U.S. patent application number 13/592852 was filed with the patent office on 2013-08-29 for atomic force microscope probe.
This patent application is currently assigned to HON HAI PRECISION INDUSTRY CO., LTD.. The applicant listed for this patent is SHOU-SHAN FAN, YANG WEI. Invention is credited to SHOU-SHAN FAN, YANG WEI.
Application Number | 20130227749 13/592852 |
Document ID | / |
Family ID | 48952321 |
Filed Date | 2013-08-29 |
United States Patent
Application |
20130227749 |
Kind Code |
A1 |
WEI; YANG ; et al. |
August 29, 2013 |
ATOMIC FORCE MICROSCOPE PROBE
Abstract
An atomic force microscope probe includes a carbon nanotube
micro-tip structure. The carbon nanotube micro-tip structure
includes an insulating substrate and a patterned carbon nanotube
film structure. The insulating substrate includes a surface. The
surface includes an edge. The patterned carbon nanotube film
structure is partially arranged on the surface of the insulating
substrate. The patterned carbon nanotube film structure includes
two strip-shaped arms joined together to form a tip portion
protruding and suspending from the edge of the surface of the
insulating substrate. The two strip-shaped arms include a number of
carbon nanotubes parallel to the surface of the insulating
substrate.
Inventors: |
WEI; YANG; (Beijing, CN)
; FAN; SHOU-SHAN; (Beijing, CN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
WEI; YANG
FAN; SHOU-SHAN |
Beijing
Beijing |
|
CN
CN |
|
|
Assignee: |
HON HAI PRECISION INDUSTRY CO.,
LTD.
Tu-Cheng
TW
TSINGHUA UNIVERSITY
Beijing
CN
|
Family ID: |
48952321 |
Appl. No.: |
13/592852 |
Filed: |
August 23, 2012 |
Current U.S.
Class: |
850/40 ; 977/742;
977/953 |
Current CPC
Class: |
B82Y 15/00 20130101;
G01Q 70/12 20130101; B82Y 35/00 20130101; H01J 1/304 20130101; G01Q
60/40 20130101; H01J 1/14 20130101 |
Class at
Publication: |
850/40 ; 977/742;
977/953 |
International
Class: |
G01Q 60/38 20100101
G01Q060/38 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 23, 2012 |
CN |
201210042269.7 |
Claims
1. An atomic force microscope probe comprising: a carbon nanotube
micro-tip structure, the carbon nanotube micro-tip structure
comprising: an insulating substrate comprising a surface, the
surface comprising an edge; and a patterned carbon nanotube film
structure partially arranged on the surface of the insulating
substrate, the patterned carbon nanotube film structure comprising
two strip-shaped arms joined together forming a tip portion
protruding and suspending from the edge of the surface of the
insulating substrate, each of the two strip-shaped arms comprising
a plurality of carbon nanotubes parallel to the surface of the
insulating substrate.
2. The atomic force microscope probe of claim 1, wherein an angle
.alpha. between a length directions of the two strip-shaped arms is
smaller than 180.degree..
3. The atomic force microscope probe of claim 1, wherein the each
of the two strip-shaped arms comprising comprises a plurality of
carbon nanotube films stacked together, each of the plurality of
carbon nanotube films comprises the plurality of carbon nanotubes
substantially aligned along a same direction, and an angle .beta.
between the plurality of carbon nanotubes in different carbon
nanotube films is in a range of
0.degree.<.beta..ltoreq.90.degree..
4. The atomic force microscope probe of claim 1, wherein the
patterned carbon nanotube film structure further comprises two
connecting portions respectively connected to the two strip-shaped
arms and located on the surface of the insulating substrate, the
two strip-shaped arms entirely protrude and suspend from the edge
of the surface of the insulating substrate.
5. The atomic force microscope probe of claim 1, wherein each of
the two strip-shaped arms has a first end and a second end along a
length direction of the strip-shaped arm, and a width gradually
decreasing from the second end to the first end, the two
strip-shaped arms are joined at the first end.
6. The atomic force microscope probe of claim 1, wherein the
patterned carbon nanotube film structure further defines a cutout,
a lengthwise direction of the cutout is parallel to the surface of
the insulating substrate, and extends from a direction from the
edge to the tip portion.
7. The atomic force microscope probe of claim 6, wherein the two
strip-shaped arms are symmetrical about a symmetry axis, and the
lengthwise direction of the cutout is on the symmetry axis.
8. The atomic force microscope probe of claim 3, wherein the two
strip-shaped arms are symmetrical about a symmetry axis, the
plurality of carbon nanotubes in at least one of the plurality of
carbon nanotube films of the patterned carbon nanotube film
structure are parallel to the symmetry axis.
9. The atomic force microscope probe of claim 1, wherein the two
strip-shaped arms are symmetrical about a symmetry axis, the edge
of the surface is straight, and the symmetry axis is perpendicular
to the edge.
10. The atomic force microscope probe of claim 1, wherein the two
strip-shaped arms comprise a blade-shaped thickness that is thicker
at a middle of the strip-shaped arms than at an edge of the two
strip-shaped arms.
11. The atomic force microscope probe of claim 1, wherein the
patterned carbon nanotube film structure comprises a plurality of
carbon nanotubes protruding from the tip portion and spaced from
each other.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims all benefits accruing under 35
U.S.C. .sctn.119 from China Patent Application No. 201210042269.7,
filed on 2012 Feb. 23 in the China Intellectual Property Office.
