embodiment, a single set of print heads may proceed from station to
station in system 6100, such that at any particular time, all print
heads are at the same station. In another embodiment, at any
particular time, each station may be operating on a corresponding
set of print heads, which shift forward to the next station at
predetermined time intervals.
[0231] Flowchart 6300, which relates to a pipeline of destination
panels for system 6100, is now described. In step 6302 of flowchart
6300, the nanostructures are received on the destination surface.
For example, as described above (with respect to step 6208 of
flowchart 6200), nanostructures are transferred to panel 6116 by
printing station 6108.
[0232] In step 6302, placement of the received nanostructures is
repaired on destination surface. Step 6302 is optional. For
example, as shown in FIG. 61, panel repair station 6114 receives
panel with deposited nanostructures 6130. Panel repair station 6114
is configured to perform an inspection of the nanostructures
transferred to the plurality of regions of the surface of the
received panel. For instance, panel repair station 6114 may be
configured similarly to panel repair station 4812 described above
with respect to FIG. 48, including being configured as shown in
FIGS. 58 and 59.
[0233] As shown in FIG. 61, panel repair station 6114 outputs panel
6116 with deposited nanostructures 6128. Panel 6116 may receive
further processing, such as receiving a coating for environmental
protection of nanostructures 6128. Panel 6116 with nanostructures
6128 may be an electronic device, such as a display, and/or may be
incorporated into an electronic device. Examples of such electronic
devices are described further below.
Example Captured Images of a Nanostructure Transfer Process
[0234] This section describes images captured during a
nanostructure transfer process performed according to an embodiment
of the present invention. FIG. 64 shows a nanostructure transfer
system 6400 used to perform the nanostructure transfer and to
capture the images of the transfer. As shown in FIG. 64, system
6400 includes print head 702, destination substrate 212, and an
image capturing microscope 6402. Transfer surface 206 of print head
702 includes first and second electrodes 704 and 706 and a
plurality of spacing members 2302. In FIG. 64, electrodes 704 and
706 hold an associated first nanowire 1702a (and a second nanowire
1702b, not visible in FIG. 64). First and second nanowires 1702a
and 1702b may have been associated with first and second electrodes
704 and 706 in any manner described elsewhere herein, such as
described above with respect to steps 302 and 304 of flowchart 300
(FIG. 3). FIG. 65 shows a first image 6500 captured by microscope
6402 of system 6400. First image 6500 shows first and second
nanowires 1702a and 1702b associated with first and second
electrodes 704 and 706 on transfer surface 206 of print head 702.
Note that in the current example, destination substrate 212 is
transparent to microscope 6402, and thus microscope 6402 may
capture images of nanowires 1702a and 1702b through substrate
212.
[0235] FIG. 66 shows another view of nanostructure transfer system
6400, where print head 702 is moved into contact with destination
substrate 212 (e.g., according to step 306 of flowchart 300 of FIG.
3). Spacing members 2302 on transfer surface 206 of print head 702
are in contact with destination surface 210 of substrate 212, to
maintain print head 702 at a predetermined distance (a height of
spacing members 2302) from substrate 212. FIG. 67 shows a second
image 6700 captured by microscope 6402 of first and second
nanowires 1702a and 1702b associated with first and second
electrodes 704 and 706, with print head 702 in contact with
destination surface 210 (as in FIG. 66).
[0236] FIG. 68 shows another view of nanostructure transfer system
6400. In FIG. 68, print head 702 remains in contact with
destination substrate 212 (as in FIG. 66). Furthermore, in FIG. 68,
nanowire 1702a (and nanowire 1702b, not visible in FIG. 68) is
transferred to destination surface 210 of substrate 212. Nanowires
1702a and 1702b may be transferred to destination surface 210 in
any manner described elsewhere herein, such as according to step
308 of flowchart 300 (FIG. 3) described above. For example, an
electric field generated by first and second electrodes 704 and 706
(e.g., step 304 of flowchart 300) may be removed to release first
and second nanowires 1702a and 1702b. Furthermore, destination
surface 210 may have been configured to have a charge that is
opposite to a charge of first and second nanowires 1702a and 1702b,
to attract nanowires 1702a and 1702b. FIG. 69 shows a third image
6900 captured by microscope 6402 of first and second nanowires
1702a and 1702b, where first and second nanowires 1702a and 1702b
are transferred to destination surface 210 (as in FIG. 68).
