U.S. patent application number 12/898416 was filed with the patent office on 2011-04-07 for patterning of solid state features by direct write nanolithographic printing.
This patent application is currently assigned to Northwestern University. Invention is credited to Vinayak P. Dravid, Xiaogang Liu, Chad A. Mirkin, Ming Su.
Application Number | 20110081526 12/898416 |
Document ID | / |
Family ID | 23338292 |
Filed Date | 2011-04-07 |
United States Patent
Application |
20110081526 |
Kind Code |
A1 |
Mirkin; Chad A. ; et
al. |
April 7, 2011 |
PATTERNING OF SOLID STATE FEATURES BY DIRECT WRITE NANOLITHOGRAPHIC
PRINTING
Abstract
The present invention includes a method of fabricating
organic/inorganic composite nanostructures on a substrate
comprising depositing a solution having a block copolymer and an
inorganic precursor on the substrate using dip pen nanolithography.
The nanostructures comprises arrays of lines and/or dots having
widths/diameters less than 1 micron. The present invention also
includes a device comprising an organic/inorganic composite
nanoscale region chemically bonded to a substrate, wherein the
nanoscale region, wherein the nanoscale region has a nanometer
scale dimension other than height.
Inventors: |
Mirkin; Chad A.; (Wilmette,
IL) ; Dravid; Vinayak P.; (Glenview, IL) ; Su;
Ming; (Evanston, IL) ; Liu; Xiaogang;
(Evanston, IL) |
Assignee: |
Northwestern University
|
Family ID: |
23338292 |
Appl. No.: |
12/898416 |
Filed: |
October 5, 2010 |
Related U.S. Patent Documents
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Application
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Filing Date |
Patent Number |
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11847263 |
Aug 29, 2007 |
7811635 |
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12898416 |
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10320721 |
Dec 17, 2002 |
7273636 |
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11847263 |
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60341614 |
Dec 17, 2001 |
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Current U.S.
Class: |
428/195.1 ;
427/256; 977/855; 977/857 |
Current CPC
Class: |
B82B 3/00 20130101; B82Y
10/00 20130101; B82Y 30/00 20130101; G03F 7/0002 20130101; Y10S
977/855 20130101; Y10T 428/24926 20150115; Y10S 977/857 20130101;
B82Y 40/00 20130101; Y10T 428/24802 20150115; Y10T 428/265
20150115 |
Class at
Publication: |
428/195.1 ;
427/256; 977/855; 977/857 |
International
Class: |
B32B 3/10 20060101
B32B003/10; B05D 5/12 20060101 B05D005/12 |
Goverment Interests
[0002] This invention was made with governmental support under
grant ______. The government has certain rights in the invention.
Claims
1-39. (canceled)
40. A method of nanolithography comprising patterning a nanoscopic
deposit comprising a solid state material precursor on a substrate,
and converting the solid state material precursor to the solid
state material.
41. The method according to claim 40, wherein the solid state
material is an oxide.
42. (canceled)
43. The method according to claim 40, wherein the solid state
material is mesoporous.
44-45. (canceled)
46. The method according to claim 40, wherein the nanoscopic
deposit has at least one dimension which is less than about 200
nm.
47. The method according to claim 40, wherein the converting is
carried out by heating.
48-49. (canceled)
50. The method according to claim 40, wherein the solid state
material precursor is a sol.
51. The method according to claim 50, wherein the nanoscopic
deposit is a dot.
52-53. (canceled)
54. The method according to claim 50, wherein the substrate is
silicon or silicon oxide.
55. A method of fabricating inorganic/organic nanostructures
comprising depositing an ink on a substrate by direct write
nanolithography to form a deposit, wherein the ink comprises an
inorganic precursor and at least one organic polymer.
56. (canceled)
57. The method according to claim 55, wherein the inorganic
precursor is a metal oxide precursor.
58. The method according to claim 55, wherein the organic polymer
is an amphiphilic polymer.
59. The method according to claim 55, wherein the deposit is
heated.
60. The method according to claim 55, wherein the deposit has at
least one lateral dimension of about 1,000 nm or less.
61-69. (canceled)
70. A nanoscopically patterned substrate comprising on the
substrate surface at least one deposit prepared by the method
according to claim 40.
71-87. (canceled)
88. A device comprising: a substrate, at least one nanostructure on
the substrate prepared by direct-write nanolithographic printing,
the nanostructure having at least one lateral dimension of about
1,000 nm or less and comprising metal oxide precursor or metal
oxide.
89-90. (canceled)
91. The device according to claim 88, wherein the nanostructure
comprises an organic/inorganic composite.
92. (canceled)
93. The device according to claim 88, wherein the nanostructure
comprises a sol-gel structure.
94-98. (canceled)
99. The device according to claim 88, wherein the lateral dimension
is about 500 nm or less.
100-102. (canceled)
103. The device according to claim 88, wherein the nanostructure
comprises a catalyst for the growth of larger structures.
104. The device according to claim 88, wherein the nanostructure
comprises a wave guide material.
105-142. (canceled)
Description
CROSS-REFERENCE TO RELATED PATENT APPLICATIONS
[0001] This application claims benefit of provisional application
60/341,614, filed Dec. 17, 2001, the complete disclosure of which
is incorporated herein by reference in its entirety.