This application is related to common-assigned applications
entitled, "CARBON NANOTUBE BASED MICRO-TIP STRUCTURE AND METHOD FOR
MAKING THE SAME" filed ______ (Atty. Docket No. US45096); "CARBON
NANOTUBE BASED MICRO-TIP STRUCTURE AND METHOD FOR MAKING THE SAME"
filed ______ (Atty. Docket No. US45095); "FIELD EMISSION ELECTRON
SOURCE AND FIELD EMISSION DEVICE USING THE SAME" filed ______
(Atty. Docket No. US45101); and "THERMIONIC EMISSION DEVICE" filed
______ (Atty. Docket No. US45817).
BACKGROUND
[0002] 1. Technical Field
[0003] The present disclosure relates to an atomic force microscope
probe, and particularly relates to a carbon nanotube based atomic
force microscope probe.
[0004] 2. Description of Related Art
[0005] Carbon nanotubes are carbon tubules having a diameter of 0.5
nanometers to 100 nanometers, and composed of a number of coaxial
cylinders of graphite sheets. Because the size of the carbon
nanotube is extremely small, it is difficult to precisely arrange
the carbon nanotube when manufacturing a carbon nanotube based
micro sized device. Although a microscope can be used during the
manufacturing process to observe the carbon nanotube, a batch of
substantially similar micro sized devices are difficult to
manufacture by operating the individual carbon nanotubes under the
microscope. Therefore, the carbon nanotube based micro sized device
is difficult to produce.
[0006] What is needed, therefore, is to provide an atomic force
microscope probe which has a relatively good performance and easily
to be manufactured.
BRIEF DESCRIPTION OF THE DRAWINGS
[0007] Many aspects of the embodiments can be better understood
with reference to the following drawings. The components in the
drawings are not necessarily to scale, the emphasis instead being
placed upon clearly illustrating the principles of the present
disclosure. Moreover, in the drawings, like reference numerals
designate corresponding parts throughout the several views.
[0008] FIG. 1 is a schematic top view of one embodiment of a carbon
nanotube micro-tip structure.
[0009] FIG. 2 is a scanning electron microscope (SEM) image of a
carbon nanotube film drawn from a carbon nanotube array.
[0010] FIG. 3 is an SEM image of one embodiment of a multi-layer
structure having a plurality of carbon nanotube films stacked with
each other and having carbon nanotubes aligned along different
directions.
[0011] FIG. 4 is a schematic top view of one embodiment of a
protruding section of a patterned carbon nanotube film
structure.
[0012] FIG. 5 is an SEM image of one embodiment of the protruding
section of the patterned carbon nanotube film structure.
[0013] FIG. 6 is a transmission electron microscope (TEM) image of
one embodiment of a tip portion of the patterned carbon nanotube
film structure.
[0014] FIG. 7 is a TEM image of one embodiment of carbon nanotubes
in the tip portion of the patterned carbon nanotube film
structure.
[0015] FIG. 8 is an SEM image of another embodiment of the tip
portion of the patterned carbon nanotube film structure.
[0016] FIG. 9 is a schematic top view of another embodiment of an
array of carbon nanotube micro-tip structures.
[0017] FIG. 10 is a schematic top view of another embodiment of the
carbon nanotube micro-tip structure.
[0018] FIG. 11 is a schematic top view of still another embodiment
of the carbon nanotube micro-tip structure.
[0019] FIG. 12 is a flowchart of one embodiment of a method for
making the carbon nanotube micro-tip structure.
[0020] FIG. 13 is a schematic structural view of one embodiment of
the method for making the carbon nanotube micro-tip structure.
[0021] FIG. 14 is a schematic structural view of one embodiment of
the method for making the carbon nanotube micro-tip structure
including a method (1).
[0022] FIG. 15 is a schematic structural view of another embodiment
of the method for making the carbon nanotube micro-tip structure
including a method (2).
[0023] FIG. 16 is a schematic structural view of still another
embodiment of the method for making the carbon nanotube micro-tip
structure including a method (3).
[0024] FIG. 17 is a cross-sectional view of an insulating substrate
having an assisted etching groove.
[0025] FIG. 18 is a top view of another embodiment of an array of
the carbon nanotube micro-tip structures.
[0026] FIG. 19 is an optical photo of one embodiment of an array of
the carbon nanotube micro-tip structures illuminated in vacuum.
[0027] FIG. 20 shows a test curve of a relationship between a
temperature at the tip portion of one embodiment of the carbon
nanotube micro-tip structure and a voltage.
[0028] FIG. 21 shows a test curve of a relationship between a
temperature at the tip portion of one embodiment of the carbon
nanotube micro-tip structure and a power.
[0029] FIG. 22 is a schematic top view of one embodiment of a field
emission device.
[0030] FIG. 23 shows test curves of a current-voltage relationship
of one embodiment of the carbon nanotube micro-tip structure at
room temperature and high temperature.
[0031] FIG. 24 shows field emitting current response curves of one
embodiment of the carbon nanotube micro-tip structure at
alternating temperatures from room temperature to high
temperature.
[0032] FIG. 25 shows test curves of a current-voltage relationship
of the carbon nanotube micro-tip structure at different
temperatures.
[0033] FIG. 26 is a schematic top view of one embodiment of an
atomic force microscope probe.
DETAILED DESCRIPTION
[0034] The disclosure is illustrated by way of example and not by
way of limitation in the figures of the accompanying drawings in
which like references indicate similar elements. It should be noted
that references to "an" or "one" embodiment in this disclosure are
not necessarily to the same embodiment, and such references mean at
least one.