[0237] FIG. 70 shows another view of nanostructure transfer system
6400. In FIG. 70, print head 702 is moved away from destination
substrate 212 (e.g., according to step 310 of flowchart 300 in FIG.
3). Nanowire 1702a (and nanowire 1702b, not visible in FIG. 68)
remains deposited on destination surface 210 of substrate 212. FIG.
71 shows a fourth image 7100 captured by microscope 6402 of first
and second nanowires 1702a and 1702b, where first and second
nanowires 1702a and 1702b are on destination surface 210, and print
head 702 has been moved away from destination surface 210 (as in
FIG. 70). Note that in each of FIGS. 65, 67, 69, 71, microscope
6402 is focused on nanowires 1702a and 1702b. Thus, in FIG. 71,
first and second nanowires 1702a and 1702b remain in focus, while
focus is diminished with respect to transfer surface 206 of print
head 702 due to the increased separation between nanowires 1702a
and 1702b and transfer surface 206.
[0238] Example electronic devices and systems that can be formed
according to embodiments of the present invention are described
below.
Use of Nanowires and Electrical Devices Deposited According to the
Present Invention in Exemplary Devices and Applications
[0239] Numerous electronic devices and systems can incorporate
semiconductor or other type devices with thin films of nanowires
and/or electrical devices deposited according the methods of the
present invention. Some example applications for the present
invention are described below or elsewhere herein for illustrative
purposes, and are not limiting. The applications described herein
can include aligned or non-aligned thin films of nanowires, and can
include composite or non-composite thin films of nanowires.
[0240] Semiconductor devices (or other type devices) can be coupled
to signals of other electronic circuits, and/or can be integrated
with other electronic circuits. Semiconductor devices can be formed
on large substrates, which can be subsequently separated or diced
into smaller substrates. Furthermore, on large substrates (i.e.,
substrates substantially larger than conventional semiconductor
wafers), semiconductor devices formed thereon can be
interconnected.
[0241] The nanowires deposited by the processes and methods of the
present invention can also be incorporated in applications
requiring a single semiconductor device, and in multiple
semiconductor devices. For example, the nanowires deposited by the
processes and methods of the present invention are particularly
applicable to large area, macro electronic substrates on which a
plurality of semiconductor devices are formed. Such electronic
devices can include display driving circuits for active matrix
liquid crystal displays (LCDs), organic LED displays, field
emission displays. Other active displays can be formed from a
nanowire-polymer, quantum dots-polymer composite (the composite can
function both as the emitter and active driving matrix). The
nanowires deposited by the processes and methods of the present
invention are also applicable to smart libraries, credit cards,
large area array sensors, and radio-frequency identification (RFID)
tags, including smart cards, smart inventory tags, and the
like.
[0242] The nanowires deposited by the processes and methods of the
present invention are also applicable to digital and analog circuit
applications. In particular, the nanowires deposited by the
processes and methods of the present invention are useful in
applications that require ultra large-scale integration on a large
area substrate. For example, a thin film of nanowires deposited by
the processes and methods of the present invention can be
implemented in logic circuits, memory circuits, processors,
amplifiers, and other digital and analog circuits.
[0243] The nanowires deposited by the processes and methods of the
present invention can be applied to photovoltaic applications. In
such applications, a clear conducting substrate is used to enhance
the photovoltaic properties of the particular photovoltaic device.
For example, such a clear conducting substrate can be used as a
flexible, large-area replacement for indium tin oxide (ITO) or the
like. A substrate can be coated with a thin film of nanowires that
is formed to have a large bandgap, i.e., greater than visible light
so that it would be non-absorbing, but would be formed to have
either the HOMO or LUMO bands aligned with the active material of a
photovoltaic device that would be formed on top of it. Clear
conductors can be located on two sides of the absorbing
photovoltaic material to carry away current from the photovoltaic
device. Two different nanowire materials can be chosen, one having
the HOMO aligned with that of the photovoltaic material HOMO band,
and the other having the LUMO aligned with the LUMO band of the
photovoltaic material. The bandgaps of the two nanowires materials
can be chosen to be much larger than that of the photovoltaic
material. The nanowires, according to this embodiment, can be
lightly doped to decrease the resistance of the thin films of
nanowires, while permitting the substrate to remain mostly
non-absorbing.