BACKGROUND OF THE INVENTION
[0003] DIP-PEN NANOLITHOGRAPHY.TM. printing (DPN.TM. printing) is a
high resolution direct patterning technique in which an "ink" is
transferred to a substrate using conventional nanoscopic tips
including, for example, scanning probe microscopic (SPM) and atomic
force microscopic (AFM) tips. See, e.g., U.S. patent application
Ser. Nos. 60/115,133, filed Jan. 7, 1999; 60/157,633, filed Oct. 4,
1999; 09/477,997, filed Jan. 5, 2000; 60/207,711, filed May 26,
2000; 60/207,713, filed May 26, 2000; 09/866,533, filed May 24,
2001; and 60/326,767, filed Oct. 2, 2001, and PCT applications
numbers PCT/US00/00319, filed Jan. 7, 2000 (publication number WO
00/41213), and PCT/US01/17067, filed May 25, 2001, the complete
disclosures of which are incorporated herein by reference.
[0004] DIP-PEN NANOLITHOGRAPHY.TM. printing and DPN.TM. are
trademarks of NanoInk, Inc., Chicago, Ill. DPN-related products
including hardware, software, instrumentation, and kits can be
obtained from NanoInk.
[0005] The development of dip pen nanolithographic printing is
described in patent application Ser. No. 09/866,533, filed May 24,
2001, particularly in the "Background of the Invention" section
(pages 1-3), which is hereby incorporated by reference in its
entirety.
[0006] DPN printing can be used for many ink-substrate combinations
including, for example, alkylthiol and arylthiol self-assembly on
gold (reference 1) and has also been extended to silazanes on
semiconductor surfaces (reference 3) and metal structures on
conductive surfaces (reference 4). In addition, it has been used
extensively as a way of making patterns out of simple organic and
complex biological molecules, including thiol-functionalized
proteins and alkylthiol-modified oligonucleotides, which can be
used to direct the assembly of higher-ordered architectures
(reference 5).
[0007] Solid state microscale structures are important to industry
including the electronics and optical communications industries. To
increase the speed and device density of integrated circuits, it is
important to make structures even smaller than currently possible.
It is an important commercial goal of nanotechnology to manufacture
solid state structures on a nanoscale.
[0008] A variety of patterning techniques have been used in
attempts to fabricate nanoscale structures including
photolithography, X-ray lithography, and electron beam lithography.
However, attempted miniaturization in making electronic and optical
devices can generate significant problems. For example, failure to
provide adequate separation between electrical current carrying
features may lead to short circuiting. Additionally, both optical
and electrical features must be well defined and be dimensionally
accurate to ensure that the devices operate as designed.
[0009] The prior art lithographic methods for making nanoscale
solid state features are generally limited to scales larger than
nanoscopic. Therefore, it would be advantageous to have a process
which has the nanoscale precision and capability of DPN printing
and the ability to form glass and ceramic structures. Preferably,
the process should include a suitable reactive process such as, for
example, sol-gel processes. Sol-gel chemistry is a useful
industrial method for making inorganic components including the
formation of metal oxides from metal oxide precursors.
SUMMARY OF THE INVENTION
[0010] In this section, the invention is summarized, although this
summary should not limit the invention which is described in detail
and claimed below.
[0011] In one embodiment, the present invention provides a method
of nanolithography comprising: providing a substrate, providing a
nanoscopic tip having an inking composition thereon, wherein the
inking composition comprises at least one metal oxide precursor;
transferring the inking composition from the nanoscopic tip to the
substrate to form a deposit on the substrate comprising at least
one metal oxide precursor.
[0012] In addition, the present invention also provides a method of
nanolithography comprising: positioning a scanning probe
microscopic tip having a reactive ink composition thereon relative
to a substrate so that the reactive ink composition is transferred
from the nanoscopic tip to the substrate to form a deposit on the
substrate, wherein the reactive ink is a sol-gel precursor capable
of undergoing a sol-gel reaction.
[0013] In another embodiment, the invention provides a method of
nanolithography comprising patterning a nanoscopic deposit
comprising a solid state material precursor on a substrate, and
converting the solid state material precursor to the solid state
material.
[0014] Still further, the invention provides in another embodiment
a method of fabricating inorganic/organic nanostructures comprising
depositing an ink on a substrate by direct write nanolithography to
form a deposit, wherein the ink comprises an inorganic precursor
and at least one organic polymer.
[0015] The invention also includes nanoscopically patterned
substrates comprising on the substrate surface at least one deposit
prepared by the methods described herein.
[0016] The invention, in addition, also provides a device
comprising: a substrate, at least one nanostructure on the
substrate prepared by direct write nanolithography, the
nanostructure having at least one lateral dimension of about 1,000
nm or less and comprising metal oxide precursor or metal oxide.
[0017] The invention also provides a device comprising: a
substrate, at least one nanoscale feature on the substrate prepared
by direct-write nanolithography, the nanoscale feature having at
least one lateral dimension of about 1,000 nm or less and
comprising a sol-gel material.
[0018] The invention also provides a nanoarray comprising a
plurality of nanostructures on a substrate prepared by direct-write
nanolithography, the nanostructures having at least one lateral
dimension of about 1,000 nm or less and comprising at least one
metal oxide precursor or one metal oxide.