[0035] Referring to FIG. 1, one embodiment of a carbon nanotube
micro-tip structure 100 includes an insulating substrate 110 and a
patterned carbon nanotube film structure 120. The insulating
substrate 110 includes a surface 112. The surface 112 has an edge
114. The patterned carbon nanotube film structure 120 is partially
arranged on the surface 112 of the insulating substrate 110. The
patterned carbon nanotube film structure 120 includes two
strip-shaped arms 122. The two strip-shaped arms 122 can be narrow
and long film shapes. The two strip-shaped arms 122 are joined at
one end to form a tip portion 124 of the patterned carbon nanotube
film structure 120. An angle .alpha. between lengthwise directions
of the two strip-shaped arms 122 can be smaller than 180.degree..
The tip portion 124 of the patterned carbon nanotube film structure
120 protrudes from the edge 114 of the surface 112 of the
insulating substrate 110 and is suspended. The patterned carbon
nanotube film structure 120 includes a plurality of carbon
nanotubes substantially parallel to the surface 112 of the
insulating substrate 110.
[0036] The insulating substrate 110 can be a board or a sheet. A
material of the insulating substrate 110 can be silicon, ceramic,
glass, resin, or crystal. The insulating substrate 110 can also be
a silicon substrate having a silicon oxide layer coated on the
surface 112. A thickness of the silicon oxide layer can be about 1
micron. An entire thickness of the insulating substrate 110 can be
about 0.5 millimeters.
[0037] The patterned carbon nanotube film structure 120 can be a
free-standing film shaped structure and can include a plurality of
carbon nanotube films stacked together. Each carbon nanotube film
may include a plurality of carbon nanotubes substantially aligned
along the same direction. The carbon nanotube film can be an
ordered and free-standing carbon nanotube film.
[0038] Referring to FIG. 2, the ordered and free-standing carbon
nanotube film can be drawn from a carbon nanotube array. The carbon
nanotube film can include or consist of a plurality of carbon
nanotubes. In the carbon nanotube film, the overall aligned
direction of a majority of carbon nanotubes is substantially
aligned along the same direction parallel to a surface of the
carbon nanotube film. A majority of the carbon nanotubes are
substantially aligned along the same direction in the carbon
nanotube film. Along the aligned direction of the majority of
carbon nanotubes, each carbon nanotube is joined to adjacent carbon
nanotubes end to end by van der Waals attractive force
therebetween, whereby the carbon nanotube film is capable of being
free-standing structure. There may be a minority of carbon
nanotubes in the carbon nanotube film that are randomly aligned.
However, the number of the randomly aligned carbon nanotubes is
very small and does not affect the overall oriented alignment of
the majority of carbon nanotubes in the carbon nanotube film. The
majority of the carbon nanotubes in the carbon nanotube film that
are substantially aligned along the same direction may not be
exactly straight, and can be curved at a certain degree, or are not
exactly aligned along the overall aligned direction, and can
deviate from the overall aligned direction by a certain degree.
Therefore, partial contacts can exist between the juxtaposed carbon
nanotubes in the majority of the carbon nanotubes aligned along the
same direction in the carbon nanotube film. The carbon nanotube
film may include a plurality of successive and oriented carbon
nanotube segments. The plurality of carbon nanotube segments are
joined end to end by van der Waals attractive force. Each carbon
nanotube segment includes a plurality of carbon nanotubes
substantially parallel to each other, and the plurality of
paralleled carbon nanotubes are in contact with each other and
combined by van der Waals attractive force therebetween. The carbon
nanotube segment has a desired length, thickness, uniformity, and
shape. There can be clearances between adjacent and juxtaposed
carbon nanotubes in the carbon nanotube film. A thickness of the
carbon nanotube film at the thickest location is about 0.5
nanometers to about 100 microns (e.g., in a range from 0.5
nanometers to about 10 microns).
[0039] The term "free-standing" includes, but not limited to, a
carbon nanotube film that does not have to be supported by a
substrate. For example, a free-standing carbon nanotube film can
sustain the weight of itself when it is hoisted by a portion
thereof without any significant damage to its structural integrity.
So, if the free-standing carbon nanotube film is placed between two
separate supporters, a portion of the free-standing carbon nanotube
film, not in contact with the two supporters, can be suspended
between the two supporters and yet maintain a film structural
integrity. The free-standing carbon nanotube film is realized by
the successive carbon nanotubes joined end to end by van der Waals
attractive force.
[0040] Referring to FIG. 3, in the patterned carbon nanotube film
structure 120, the plurality of ordered carbon nanotube films are
stacked together along at least two directions, such that the
carbon nanotubes in the carbon nanotube films stacked along
different directions are aligned along different directions. An
angle .beta. between the carbon nanotubes in the carbon nanotube
films stacked along different directions can be in a range of
0.degree..beta..ltoreq.90.degree.. The number of the carbon
nanotube films in the patterned carbon nanotube film structure 120
is not limited, and can be determined by actual needs. In some
embodiment, the patterned carbon nanotube film structure 120 can
include 5 to 100 stacked carbon nanotube films. In one embodiment,
the patterned carbon nanotube film structure 120 includes 50
stacked carbon nanotube films having the angle .beta. of about
90.degree. between the carbon nanotubes of adjacent carbon nanotube
films. The patterned carbon nanotube film structure 120 is a stable
free-standing film structure because the adjacent carbon nanotubes
directly contacting each other are sufficiently joined by van der
Waals attractive forces. In the patterned carbon nanotube film
structure 120, the adjacent carbon nanotubes are connected with
each other, thus forming an electrically conductive network. The
carbon nanotube film has an extremely thin thickness. Accordingly,
the patterned carbon nanotube film structure 120 having the
plurality carbon nanotube films stacked together can have a small
thickness. In one embodiment, the thickness of the patterned carbon
nanotube film structure 120 having 50 carbon nanotube films stacked
together is in a range from about 50 nanometers to about 5 microns.