[0244] Hence, a wide range of military and consumer goods can
incorporate the nanowires and electrical devices deposited by the
processes and methods of the present invention. For example, such
goods can include personal computers, workstations, servers,
networking devices, handheld electronic devices such as PDAs and
palm pilots, telephones (e.g., cellular and standard), radios,
televisions, electronic games and game systems, home security
systems, automobiles, aircraft, boats, other household and
commercial appliances, and the like.
[0245] Exemplary embodiments of the present invention have been
presented. The invention is not limited to these examples. These
examples are presented herein for purposes of illustration, and not
limitation. Alternatives (including equivalents, extensions,
variations, deviations, etc., of those described herein) will be
apparent to persons skilled in the relevant art(s) based on the
teachings contained herein. Such alternatives fall within the scope
and spirit of the invention.
[0246] All publications, patents and patent applications mentioned
in this specification are herein incorporated by reference to the
same extent as if each individual publication, patent or patent
application was specifically and individually indicated to be
incorporated by reference.
Example Embodiments
[0247] In an embodiment, a method for transferring nanowires to a
destination surface includes providing at least one nanowire
proximate to an electrode pair, generating an electric field with
electrodes of the electrode pair to associate the at least one
nanowire with the electrodes, aligning the electrode pair with a
region of the destination surface, and depositing the at least one
nanowire from the electrode pair to the region.
[0248] The transfer surface may be configured to have a first
electric charge.
[0249] The first electric charge may apply a repulsive
electrostatic force to the at least one nanowire, and the electric
field may be configured to attract the at least one nanowire to the
transfer surface against the repulsive electrostatic force.
[0250] The electric field may be biased with an alternating current
(AC) field to attract the at least one nanowire to the transfer
surface.
[0251] The electric field may be biased with a second AC field to
enable the at least one nanowire to move toward the destination
surface.
[0252] The destination surface may be configured to have a second
electric charge that is opposite the first electric charge.
[0253] The at least one nanowire may be enabled to be attracted to
the destination surface by an attractive electrostatic force of the
second electric charge by reducing a distance between the at least
one nanowire and the destination surface.
[0254] The at least one nanowire may be attracted toward the
destination surface with the second electric charge.
[0255] The transfer surface may be ultrasonically vibrated to
enable an attractive electrostatic force of the second electric
charge to attract the at least one nanowire toward the destination
surface.
[0256] Both the transfer surface and destination surface may be
ultrasonically vibrated.
[0257] The transfer surface and destination surface may be
ultrasonically vibrated synchronously.
[0258] A vacuum may be applied from the destination surface to the
transfer surface to move the at least one nanowire toward the
destination surface.
[0259] A second electric field associated with the destination
surface may be generated to attract the at least one nanowire
toward the destination surface.
[0260] Generation of the electric field may be ceased.
[0261] The destination surface may be configured to have a
hydrophilic property to attract a solution containing the at least
one nanowire toward the destination surface.
[0262] The transfer surface may be configured to have a hydrophobic
property to repel a solution containing the at least one
nanowire.
[0263] A solution containing the at least one nanowire may be
flowed on the electrode pair.
[0264] A rate of flow of the solution on the electrode pair may be
varied.
[0265] The electrode pair may include a first electrode and a
second electrode, and the at least one nanowire may include a first
nanowire. A first end of the first nanowire may be caused to be
positioned adjacent to a surface of the first electrode, and a
second end of the first nanowire may be caused to be positioned
adjacent to a surface of the second electrode.
[0266] The at least one nanowire may be caused to align
substantially in parallel with an axis through the first and second
electrodes.
[0267] The at least one nanowire may be positioned such that the
first and second ends are not in contact with the first and second
electrodes.
[0268] The region may include an electrical contact pair. The
electrode pair may be contacted with the electrical contact
pair.
[0269] The electrode pair may be contacted with the destination
surface.
[0270] A cantilever that mounts a first electrode of the electrode
pair may be caused to flex due to the contacting.
[0271] A pair of cantilevers that mount the electrode pair may be
caused to flex due to the contacting.
[0272] The electrode pair may be positioned adjacent to the
surface.
[0273] The electrode pair may be removed from alignment with the
region of the destination surface.
[0274] A second at least one nanowire may be provided proximate to
the electrode pair.