[0019] Basic and novel features of the invention are set forth
below and include, for example, direct write capability, serial
patterning with ultrahigh resolution, molecular generality and use
of wide variety of functional groups and materials, relatively low
cost, ease of use, non-planar substrates, and unparalleled
registration. The invention, briefly, opens up the opportunity for
using DPN printing to deposit solid-state materials rather than
organic molecules onto surfaces with the resolution of an AFM
without the need for a driving force other than chemisorption such
as, for example, applied fields. The invention can be used in areas
ranging from mask fabrication to the evaluation of solid-state
nanoelectronic structures and devices fabricated by DPN printing.
Because the diffusion coefficients of sol inks are qualitatively
comparable to that of alkanethiols on gold, relatively fast
patterning by DPN printing can be carried out. The composite
nanostructures described herein can have large surface areas that
are important for catalyst and wave-guide applications. Use of
complicated and expensive resists, photomasks, and molds are not
needed.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020] FIG. 1. Schematic diagram illustrating deposition of metal
oxide precursors and metal oxides on a substrate surface from an
AFM tip.
[0021] FIG. 2. (A) Topographic AFM image of composite tin
oxide/P-123 nanostructures on silicon oxide; the writing speed for
each line is 0.2 .mu.m/sec. (B) Lateral force microscope (LFM)
image of a dot array of aluminum oxide/P-123 composite
nanostructures formed on silicon; the holding time for each dot is
1 second. AFM images collected before (C) and after (D) heating
silicon oxide/P-123 composite nanostructures in air at 400.degree.
C. for 2 hours; the writing speed is 0.1 .mu.m/sec. Note the
lateral dimensions are enlarged due to tip convolution.
[0022] FIG. 3. (A) Scanning Electron Microscope (SEM) image of a 4
.mu.m SnO.sub.2 dot formed by holding an ink-coated tip on the
substrate for 30 seconds. (B) EDX analysis of the SnO.sub.2 dot.
(C) EDX of the SiO.sub.2 substrate outside of the dot. (D) TEM
image of the mesoporous SiO.sub.2. The image was collected from
heated samples with a Hitachi HF-2000 TEM.
DETAILED DESCRIPTION OF THE INVENTION
[0023] Nanolithography, including DPN printing, can be used to
practice the present invention. For example, in patent application
Ser. No. 09/866,533, filed May 24, 2001, (U.S. patent publication
no. US 2002/0063212 A1 published May 30, 2002 to Mirkin et al.) DPN
printing background and procedures are described in detail covering
a wide variety of embodiments including, for example: [0024]
background (pages 1-3); [0025] summary (pages 3-4); [0026] brief
description of drawings (pages 4-10); [0027] use of scanning probe
microscope tips (pages 10-12); [0028] substrates (pages 12-13);
[0029] patterning compounds (pages 13-17); [0030] practicing
methods including, for example, coating tips (pages 18-20); [0031]
instrumentation including nanoplotters (pages 20-24); [0032] use of
multiple layers and related printing and lithographic methods
(pages 24-26); [0033] resolution (pages 26-27); [0034] arrays and
combinatorial arrays (pages 27-30); [0035] software and calibration
(pages 30-35; 68-70); [0036] kits and other articles including tips
coated with hydrophobic compounds (pages 35-37); [0037] working
examples (pages 38-67); [0038] corresponding claims and abstract
(pages 71-82); and [0039] FIGS. 1-28.
[0040] All of the above document text, including each of the
various subsections enumerated above including the figures, is
hereby incorporated by reference in its entirety and form part of
the present disclosure, supporting the claims.
[0041] Additional nanolithographic methods, including dip pen and
aperture pen nanolithography, are also disclosed in U.S. Patent
Publication No. 20020122873 A1 published Sep. 5, 2002 to Mirkin et
al., which is also hereby incorporated by reference in its entirety
and form part of the present disclosure, supporting the claims.
[0042] In addition, the development of patterning of solid state
structures is described, with literature citations, in priority
application 60/341,614, filed Dec. 17, 2001, including the use of
dip pen nanolithographic printing to generate organic/inorganic
solid state structures, which is hereby incorporated by reference
in its entirety.
[0043] Sol-gel chemistry can be used to practice the present
invention. For example, nanostructures and nanoarrays can be
prepared using the technologies of sol-gel chemistry and DPN
printing in combination. For the present invention, the sol-gel
process generally refers to a low temperature method using chemical
precursors that can produce ceramics and glasses with better purity
and homogeneity than high temperature conventional processes. This
process can be used to produce a wide range of compositions (for
example metal oxides) in various forms, including compositions
useful for powders, fibers, coatings/thin films, monoliths,
composites, and porous membranes. In the present invention,
organic/inorganic hybrids, where an inorganic gel is impregnated
with organic components such as polymers or organic dyes to provide
specific properties, can also be made. An attractive feature of the
sol-gel process is the capability to produce compositions not
possible with conventional methods. Another benefit is that the
mixing level of the solution is retained in the final product,
often on the molecular scale. For example, nanocomposites can be
made. Applications for sol-gel derived products, including those of
the present invention, are numerous. Applications include coatings
and thin films used in electronic, optical and electro-optical
components and devices, including optical absorption or
index-graded antireflective coatings. Other example devices include
capacitors, memory devices, substrates and infrared (IR) detectors.
Additional devices include thin film transistors, field effect
transistors, bipolar junction transistors, hybrid transistors,
charge transfer devices, field emission devices, integrated
circuits, solar cells, light emitting diodes, flat panel displays,
optical waveguides, and waveguide division multiplexers.