The carbon nanotube film can have a uniform thickness. Accordingly,
the patterned carbon nanotube film structure 120 having the
plurality carbon nanotube films stacked together can have a uniform
thickness, thus having a uniform electrical conductivity.
[0041] The patterned carbon nanotube film structure 120 is laid on
the surface 112 of the insulating substrate 110. Due to the
free-standing property, a portion of the patterned carbon nanotube
film structure 120 protruding from the edge 114 of the surface 112
can be suspended and remain parallel to the surface 112 of the
insulating substrate 110. That is, the carbon nanotubes in the
suspended portion of the patterned carbon nanotube film structure
120 are still parallel to the surface 112 of the insulating
substrate 110.
[0042] Referring to FIG. 4 and FIG. 5, in the patterned carbon
nanotube film structure 120, the two strip-shaped arms 122 are part
of an integrated structure formed by patterning a carbon nanotube
film structure. The integrated structure can have a V shape or a U
shape to form the two strip-shaped arms 122. Each strip-shaped arm
122 has a first end 1220 and a second end 1222 along the lengthwise
direction. The two strip-shaped arms 122 are joined together at the
first end 1220 to form a tip portion 124. The angle .alpha. between
the lengthwise directions of the two strip-shaped arms 122 can be
smaller than 180.degree.. In some embodiment, the angle .alpha. can
be in a range from about 15.degree. to about 120.degree.. In one
embodiment, the angle .alpha. is about 60.degree.. The tip portion
124 can have a size smaller than 20 microns. In one embodiment, the
tip portion 124 can only have a single protruding carbon nanotube
having a diameter of about 0.5 nanometers. The patterned carbon
nanotube film structure 120 can only protrude and suspend the tip
portion 124 or can protrude and suspend the entire two strip-shaped
arms 122 from the edge 114 of the surface 112 of the insulating
substrate 110. The shape of the two strip-shaped arms 122 are not
limited but have an overall strip shape. In one embodiment, each
strip-shaped arm 122 has a gradually decreased width from the
second end 1222 to the first end 1220, to have the resistance
gradually increased from the second end 1222 to the first end 1220,
which may be useful for a thermionic emission device or a thermal
field emission device. In another embodiment, each strip-shaped arm
122 has a uniform width from the second end 1222 to the first end
1220. The width of the strip-shaped arm 122 is not limited and can
be in a range from about 10 microns to about 1 millimeter. The
width at the first end 1222 can be in a range from about 10 microns
to about 300 microns.
[0043] The strip-shaped arm 122 can have a uniform thickness or a
blade-shaped thickness that is thicker at the middle of the
strip-shaped arm 122 compared to the thickness at the edge of the
strip-shaped arm 122. Referring to FIG. 5, the strip-shaped arm 122
has a light color at the middle and a gradually darkened color from
the middle to the edge. This shows that the edge of the
strip-shaped arm 122 is thinner than the middle of the strip-shaped
arm 122. The thickness of the strip-shaped arm 122 at the edge can
be nanosize (e.g., smaller than 100 nanometers). The blade-shaped
thickness that is thicker at the middle of the strip-shaped arm 122
may have a relatively good field emission performance in the field
emission device.
[0044] The two strip-shaped arms 122 can be reflection symmetrical
about a symmetry axis passing through the tip portion 124. In the
patterned carbon nanotube film structure 120, at least one carbon
nanotube film can have the majority of carbon nanotubes aligned
along the symmetry axis. In one embodiment, the edge 114 of the
surface 112 is straight, and the symmetry axis can be perpendicular
to the edge 114. Referring to FIG. 6, in one embodiment, the
symmetry axis is perpendicular to the edge 114, half of the carbon
nanotube films have the carbon nanotubes aligned along the symmetry
axis and the other half of the carbon nanotube films have the
carbon nanotubes aligned perpendicular to the symmetry axis.
Referring to FIG. 7, in one embodiment, the carbon nanotubes at the
tip portion 124 can have an open end (as pointed by the arrow in
the FIG. 7), which may facilitate the electron emission in the
field emission device.
[0045] The smaller width at the first end 1220 of the two
strip-shaped arms 122 may facilitate the electron emission in the
field emission device. The patterned carbon nanotube film structure
120 can further include a cutout 128 at the joining portion of the
two strip-shaped arms 122. The cutout 128 can be a line shape. The
lengthwise direction of the cutout 128 can be parallel to the
surface 112 of the insulating substrate 110, and extend along a
direction from the edge 114 to the tip portion 124. The width of
the cutout 128 can be uniform or gradually decreasing from the edge
114 to the tip portion 124. A distance exists from the end of the
cutout 128 to the top of the tip portion 124, where the two
strip-shaped arms 122 join together. In one embodiment, the
distance from the end of the cutout 128 to the top of the tip
portion 124 is about 210 microns. The resistance at the tip portion
124 can be increased by defining the cutout 128 in the patterned
carbon nanotube film structure 120, which may improve the thermal
emission performance or thermal field emission performance. In one
embodiment, the two strip-shaped arms 122 are symmetrical about the
symmetry axis, and the lengthwise direction of the cutout 128 can
be along the symmetry axis. The patterned carbon nanotube film
structure 120 can be seen as a bent conductive strip having the
narrowest width and greatest resistance at the tip portion 124.