[0275] A second electric field may be generated with the electrodes
of the electrode pair to associate the second at least one nanowire
with the electrodes. The electrode pair may be aligned with a
second region of the surface. The at least one nanowire may be
deposited from the electrode pair to the second region.
[0276] The first electrode pair and a second electrode pair may be
on a common transfer surface. In parallel with the providing the
first at least one nanowire proximate to the first electrode pair,
a second at least one nanowire proximate may be provided to the
second electrode pair. In parallel with the generating the first
electric field, a second electric field may be generated with
second electrodes of the second electrode pair to associate the
second at least one nanowire with the second electrodes. In
parallel with the aligning the first electrode pair with the first
region of the surface, the second electrode pair may be aligned
with a second region of the surface. In parallel with the
depositing the first at least one nanowire from the first electrode
pair to the first region, the second at least one nanowire may be
deposited from the second electrode pair to the second region.
[0277] Uncoupled nanowires may be removed from the electrode
pair.
[0278] In another embodiment, a system for transferring nanowires
to a destination may include a body having a transfer surface, an
electrode pair on the transfer surface, a suspension that includes
a plurality of nanowires provided proximate to the electrode pair,
a signal generator coupled to the electrode pair, wherein the
signal generator is configured to enable electrodes of the
electrode pair to generate an electric field to associate at least
one nanowire of the plurality of nanowires with the electrodes, and
an alignment mechanism configured to align the electrode pair with
a region of the destination surface to enable the associated at
least one nanowire to be deposited from the electrode pair to the
region.
[0279] The transfer surface may have a first electric charge.
[0280] The first electric charge may apply a repulsive
electrostatic force to the at least one nanowire, and the electric
field may attract the at least one nanowire to the transfer surface
against the repulsive electrostatic force.
[0281] The signal generator may bias the electric field with an
alternating current (AC) field to attract the at least one nanowire
to the transfer surface.
[0282] The signal generator may bias the electric field with a
second AC field to enable the associated at least one nanowire to
move toward the destination surface.
[0283] The destination surface may have a second electric charge
that is opposite the first electric charge.
[0284] The alignment mechanism may be configured to reduce a
distance between the at least one nanowire and the destination
surface to enable the associated at least one nanowire to be
attracted to the destination surface by an attractive electrostatic
force of the second electric charge.
[0285] The associated at least one nanowire may be attracted toward
the destination surface by the second electric charge.
[0286] The system may further include an ultrasonic vibration
source configured to vibrate the transfer surface to enable an
attractive electrostatic force of the second electric charge to
attract the associated at least one nanowire toward the destination
surface.
[0287] The ultrasonic vibration source may be configured to vibrate
both the transfer surface and destination surface.
[0288] The ultrasonic vibration source may be configured to vibrate
the transfer surface and destination surface synchronously.
[0289] The system may further include a vacuum source configured to
apply a vacuum from the destination surface to the transfer surface
to move the associated at least one nanowire toward the destination
surface.
[0290] The system may further include an electric field source
configured to generate a second electric field associated with the
destination surface to attract the associated at least one nanowire
toward the destination surface.
[0291] The signal generator may be configured to reduce an
intensity of the electric field to enable the associated at least
one nanowire to be attracted toward the destination surface.
[0292] The destination surface may be configured to have a
hydrophilic property to attract a fluid containing the associated
at least one nanowire toward the destination surface.
[0293] The transfer surface may be configured to have a hydrophobic
property to repel the fluid containing the associated at least one
nanowire.
[0294] The system may further include a container that contains the
suspension and the electrode pair.
[0295] The suspension may be flowed over the electrode pair.
[0296] The electrode pair may include a first electrode and a
second electrode, and the at least one nanowire may include a first
nanowire. The electric field may cause a first end of the first
nanowire to be positioned adjacent to a surface of the first
electrode, and a second end of the first nanowire to be positioned
adjacent to a surface of the second electrode.
[0297] The electric field may align the at least one nanowire
substantially in parallel with an axis through the first and second
electrodes.
[0298] The electric field may position the at least one nanowire
such that the first and second ends are not in contact with the
first and second electrodes.
[0299] The region may include an electrical contact pair. The
alignment mechanism may be configured to contact the electrode pair
with the electrical contact pair.
[0300] The alignment mechanism may be configured contact the
electrode pair with the destination surface.
[0301] The transfer surface may have a cantilever that mounts a
first electrode of the electrode pair. The cantilever is configured
to flex if the electrode pair contacts the destination surface.