Antireflection coatings are also used for automotive and
architectural applications. Protective and decorative coatings can
also be made. Additional uses include dental and biomedical
applications as well as agrochemicals and herbicides. Glass
monoliths/coatings and inorganic/organic hybrids are under
development for lenses, mirror substrates, graded-index optics,
optical filters, chemical sensors, passive and nonlinear active
waveguides, lasers, and high resolution masks. Membranes for
separation and filtration processes also are being investigated, as
well as catalysts. More recently, biotechnology applications have
been developed, where biomolecules are incorporated into sol-gel
matrices. Applications include biochemical processes monitoring,
environmental testing, food processing, and drug delivery for
medicine or agriculture.
[0044] For purposes of the present invention, the sol-gel process
can be carried out in liquid solution of organometallic precursors,
which, by means of hydrolysis and condensation reactions, lead to
the formation of a new phase (sol).
M-O--R+H.sub.2O.fwdarw.M-OH+R--OH(hydrolysis)
M-OH+HO-M.fwdarw.M-O-M+H.sub.2O(water condensation)
M-O--R+HO-M.fwdarw.M-O-M+R--OH(alcohol condensation)
[0045] The sol can be made of solid particles suspended in a liquid
phase. Then the particles can condense in a new phase (gel) in
which a solid macromolecule is immersed in a liquid phase
(solvent). This is a gelatinous network. Drying the gel by means of
low temperature treatments (typically, for example, about
25.degree. C. to about 400.degree. C., and more typically about
25.degree. C. to about 100.degree. C.), results in porous solid
matrices (xerogels) which if desired can be calcined into a dense
ceramic. With use of rapid drying, aerogels can be made. An
important property of the sol-gel process is that it is possible to
generate glass or ceramic material at a temperature close to room
temperature.
[0046] In addition, sol-gel chemistry can be used to make
mesoporous structures from inorganic salts and polymer surfactants
(see, for example, reference 6). In the present invention, for
example, sol-gel reactions can be used to convert an inking
composition comprising at least one metal oxide precursor to the
corresponding metal oxide as inking composition is placed on the
tip, transferred from the tip to the substrate to form a deposit,
and subsequently processed. In a preferred embodiment, arrays,
microarrays, and nanoarrays can be prepared.
[0047] Use of sol-gel chemistry in nanotechnology is disclosed in,
for example, Fundamentals of Microfabrication, The Science of
Miniaturization, 2.sup.nd Ed., (2002), Marc J. Madou, CRC Press,
including for example, pages 156-157 and 368-369, which is hereby
incorporated by reference.
[0048] Arrays, microarrays, and nanoarrays are known in the art.
DPN printing, particularly parallel DPN printing, is also
especially useful for the preparation of arrays, and grids. An
array is an arrangement of a plurality of discrete sample areas, or
pattern units, forming a larger pattern on a substrate. The number
in this plurality is not particularly limited but can be, for
example, at least about 10, at least about 100, at least about
1,000, and at least about 10,000. It can be, in some cases, over
1,000,000. The sample areas, or patterns, may be any shape (e.g.,
dots, lines, circles, squares or triangles) and may be arranged in
any larger pattern (e.g., rows and columns, lattices, grids, etc.
of discrete sample areas). Each sample area may contain the same or
a different sample as contained in the other sample areas of the
array.
[0049] DPN printing, particularly parallel DPN printing, is
particularly useful for the preparation of nanoarrays and grids on
the submicrometer scale. An array on the submicrometer scale means
that at least one of the dimensions (e.g, length, width or
diameter) of the sample areas, excluding the depth or height, is
less than 1 .mu.m. In other words, at least one lateral dimension
of the deposit is about 1,000 nm or less. The lateral dimension can
be, for example, about 500 nm or less, or in other embodiments,
about 200 nm or less. Arrays on a submicrometer scale allow for
denser packing of devices. This typically results in faster overall
devices. The deposit can have a depth, or height, of about 50 nm or
less, or more particularly, about 8 nm or less.
[0050] DPN printing, for example, can be used to prepare nanoarray
dots that are approximately 1 micron in diameter or less,
approximately 500 nanometers in diameter or less, approximately 200
nanometers in diameter or less, approximately 100 nanometers in
diameter or less, approximately 50 nanometers in diameter or less,
or approximately 10 nanometers in diameter or less. With sharp
tips, dots can be produced about 1 nm in diameter.
[0051] DPN printing, for example, also can be used to prepare
nanoarray lines having widths that are approximately 1 micron or
less, approximately 500 nanometers or less, approximately 200
nanometers or less, approximately 100 nanometers or less,
approximately 50 nanometers or less, or approximately 10 nanometers
or less. With sharp tips, lines can be produced about 1 nm in
width.
[0052] The nanoarray can comprise nanostructures which are
separated by a distance of about 1,000 nm or less, and more
particularly, about 500 nm or less, and more particularly, about
200 nm or less. Separation distance can be measured by method known
in the art including AFM imaging.
[0053] DPN printing processes can involve depositing molecules
which do not generally undergo chemical reaction in solution during
printing. That is, the processes can concentrate on physical,
non-reactive transportation of the patterning or ink molecule from
the tip to the substrate followed by chemisorption or covalent
bonding to the substrate. This process works well for the
deposition and fabrication of organic layers. The deposition and
fabrication of layers comprising inorganic components, especially
ceramic and glass layers, can be effectively accomplished through a
reactive process, including for example, a sol-gel reactive
process. In other words, it can be a reactive DPN printing process.