[0046] Referring back to FIG. 1, to facilitate the connection
between the patterned carbon nanotube film structure 120 and an
outer circuit and while supporting the suspended portion, the
patterned carbon nanotube film structure 120 can further include
two connecting portions 126. The two connecting portions 126 are
respectively connected to the two strip-shaped arms 122 and located
on the surface 112 of the insulating substrate 110. Similar to the
two strip-shaped arms 122, the two connecting portions 126 are also
formed by patterning the carbon nanotube film structure. The two
connecting portions 126 and the two strip-shaped arms 122 are part
of the integrated structure. The shape of the connecting portion
126 is not limited. In one embodiment, the connecting portion 126
has a rectangular strip shape having the same width as the second
end 1222 of the strip-shaped arm 122.
[0047] The tip portion 124, the two connecting portions 126, and
the two strip-shaped arms 122 are portions of the integrated
structure (i.e., the integrated patterned carbon nanotube film
structure 120). In one embodiment, the patterned carbon nanotube
film structure 120 only includes the carbon nanotubes.
[0048] Referring to FIG. 8, another embodiment of the carbon
nanotube micro-tip structure is similar to the carbon nanotube
micro-tip structure 100 except that the patterned carbon nanotube
film structure 120 includes a plurality of carbon nanotubes
protruding from the tip portion 124. The plurality of protruded
carbon nanotubes extend radially from the tip portion 124 and are
spaced from each other, to form a plurality of micro-tips at the
tip portion 124 in a microscopic view. In one embodiment of a field
emission device having this carbon nanotube micro-tip structure,
the plurality of micro-tips can emit more electrons to an anode.
The plurality of protruded carbon nanotubes also belong to the
patterned carbon nanotube film structure 120, and are integrated to
the two strip-shaped arms 122. The plurality of protruded carbon
nanotubes are joined to the carbon nanotubes in the two
strip-shaped arms 122 by van der Waals attractive force.
[0049] Referring to FIG. 9, one embodiment of an array of carbon
nanotube micro-tip structures 200 includes an insulating substrate
210 and a plurality of patterned carbon nanotube film structures
220. The plurality of patterned carbon nanotube film structures 220
are spaced from each other and partially located on a surface 212
of the insulating substrate 210. The insulating substrate 210 and
the patterned carbon nanotube film structures 220 are similar to
the above embodiment of the insulating substrate 110 and the
patterned carbon nanotube film structure 120.
[0050] The difference is that a strip-shaped recess 216 is defined
in the insulating substrate 210 at the surface 212. The edge 214 of
the insulating substrate 212 having the portion of the patterned
carbon nanotube film structures 220 protruding therefrom is an edge
of the strip-shaped recess 216. The plurality of patterned carbon
nanotube film structures 220 at the tip portions 224 protrude from
the same edge 214 of the insulating substrate 210 and suspend above
the strip-shaped recess 216. The strip-shaped recess 214 can be a
blind groove or a through hole. In one embodiment, the strip-shaped
recess 216 is a strip-shaped through hole.
[0051] In the embodiment as shown in FIG. 9, the insulating
substrate 210 can define a plurality of spaced strip-shaped
recesses 216 to have a plurality of edges 214. The plurality of
strip-shaped recesses 216 can be parallel to each other. Each edge
214 of the surface 212 of the insulating substrate 210 can have a
plurality of tip portions 224 of the patterned carbon nanotube film
structures 220 protrude therefrom. In one embodiment, each edge 214
has the same number of protruded tip portions 224. In one
embodiment, the patterned carbon nanotube film structures 220 at
different strip-shaped recesses 216 are in accordance with each
other to form an m.times.n array, wherein m is the number of the
strip-shaped recesses 216, n is the number of the patterned carbon
nanotube film structures 220 at each strip-shaped recess 216,
m.gtoreq.1, and n.gtoreq.1.
[0052] Referring to FIG. 10, another embodiment of an array of
carbon nanotube micro-tip structures 300 similar to the above
embodiment of array of carbon nanotube micro-tip structures 200,
except that in the array of carbon nanotube micro-tip structures
300, the patterned carbon nanotube film structure 320 includes a
plurality of strip-shaped arms 322 and a plurality of tip portions
324 formed by the plurality of strip-shaped arms 322. The plurality
of strip-shaped arms 322 are joined end to end to form a
zigzag-shaped structure having a plurality of tip portions 324 at
two opposite directions of the patterned carbon nanotube film
structure 320. The insulating substrate 310 may only support the
two strip-shaped arms 322 at the ends of the zigzag-shaped
structure, and the other strip-shaped arms 322 suspended
therebetween.