[0302] The transfer surface may have a pair of cantilevers that
mount first and second electrodes of the electrode pair. The pair
of cantilevers is configured to flex if the electrode pair contacts
the destination surface.
[0303] The alignment mechanism may be configured to position the
electrode pair adjacent to the surface.
[0304] The system may further include a plurality of spacers on the
transfer surface.
[0305] The alignment mechanism may be configured to remove the
electrode pair from alignment with the region of the destination
surface after the associated at least one nanowire is
deposited.
[0306] A second electrode pair may be on the transfer surface.
[0307] In another embodiment, a method for applying nanowires to a
destination surface may include aligning an electrode pair having
an associated at least one nanowire with a region of the
destination surface, and depositing the at least one nanowire from
the electrode pair to the region.
[0308] In another embodiment, a system for transferring electrical
devices to a destination surface may include a body having a
transfer surface, an electrode pair on the transfer surface, a
suspension that includes a plurality of electrical devices provided
proximate to the electrode pair, a signal generator coupled to the
electrode pair, wherein the signal generator is configured to
enable electrodes of the electrode pair to generate an electric
field to associate an electrical device of the plurality of
electrical devices with the electrodes, and an alignment mechanism
configured to align the electrode pair with a region of the
destination surface to enable the associated electrical device to
be deposited from the electrode pair to the region.
[0309] The system may further include an ultrasonic vibration
source configured to vibrate the transfer surface to enable an
attractive electrostatic force to attract the associated electrical
device toward the destination surface.
[0310] The ultrasonic vibration source may be configured to vibrate
both the transfer surface and destination surface.
[0311] The ultrasonic vibration source may be configured to vibrate
the transfer surface and destination surface synchronously.
[0312] The system may further include an ultrasonic vibration
source configured to vibrate the transfer surface to enable an
attractive electrostatic force to attract the associated electrical
device toward the destination surface.
[0313] The ultrasonic vibration source may be configured to vibrate
both the transfer surface and destination surface.
[0314] The ultrasonic vibration source may be configured to vibrate
the transfer surface and destination surface synchronously.
[0315] In another embodiment, a method for transferring nanowires
to a destination surface may include positioning a transfer surface
of a print head adjacent to a destination surface, wherein a
nanowire is associated with the transfer surface, reducing a
distance between the transfer surface and the destination surface,
receiving a fluid in at least one opening in the transfer surface
from between the transfer surface and the destination surface
during the reducing, and depositing the nanowire from the transfer
surface to the destination surface.
[0316] The fluid may be received in first and second openings in
the transfer surface, the nanowire being associated with the
transfer surface at a location substantially midway between the
first and second openings.
[0317] The first and second openings may each have a length that is
greater than a length of a long axis of the nanowire.
[0318] The lengths of the first and second openings may be
positioned in the transfer surface in parallel with the long axis
of the nanowire.
[0319] A piston may be moved within each of the first and second
openings to draw the fluid from between the transfer surface and
the destination surface into the first and second openings.
[0320] In another embodiment, a system for transferring nanowires
to a destination surface may include a body having a transfer
surface, at least one opening in the transfer surface, and an
electrode pair formed on the transfer surface. The electrode pair
may be configured to generate an electric field to associate a
nanowire with the electrode pair. The at least one opening may be
configured to receive a fluid from between the transfer surface and
the destination surface.
[0321] The at least one opening may be configured to receive the
fluid from between the transfer surface and the destination surface
when the transfer surface is being moved toward the destination
surface.
[0322] The at least one opening may include a first opening and a
second opening. The electrode pair may be configured to associate
the nanowire with the transfer surface at a location substantially
midway between the first and second openings.
[0323] The first and second openings may each have a length that is
greater than a length of a long axis of the nanowire.
[0324] The first and second openings may be positioned in the
transfer surface such that the lengths of the first and second
openings are configured to be parallel with the long axis of the
nanowire.
[0325] The system may further include a first piston in the first
opening and a second piston in the second opening. The first and
second pistons may be configured to draw the fluid from between the
transfer surface and the destination surface into the first and
second openings.
[0326] In another embodiment, a method for transferring nanowires
to a destination substrate may include associating nanostructures
with transfer surfaces of a plurality of print heads, performing an
inspection of the transfer surfaces of the plurality of print
heads, selecting at least one print head of the plurality of print
heads based on the inspection, and transferring the nanostructures
from the selected at least one print head to a plurality of regions
of a surface of a destination substrate.