Here, some of the constituents in the solution undergo chemical
reaction in the solution to form the deposition material.
[0054] In particular, DPN printing, and the aforementioned
procedures, instrumentation, and working examples, surprisingly can
be adapted also to fabricate solid state structures, especially
those comprising inorganic, metal oxide, and sol-gel materials as
described further herein. An embodiment is illustrated in FIG. 1,
which illustrates a nanoscopic AFM tip and a water meniscus. In
many cases, although the role of the meniscus is not entirely clear
and the present invention is not limited by theory, the inking
composition is transported from the tip to the substrate surface
via a water meniscus formed between the tip and substrate surface
under ambient conditions or conditions of relatively high humidity
such as, for example, more than about 40% (see, for example,
reference 2).
[0055] The type of nanoscopic tip and the type of substrate are not
particularly limited and the invention has broad applicability. For
example, the tip can be hollow or non-hollow. The substrate can be
primed with a primer layer or unprimed. If a primer is used,
multiple priming layers can be used. The substrate can be an
electrical insulator, an electrical semiconductor, or an electrical
conductor. Significantly, the methods described herein do not
require conducting substrates which makes the method more
versatile. Typical substrates include, but are not limited to,
silicon, SiO.sub.2, germanium, SiGe, GaAs, InP, AlGaAs, AlGaP,
AlGaInP, and GaP. The substrate can be primed, if desired, with a
relatively thin priming layer including, for example, a monolayer
or self-assembled monolayer. Multiple priming layers can be used
including two, three, four, or more layers.
[0056] Herein, new DPN printing-based methods for the direct
patterning of organic/inorganic composite nanostructures on
substrates such as, for example, silicon and oxidized silicon
substrates are disclosed. In a preferred embodiment, hydrolysis of
metal precursors, including metal oxide precursors, can be used.
The actual hydrolysis reaction depends on the precursor and the
hydrolysis product. A typical hydrolysis reaction is described by
the following equation:
2MCl.sub.n+nH.sub.2O.fwdarw.M.sub.2O.sub.n+2nHCl; where M is a
metal. The hydrolysis reaction may occur either in the "ink well"
prior to dipping the deposition tool (typically a nanoscopic tip
such as an SPM or AFM tip) and/or in the meniscus between the
nanoscopic deposition tool tip and the substrate surface.
[0057] The inks used in the present invention can be hybrid
composite solutions comprising, for example, inorganic salts (the
metal precursors) and surfactants such as, for example, amphiphilic
block copolymer surfactants. The metal precursor is typically a
metal halide, more typically a metal chloride. However, many other
metal precursors may be used and are known to those of ordinary
skill in the art. Exemplary metals include Al, Si, Sn, Ti, Zr, Nb,
Ta, W, In and Hf.
[0058] Surfactants can be used if desired. They can be ionic or
nonionic, cationic or anionic. They can be polymeric or
copolymeric. They can be amphilic, comprising a hydrophilic and a
hydrophobic component. The hydrophilic and hydrophobic components
of the surfactant can be adjusted to provide the desired DPN
printing method and structure. The copolymer surfactant, if used,
can perform a number of functions. For example, it can disperse and
stabilize the inorganic ink precursor, increase ink fluidity, and
act as a structure-directing agent for the materials that comprise
the patterned nanostructures (e.g., generate mesoporosity).
Particularly effective examples include block copolymer surfactants
such as copolymers of poly(alkylene oxides) including copolymeric
poly(ethylene oxides) and poly(propylene oxides). Of the
poly(alkylene oxides), poly (ethyleneoxide)-b-poly
(propyleneoxide)-b-poly (ethyleneoxide),
(EO.sub.20PO.sub.70EO.sub.20) (Pluronic P-123, BASF) has been found
to be particularly effective.
[0059] One type of product of reactive DPN printing can be an
oxides and metal oxides. Typical oxides include, but are not
limited to, Al.sub.2O.sub.3, SiO.sub.2, SnO.sub.2, TiO.sub.2,
ZrO.sub.2, Nb.sub.2O.sub.5, Ta.sub.2O.sub.5, WO.sub.3, HfO.sub.2,
In.sub.2O.sub.3. In addition, according to one embodiment of the
invention, it is also possible form mixed oxides. These include,
for example, SiAlO.sub.3.5, SiTiO.sub.4, ZrTiO.sub.4,
Al.sub.2TiO.sub.5, ZrWO.sub.8 and indium tin oxide (ITO).
[0060] The process of using reactive dip pen nanolithographic
printing can be similar to other nanolithographic printing
processes. For example, first, the ink or inking composition can be
made. In one embodiment of the invention, the ink can be made by
mixing a metal oxide precursor and an amphiphilic block copolymer
surfactant and allowing them to form a sol. Then, as in other DPN
printing processes, a nanoscopic tip such as an AFM tip is dipped
into the ink, picking up a small amount of sol. The nanoscopic tip
such as an AFM tip is then brought to the surface of the substrate
and the sol deposited. If desired, the nanoscopic tip can be
modified to improve the ability of the inking composition to coat
the tip and be transferred therefrom to the substrate.