[0053] Referring to FIG. 11, another embodiment of an array of
carbon nanotube micro-tip structures 400 is similar to the above
embodiment of array of carbon nanotube micro-tip structures 300,
except that in the array of carbon nanotube micro-tip structures
400, the plurality of strip-shaped arms 422 are joined end to end
to form a serrated structure having a plurality of tip portions 424
at two opposite directions of the patterned carbon nanotube film
structure 420. The insulating substrate 410 may only support the
two strip-shaped arms 422 at the ends of the serrated structure,
and the other strip-shaped arms 422 suspended therebetween. The
patterned carbon nanotube film structure 320 may also define a
strip-shaped cutout 426 extended along a direction from one tip
portion 424 to the opposite tip portion 424. Distances are defined
from two ends of the cutout 426 to the two opposite tip portions
424. The strip-shaped through cutout 426 can increase the
resistance at the tip portion 424.
[0054] Referring to FIG. 12 and FIG. 13, one embodiment of a method
for making the carbon nanotube micro-tip structure includes steps
of:
[0055] S1, providing a carbon nanotube film structure 10 and an
insulating substrate 20, wherein the insulating substrate 20 has a
surface 22, and at least one strip-shaped recess 26 is defined in
the insulating substrate 22 at the surface 22;
[0056] S2, covering the carbon nanotube film structure 10 on the
surface 22 of the insulating substrate 20, and having a suspended
portion of the carbon nanotube film structure 10 suspended over the
at least one strip-shaped recess 26; and
[0057] S3, laser etching the suspended portion of the carbon
nanotube film structure 10 to define a first hollow pattern 14 in
the suspended portion and form a patterned carbon nanotube film
structure 30 according to the first hollow pattern 14, wherein the
patterned carbon nanotube film structure 30 includes two
strip-shaped arms 32 joined at one end to form a tip portion 34.
The tip portion 34 is suspended above the strip-shaped recess
26.
[0058] In the step S1, the carbon nanotube film structure 10 can be
formed by steps of:
[0059] S11, providing a plurality of carbon nanotube films;
[0060] S12, stacking the plurality of carbon nanotube films along
different directions on a frame; and
[0061] S13, treating the plurality of carbon nanotube films on the
frame using an organic solvent to form a carbon nanotube film
structure 10.
[0062] The carbon nanotube film can be drawn from a carbon nanotube
array. The carbon nanotube film includes a plurality of carbon
nanotubes joined end to end by van der Waals attractive force
therebetween and aligned along substantially the same direction.
The carbon nanotube films can be covered on the frame one by one to
laminate together and suspend across the frame. The stacking
directions of carbon nanotube films can be different, or the carbon
nanotube films can be stacked along only several (e.g., two)
directions. The carbon nanotube film structure is a free-standing
structure supported only by the frame and suspended across the
frame. In one embodiment, the frame has a square shape with each
edge having a length of about 72 millimeters, and 50 carbon
nanotube films are stacked on the frame. The carbon nanotube film
is treated by applying the organic solvent to the drawn carbon
nanotube film to soak the entire surface of the stacked carbon
nanotube films and then removing the organic solvent by drying. In
the step S13, the carbon nanotube films can be soaked by the
organic solvent. The organic solvent can be a volatile solvent at
room temperature such as an ethanol, methanol, acetone,
dichloroethane, chloroform, or any appropriate mixture thereof.
After being soaked by the organic solvent, the adjacent carbon
nanotube films can be combined together by surface tension of the
organic solvent when the organic solvent volatilizes until the
stable carbon nanotube film structure 10 is achieved. The method
for drawing and stacking the carbon nanotube films are taught in US
patent publication number 2008/0248235A1.
[0063] In the step S1, the insulating substrate 20 can be etched or
laser cut to form a plurality of strip-shaped recesses 26 at the
surface 22. In one embodiment, the strip-shaped recesses 26 are a
plurality of strip-shaped through holes formed by using a reactive
iron etching (RIE) method. In the step S1, a plurality of spaced
strip-shaped recesses 26 can be formed on the insulating substrate
20 to prepare an array of carbon nanotube micro-tip structures or a
batch of carbon nanotube micro-tip structures. The plurality of
spaced strip-shaped recesses 26 can be parallel to each other in
the lengthwise direction.
[0064] In the step S2, the previously formed carbon nanotube film
structure 10 is laid on the surface 22 of the insulating substrate
20. After the step S2 of covering the carbon nanotube film
structure 10 on the surface 22 of the insulating substrate 20, an
additional step of treating the carbon nanotube film structure 10
with the organic solvent similar to the step S13, can be processed.
After the carbon nanotube film structure 10 is soaked by the
organic solvent and the organic solvent is volatilized from the
carbon nanotube film structure 10, the carbon nanotube film
structure 10 can be combined tightly with the surface 22 of the
insulating substrate 20, thus fixing the carbon nanotube film
structure 10 on the insulating substrate 20.
[0065] In the step S3, a laser device is provided to emit a laser
beam. The carbon nanotube film structure 10 is irradiated by the
laser beam which is focused on the surface of the carbon nanotube
film structure 10 to burn the irradiated portions of the carbon
nanotube film structure 10. The laser beam scans the portions of
the carbon nanotube film structure 10 to be etched out. The laser
etching is carried out in an environment with oxygen, for example,
in air. The carbon nanotubes in the irradiated portions absorb the
laser beam energy, react with the oxygen in the air, and then
decompose. Thus, the carbon nanotubes in the irradiated portions
will be removed. The laser device can have a power of approximately
2 watts to about 50 watts. A scanning rate of the laser beam can be
about 0.1 millimeter/second to about 10000 millimeter/second. A
width of the laser beam can be about 1 micron to about 400 microns.