[0327] Excess nanostructures may be flushed from the transfer
surfaces of the plurality of print heads.
[0328] The selected at least one print head may be cleaned after
the transferring.
[0329] An inspection may be performed of the nanostructures
transferred to the plurality of regions of the surface of the
destination substrate.
[0330] An arrangement of nanostructures transferred to a region of
the surface of the destination substrate in need of repair may be
determined, and the determined arrangement of nanostructures may be
repaired.
[0331] The transfer surfaces may be positioned in a suspension
containing a plurality of nanostructures, and an electric field may
be generated with electrodes of an electrode pair of each transfer
surface to associate nanostructures with the electrode pair of each
transfer surface.
[0332] The associated nanostructures may be deposited from at least
one electrode pair of the selected at least one print head to the
surface of the destination substrate.
[0333] In another embodiment, a method for transferring nanowires
to a destination substrate may include associating nanostructures
with transfer surfaces of a plurality of print heads, drying the
transfer surfaces having associated nanostructures, performing an
inspection of the dried transfer surfaces having associated
nanostructures, and transferring the nanostructures from the dried
transfer surfaces to a plurality of regions of a surface of the
destination substrate.
[0334] An arrangement of nanostructures associated with a transfer
surface of a print head in need of repair may be determined, and
the determined arrangement of nanostructures may be repaired.
[0335] Excess nanostructures may be flushed from the transfer
surfaces of the plurality of print heads prior to the drying.
[0336] The plurality of print heads may be cleaned after the
transferring.
[0337] An inspection of the nanostructures transferred to the
plurality of regions of the surface of the destination substrate
may be performed.
[0338] An arrangement of nanostructures transferred to a region of
the surface of the destination substrate in need of repair may be
determined, and the determined arrangement of nanostructures may be
repaired.
[0339] The transfer surfaces may be positioned in a suspension
containing a plurality of nanostructures, and an electric field may
be generated with electrodes of an electrode pair of each transfer
surface to associate nanostructures with the electrode pair of each
transfer surface.
[0340] The associated nanostructures may be deposited from at least
one electrode pair of the selected at least one print head to the
surface of the destination substrate.
[0341] In another embodiment, a system for transferring nanowires
to a destination substrate may include an association station
configured to receive a plurality of print heads, and to associate
nanostructures with a transfer surface of each of the received
plurality of print heads, a printing station configured to receive
a destination substrate and at least one of the plurality of print
heads, and to transfer the nanostructures from the received at
least one of the plurality of print heads to a plurality of regions
of a surface of the destination substrate, and a cleaning station
configured to receive the plurality of print heads from the
printing station, and to clean the received plurality of print
heads.
[0342] The association station may be configured to flush excess
nanostructures from the transfer surfaces of the plurality of print
heads.
[0343] The system may further include a repair station configured
to receive the destination substrate, and to perform an inspection
of the nanostructures transferred to the plurality of regions of
the surface of the destination substrate.
[0344] The repair station may be configured to determine an
arrangement of nanostructures transferred to a region of the
surface of the destination substrate in need of repair based on the
inspection, and to repair the determined arrangement of nano
structures.
[0345] The printing station may be configured to perform a wet
transfer of the nano structures.
[0346] The system may further include an inspection station
configured to receive the plurality of print heads from the
association station, to perform an inspection of the transfer
surfaces of the plurality of print heads, and to select at least
one print head of the plurality of print heads based on the
inspection. The printing station may be configured to transfer the
nanostructures from the selected at least one print head to the
plurality of regions of the surface of the destination
substrate.
[0347] The system may further include a panel drying station
configured to receive the destination substrate, and to dry the
nanostructures transferred to the plurality of regions of the
surface of the destination substrate.
[0348] The printing station may be configured to perform a dry
transfer of the nano structures.
[0349] The system may further include a print head drying station
configured to receive the plurality of print heads, and to dry the
transfer surfaces and the nanostructures associated with the
transfer surfaces of the plurality of print heads.
[0350] The system may further include a repair station configured
to perform an inspection of the dried transfer surfaces having
associated nanostructures, to determine an arrangement of
nanostructures associated with a transfer surface of a print head
in need of repair based on the inspection, and to repair the
determined arrangement of nano structures.
* * * * *