[0061] In a second embodiment of the invention, the sol is not
formed in the ink well. As in the first embodiment, the first step
is to mix a metal precursor and an amphiphilic block copolymer
surfactant. However, in this embodiment, a nanoscopic tip such as
the AFM tip is dipped into the ink before the sol forms. In this
embodiment, the sol is formed on the nanoscopic tip.
[0062] Preferably, during deposition and transfer of the ink to the
substrate, the relative humidity is in the range of approximately
25% to approximately 95% and in a temperature range of
approximately 15.degree. C. and approximately 45.degree. C. A
particularly useful combination is a relative humidity of
approximately 30% to approximately 50% and a temperature of
20.degree. C. Typically, depositing is done by scanning an AFM tip
across the substrate at a rate between approximately 0.1 .mu.m/sec
and approximately 0.4 .mu.m/sec. One particularly useful rate is
0.2 .mu.m/sec.
[0063] During inking, transfer, and deposition, the ink can
comprise mesophases. The surfactant molecules or block copolymers
can form micelles or liquid crystalline phases in the solvent such
as water. These liquid crystalline phases include lamellar,
hexagonal, cubic structures. The length scale of these structures
can be, for example, about 1 nm to about 50 nm. Evaporation-induced
self-assembly can be used, which can be a spontaneous organization
of materials through non-covalent interactions induced by
evaporation.
[0064] The substrate can be heated at relatively low temperatures
after deposition to remove the organic moiety. The time and
temperature of post-deposition heat treatment is not particularly
limited. For example, temperature of up to about 900.degree. C. can
be used. The post deposition heat treatment can be typically
between 25.degree. C. and 500.degree. C., preferably between
300.degree. C. and 500.degree. C. The post deposition heat
treatment is typically between 0.5 and 4 hours. A particularly
useful combination is approximately 400.degree. C. for 2 hours.
Heating can be controlled to control shrinkage.
[0065] If an organic moiety is used in the ink, the organic can be
removed with heating. After removing the organic moiety, the result
can be, for example, a porous, microporous, or mesoporous metal
oxide. Pore sizes can be, for example, about 1 nm to about 50
nm.
[0066] DPN printing can be used to generate one molecule thick
structures through the controlled movement of an ink-coated AFM tip
on a desired substrate (see, for example, reference 1).
Significantly, reactive DPN printing allows one to prepare
solid-state structures with controlled geometry at the individual
molecule level. With the use of reactive DPN printing, arrays of
dots and lines can be written easily with control over feature size
and shape on the sub-200 nm level. Further, functional materials
can be added into sol inks (see, for example, reference 9). For
example in the case of catalysts, these types of structures could
be very important for initiating the growth of larger structures
(e.g. nanotubes) from a surface patterned with these materials.
[0067] The sol patterning process complements the larger scale
micromolding techniques (see, for example, reference 10) by
offering substantially higher resolution and the ability to make
multicomponent nanostructures with ultrahigh registry (see, for
example, reference 1b).
[0068] Four particularly preferred methods can be used in the
present invention.
[0069] In a first preferred embodiment, the present invention
provides a method of nanolithography comprising: providing a
substrate, providing a nanoscopic tip having an inking composition
thereon, wherein the inking composition comprises at least one
metal oxide precursor; transferring the inking composition from the
nanoscopic tip to the substrate to form a deposit on the substrate
comprising at least one metal oxide precursor. The method can
further comprise the step of inking the nanoscopic tip with the
inking composition prior to the transferring step to provide the
nanoscopic tip having inking composition thereon. Inking the
nanoscopic tip with inking composition can comprise forming the
inking composition and transferring the inking composition to the
end of the nanoscopic tip. The method can further comprise the step
of converting the metal oxide precursor on the substrate to form
the metal oxide by, for example, heating. The nanoscopic tip can be
a scanning probe microscopic tip, including both hollow and
non-hollow tips, and preferably an atomic force microscopic tip.
The deposit can have at least one lateral dimension which is about
1,000 nm or less, preferably about 200 nm or less. The deposit can
have a height of about 50 nm or less, more particularly, about 8 nm
or less. The substrate can be silicon or silicon oxide.
[0070] In addition, the present invention also provides a second
preferred embodiment: a method of nanolithography comprising
positioning a scanning probe microscopic tip having a reactive ink
composition thereon relative to a substrate so that the reactive
ink composition is transferred from the nanoscopic tip to the
substrate to form a deposit on the substrate, wherein the reactive
ink is a sol-gel precursor capable of undergoing a sol-gel
reaction. The invention can further comprise the step of heating
the deposit to substantially complete the sol-gel reaction.
[0071] In a third preferred embodiment, the invention provides a
method of nanolithography comprising patterning a nanoscopic
deposit comprising a solid state material precursor on a substrate,
and converting the solid state material precursor to the solid
state material. The solid state material can be an oxide, and
preferably a metal oxide. The solid state material can be
mesoporous.
[0072] Still further, the invention provides in a fourth preferred
embodiment a method of fabricating inorganic/organic nanostructures
comprising depositing an ink on a substrate by direct write
nanolithography to form a deposit, wherein the ink comprises an
inorganic precursor and at least one organic polymer. The ink can
be a sol, and the inorganic precursor can be a metal oxide
precursor. Patterns of dots and patterns of lines can be
formed.
[0073] Technical literature which can be used as a further guide in
practicing the present invention, including various combinations of
sol-gel technology and nanotechnology, include, for example, U.S.