In one embodiment, the laser device is an yttrium aluminum garnet
laser device having a wavelength of about 1.06 microns, a power of
about 3.6 watts, and a scanning rate of about 100
millimeter/second. Referring back to FIG. 5, due to the laser
etching, the etched edge of the carbon nanotube film structure 10
formed by the laser etching has a blade-shaped thickness (i.e., the
closer to the edge, the smaller the thickness). Thus, the two
strip-shaped arms 32 and the tip portion 34 formed by the laser
etching step can have the blade-shaped thickness. Referring back to
FIG. 7, due to the laser etching, some of the outermost carbon
nanotubes which may be partially etched by the laser beam have an
open end at the etched edge.
[0066] Referring back to FIG. 6, in a microscopic view, the laser
etching may form a relatively smooth top of the tip portion 34. To
facilitate the field emission, an additional step of protruding the
carbon nanotubes from the top of the tip portion 34 can be further
processed. Specifically, in this additional step, some carbon
nanotubes on the top of the tip portion 34 can be grabbed by a tool
and pulled out from the top of the tip portion 34. The tool can be
an adhesive such as a glue rod or an adhesive tape. The adhesive
can grab the carbon nanotubes by contacting the carbon nanotubes.
The adhesive can be moved away from the tip portion 34 to draw the
carbon nanotubes until the carbon nanotubes are protruding from the
top of the tip portion 34. The tool can be tweezers.
[0067] To form a batch of carbon nanotube micro-tip structures at
one time or an array of carbon nanotube micro-tip structures 300, a
plurality of first hollow patterns 14 can define a plurality of
patterned carbon nanotube film structures 30 arranged in an array,
protruded from the edge of the surface 22 of the insulating
substrate 20 and suspended above the strip-shaped recesses 26.
[0068] To be used in a thermionic emission device or a thermal
field emission device, a cutout can be formed by the laser etching
of the step S3 on the patterned carbon nanotube film structure 30
to increase the resistance at the tip portion 34. The cutout has a
lengthwise direction parallel to the surface 22 of the insulating
substrate 20 and extends along a direction from the edge of the
surface 22 to the tip portion 34.
[0069] The embodiment of the method for making the carbon nanotube
micro-tip structure can further include a step S4 of patterning
on-surface-portion of the carbon nanotube film structure 10 to form
two connecting portions 36 respectively connected to the two
strip-shaped arms 32 in a one to one manner. Applied to the
insulating substrate 20, the carbon nanotube film structure 10 can
have two kinds of portions: the on-surface-portion and the
suspended portion. The on-surface-portion is the portion of the
carbon nanotube film structure 10 located on the surface 22 of the
insulating substrate 20.
[0070] The laser etching is performed on suspended portions of
carbon nanotube film structure to prevent the heat absorption from
the insulating substrate. Therefore, to easily pattern the
on-surface-portion of the carbon nanotube film structure 10, the
step S4 may be processed by different methods.
[0071] Referring to FIG. 14, a method (1) includes a step of
previously laser etching the carbon nanotube film structure 10
before the step S2 of covering the carbon nanotube film structure
10 on the insulating substrate 20 to define a second hollow pattern
16 and the two connecting portions 36 according to the second
hollow pattern 16. In this step, the carbon nanotube film structure
10 can be suspended across a frame during the laser etching.
Therefore, the second hollow pattern 16 of the carbon nanotube film
structure 10 can be easily laser etched. The two connecting
portions 36 defined by the second hollow pattern 16 is located in
the place according to where the two strip-shaped arms 32 will be
formed in the following step S3. After the step S3, the finally
achieved two strip-shaped arms 32 and the two connecting portions
36 are respectively connected. After the step S3, the first hollow
pattern 14 and the second hollow pattern 16 cooperatively define
the patterned carbon nanotube film structure 30 having the
connecting portions 36 and the strip-shaped arms 32. The other
portion of the carbon nanotube film structure 10 is isolated from
the patterned carbon nanotube film structure 30 by the first hollow
pattern 14 and the second hollow pattern 16. An additional step of
removing the other portion of the carbon nanotube film structure 10
can be further included by the method (1), processed by simply
peeling the other portion of the carbon nanotube film structure 10
from the surface 22 of the insulating substrate 20.
[0072] Referring to FIG. 15, a method (2) includes steps of:
previously forming a connecting portion etching groove 28 on the
surface 22 of the insulating substrate 20 before the step S2 of
covering the carbon nanotube film structure 10 on the insulating
substrate 20; and laser etching the portion of the carbon nanotube
film structure 10 suspended above the connecting portion etching
groove 28 after the step S2. The connecting portion etching groove
28 can be a V-shaped groove with a relatively narrow width. The
connecting portion etching groove 28 defines the outline of the two
connecting portions 36 and reaches to the strip-shaped recess 26.
The portion of the carbon nanotube film structure 10 covering the
connecting portion etching groove 28 is suspended above the
connecting portion etching groove 28, thus can be totally etched
out by the laser etching. The patterned carbon nanotube film
structure 30 having the two connecting portions 36 and the two
strip-shaped arms 32 can be isolated from the other portions of the
carbon nanotube film structure 10 by laser etching the portion of
the carbon nanotube film structure 10 suspended above the
connecting portion etching groove 28. Similar to the method (1),
the other portion of the carbon nanotube film structure 10 can be
easily removed from the surface 22 of the insulating substrate
20.