Pat. Nos. 6,471,761 to Fan et al.; and 6,365,266 to McDougall et
al., each of which are hereby incorporated by reference. For
example, U.S. Pat. No. 6,471,761 discloses coating compositions
which can be used in the present invention comprising
tetraethoxysilane (TEOS), a surfactant, at least one organosilane,
HCl, water, and ethanol. A dye component can be used if desired.
The coating compositions can be patterned by methods including
micropen lithography. In addition, the disclosure found in the
article by Fan et al., Microporous and Mesoporous Materials, 44-45
(2001) 625-637 can be used to practice the present invention and is
hereby incorporated by reference.
[0074] In addition, U.S. Patent Publication No. 20020187335 A1
published Dec. 12, 2002 to Kelly et al. also can be used to
practice the present invention and is hereby incorporated by
reference. This reference discloses metal oxide coatings having
nanotextured surfaces defined by a plurality of capillary openings
arranged in a pattern on the surface of the coating. Each of the
capillary openings have a diameter defined by a previously present
organic macromolecule. The diameter can be, for example, less than
about 10 nm. The metal oxides can be ceramics characterized by high
hardness, wear resistance, corrosion resistance, abrasion
resistance, and thermal stability.
[0075] In addition, U.S. Pat. No. 6,380,266 to Katz et al. also can
be used to practice the invention and is hereby incorporated by
reference. This reference discloses amorphous inorganic materials
having pores of controlled size and shape with one or more
spatially organized functional groups formed therein. The
functional groups can be positioned in a defined three dimensional
relationship with the voids and with respect to each other. By
varying both the positions and identities of these functional
groups, diverse sets of substrate specific adsorbents and
non-biologically-based catalysts can be made. The organic group can
be covalently attached to the inorganic oxide.
[0076] Solid state materials, non-molecular solids, and metal
oxides which can be used in the present invention are generally
discussed in Cotton and Wilkinson, Advanced Inorganic Chemistry, A
Comprehensive Text, 4.sup.th Ed., including for example pages 1-27
which is hereby incorporated by reference. This includes substances
that exist in the solid state as extended arrays rather than
molecular units. These can be called nonmolecular substances or
structures.
[0077] In addition, the following reference can be used to practice
the present invention and is hereby incorporated by reference:
Yang, P. et al. Nature 1998, 396, 152. This discloses generalized
syntheses of large-pore mesoporous metal oxides with
semicrystalline frameworks.
[0078] In addition, the reference Vioux, A. Chem. Mater. 1997, 9,
2292 can be used to practice the present invention and is hereby
incorporated by reference. This reference discloses nonhydrolytic
sol-gel methods to form oxides including hydroxylation in
non-aqueous systems and aprotic condensation reactions.
[0079] Further, the reference Antonelli, D. et al. Angew. Chem.
Int. Ed. Engl. 1995, 34, 2014 can be used to practice the present
invention and is hereby incorporated by reference. It discloses,
for example, the synthesis of hexagonally packed mesoporous
titanium dioxide by a modified sol-gel route.
[0080] In addition, the reference Ichinose, I. et. al. Chem. Mater.
1997, 9, 1296 can be used to practice the present invention and is
hereby incorporated by reference. It discloses, for example, a
surface sol-gel process of titanium dioxide and other metal oxide
films with molecular precision.
[0081] Other references which can be used, include, for example:
Yang, P. et al. Science 2000, 287, 465; Lu, Y. et al. Nature 2001,
410, 913; and Fan, H. et al. Nature 2000, 405, 56; and Yang, P. et
al. Science 1998, 282, 2244, which are hereby incorporated by
reference.
[0082] The invention is further illustrated with use of the
following non-limiting working examples, which do not limit the
invention.
WORKING EXAMPLES
Experimental
[0083] A ThermoMicroscopes CP AFM and conventional silicon nitride
micro-cantilevers (force constant of 0.05 N/m) were used for all
patterning experiments. In each experiment, the tip was coated by
dipping it into the as-prepared sols at room temperature for 20
seconds. All patterning experiments were conducted under ambient
conditions without rigorous control over humidity (.about.40%) and
temperature (.about.20.degree. C.) with a tip-surface contact force
of 0.5 nN. To minimize the piezo tube drift, a 90 .mu.m scanner
with closed loop scan control was used for all patterning
experiments. Subsequent imaging of the generated patterns was done
with the ink-coated tip under conditions identical to those used
for patterning but at a higher scan rate (6 Hz).
[0084] In a typical experiment, an inorganic precursor solution
(sol) was prepared by dissolving 1 g of the block copolymer poly
(ethyleneoxide)-b-poly (propyleneoxide)-b-poly (ethyleneoxide),
(EO.sub.20PO.sub.70EO.sub.20) (Pluronic P-123, BASF) in 10 g of
ethanol and then adding 0.01 mol of the desired inorganic chloride
precursor. The mixture was stirred vigorously for 30 minutes to
generate the sol. The as-made sols were transparent fluids. The
ethanol slows the hydrolysis of the inorganic precursor (as
compared with water) (see references 7), and as a result the
gelation normally occurs after several hours and is not complete
until several days. This time frame allows one to easily do DPN
printing experiments, which for the ones described herein take only
a few minutes.
Examples 1 and 2
[0085] Dots, lines and complex patterns comprised of tin-oxide and
aluminum oxide have been generated on silicon and silicon oxide
(>600 nm oxidation layer) substrates, as shown in FIG. 2. For
example, 155 nm wide parallel lines made of tin-oxide have been
constructed on SiO.sub.2 by moving a tip coated with the composite
ink (SnCl.sub.4 and P-123) across the substrate (0.2 .mu.m/sec).
Similarly, dots consisting of Al.sub.2O.sub.3 were generated on a
Si substrate using a tip coated with (AlCl.sub.3 and P-123) by
successively bringing the tip in contact with substrate for 1 s/dot
intervals. These structures maintain their shapes even after
repeated imaging (5 times) and are indefinitely stable (>1
month) under ambient conditions.
Example 3
[0086] A Si sol (comprised of SiCl.sub.4 and P-123) was patterned
onto a silicon oxide substrate in the form of parallel lines. The
composition of the lines is expected to be a mixture of SiO.sub.x
and the polymer. When heated in air at 400.degree. C. for 2 hour,
the copolymer surfactant is expected to combust leaving a SiO.sub.2
nanostructure. Consistent with this hypothesis, an AFM image
collected from the same area post heating indicated that the
pattern height decreases from 8 nm to 5 nm, FIGS. 2c and 2d.
Example 4
[0087] The types of oxide structures that can be formed were not
particularly limited subject when sol precursors are generally
available. Indeed, tin-oxide structures have been prepared from
SnCl.sub.4 and P-123 on SiO.sub.2, Energy Dispersive X-Ray (EDX)
analysis of a 4 .mu.M SnO.sub.2 dot formed by holding the
ink-coated tip for 30 sec shows the expected peaks for tin, silicon
and oxygen, confirming the chemical identity of the microstructure
(FIG. 3a-3c). The copolymer used here is known as a
structure-directing agent for mesoscopic ordered solids.
Transmission Electron Microscope (TEM) images of bulk as-prepared
products (used as a control), after being heated at 400.degree. C.
for 2 h, show that the pore size for SiO.sub.2 is about 10 nm, FIG.
3d. These structures are believed to be chemisorbed to the
underlying substrate. Indeed, others have shown that when sols
hydrolyzed on oxide substrates, they form thin films that are
adsorbed to the substrates through silicon-oxygen-metal bonding
(see reference 8).
[0088] Finally, the nanostructures in FIG. 2 can undergo the same
structural transition as observed for the bulk material.
[0089] The following references are cited above, can be used to
practice the present invention, and are hereby incorporated by
reference in their entirety. [0090] (1) (a) Piner, R.; Zhu, J.; Xu,
F.; Hong, S.; Mirkin, C. A. Science 1999, 283, 661; (b) Hong, S.;
Zhu, J.; Mirkin, C. A. Science 1999, 286, 523; (c) Hong, S.;
Mirkin, C. A. Science 2000, 288, 1808. [0091] (2) Hong, S.; Zhu,
J.; Mirkin, C. A. Langmuir 1999, 15, 7897. [0092] (3) Ivanisevic,
A.; Mirkin, C. A. J. Am. Chem. Soc. 2001, 123, 7887. [0093] (4) (a)
Li, Y.; Maynor, B.; Liu, 1. J. Am. Chem. Soc. 2001, 123, 2105; (b)
Maynor, B.; Li, Y.; Liu, J. Langmuir 2001, 17, 2575. [0094] (5) (a)
Demers, L. M.; Mirkin, C. A. Angew. Chem. Int. Ed. 2001, 40, 3069;
(b) Demers, L. M.; Park, S.-J.; Taton, A.; Li, Z.; Mirkin, C. A.
Angew. Chem. Int. Ed. 2001, 40, 3071. [0095] (6) Yang, P.; Zhang,
D.; Margolese, D.; Chmelka, B.; Stucky, G. Nature 1998, 396, 152.
[0096] (7) (a) Vioux, A. Chem. Mater. 1997, 9, 2292; (b) Antonelli,
D.; Ying, J. Angew. Chem. Int. Ed. Engl. 1995, 34, 2014. [0097] (8)
Ichinose, I.; Senzu, H.; Kunitake, T. Chem. Mater. 1997, 9, 1296.
[0098] (9) (a) Kong, J.; Soh, H.; Cassell, A.; Quate, C.; Dai, H.
Nature 1998, 395, 878; (b) Yang, P.; Wimsberger, G.; Huang, H.;
Cordero, S.; McGehee, M.; Scott, B.; Deng, T.; Whitesides, G.;
Chmelka, B.; Buratto, S.; Stucky, G. Science 2000, 287, 465; (c)
Lu, Y.; Yang, Y.; Sellinger, A.; Lu, M.; Huang, J.; Fan, H.;
Haddad, R.; Lopez, G.; Burns, A.; Sasaki, D.; Shelnutt, J.;
Brinker, J. Nature 2001, 410, 913; (d) Fan, H.; Lu, Y.; Stump, A.;
Reed, S.; Baer, T.; Schunk, S.; Perez-Lunia, V.; Lopez, G.;
Brinker, J. Nature 2000, 405, 56. [0099] (10) Yang, P.; Deng, T.;
Zhao, D.; Feng, P.; Pine, D.; Chmelka, B.; Whitesides, G.; Stucky,
G. Science 1998, 282, 2244.
* * * * *