[0073] Referring to FIG. 16, a method (3) includes both the steps
of previously etching the insulating substrate 20 and previously
etching the carbon nanotube film structure 10. The method (3)
includes steps of:
[0074] S41, previously laser etching the carbon nanotube film
structure 10 before the step S2 of covering the carbon nanotube
film structure 10 on the insulating substrate 20 to define a third
hollow pattern 18;
[0075] S42, according to the third hollow pattern 18, previously
forming an assisted etching groove 24 on the surface 22 of the
insulating substrate 20 before the step S2, wherein the assisted
etching groove 24, the third hollow pattern 18, and the
strip-shaped recess 26 cooperatively define the outline of the two
connecting portions 36;
[0076] S43, after the step S2 of covering the carbon nanotube film
structure 10 on the insulating substrate 20, laser etching the
portion of the carbon nanotube film structure 10 suspended above
the assisted etching groove 24, to totally isolate the patterned
carbon nanotube film structure 30 having the two connecting
portions 36 and the two strip-shaped arms 32 from the other
portions of the carbon nanotube film structure 10; and
[0077] S44, removing the other portions of the carbon nanotube film
structure 10 from the surface 22 of the insulating substrate
20.
[0078] The third hollow pattern 18 of the method (3) and the second
hollow pattern 16 of the method (1) of the carbon nanotube film
structure 10 can be formed by the same method. The assisted etching
groove 24 of the method (3) and the connecting portion etching
groove 28 of the method (2) can be formed by the same method.
[0079] In one embodiment, the assisted etching groove 24 includes a
plurality of line-shaped grooves spaced from each other and
parallel to the lengthwise direction of the strip-shaped recesses
26. Each strip-shaped recess 26 has one line-shaped groove located
at one side thereof. The third hollow pattern 18 can be a plurality
of groups of strip-shaped through holes. Each group of strip-shaped
through holes can include three strip-shaped through holes parallel
to and spaced from each other. The length direction of the
strip-shaped through holes can be perpendicular to the line shaped
grooves. The strip-shaped through holes can be located between one
line-shaped groove and one strip-shaped recess. The two ends of the
strip-shaped through holes along the length direction can
respectively reach the line shaped groove and the strip-shaped
recess, to define the outline of the connecting portions 36 and
isolate the connecting portions 36 from the other portions of the
carbon nanotube film structure 10.
[0080] Referring to FIG. 17, a method for forming the assisted
etching groove 24 on the surface 22 of the insulating substrate 20
can include steps of: providing a silicon substrate 50; depositing
a silicon nitride layer 52 on a surface of the silicon substrate
50; patterning the silicon nitride layer 52 through a lithography
method to expose the surface of the silicon substrate 50 that is to
be etched out from the silicon nitride layer 52; treating the
silicon substrate 50 having the patterned silicon nitride layer 52
with a reacting solution (e.g., a KOH solution), to etch the
exposed silicon substrate 50 and form the assisted etching groove
24; and forming a silicon oxide film 54 on the surface of the
silicon substrate 50 by using a plasma-enhanced chemical vapor
deposition method. In one embodiment, the silicon oxide film 54 has
a thickness of about 1 micron, and the assisted etching groove 24
has a V-shaped cross-section. After covering the assisted etching
groove 24 with the carbon nanotube film structure 10, the carbon
nanotube film structure 10 is suspended across the assisted etching
groove 24, and can be etched out by laser etching.
[0081] To facilitate locating the carbon nanotube film structure 10
on the surface 22 of the insulating substrate 20, an additional
step S5 of forming a plurality of location assisted lines 40 can be
further processed. The location assisted lines 40 helps finding the
location of the strip-shaped recesses 26 when covering the carbon
nanotube film structure 10 on the insulating substrate 20, to
arrange the second hollow pattern 16 or the third hollow pattern 18
of the carbon nanotube film structure 10 at a right place according
to the strip-shaped recesses 26. The location assisted lines 40 can
be perpendicular to the lengthwise direction of the strip-shaped
recesses 26. To form an array of carbon nanotube micro-tip
structures, each of the strip-shaped recesses 26 can have a
plurality of location assisted lines 40 formed on a side thereof.
In one embodiment, the plurality of location assisted lines 40 at a
side of one strip-shaped recess 26 are spaced an even distance.
[0082] Referring back to FIG. 13, the method for forming the carbon
nanotube micro-tip structure can further include an additional step
S6 of cutting the insulating substrate 20 to separate the plurality
of patterned carbon nanotube film structures 30, and form a
plurality of carbon nanotube micro-tip structures. In one
embodiment, the insulating substrate 20 having the array of carbon
nanotube micro-tip structures has a size of 25
millimeters.times.26.8 millimeters. After cutting, the insulating
substrate 20 having the single carbon nanotube micro-tip structure
has a size of 3 millimeters.times.4 millimeters.
[0083] The above embodiments of carbon nanotube micro-tip
structures and array of carbon nanotube micro-tip structures can
all be formed by the above method. In some embodiments (e.g., shown
in FIG. 10 and FIG. 11), the carbon nanotube film structure can be
covered on a strip-shaped recess having a wide width and laser
etched to form the carbon nanotube micro-tip structure having the
plurality of tip portions.
[0084] Referring to FIG. 18, to test the joule heating performance,
the two connecting portions of the carbon nanotube micro-tip
structure can be connected between the positive and negative
electrodes of a direct current power source to electrically conduct
the carbon nanotube micro-tip structure in vacuum. In one
embodiment, some other portions of the carbon nanotube film
structure 10 can be kept in the step S44, to electrically connect
the plurality of patterned carbon nanotube film structures 30
together. Specifically, the plurality of patterned carbon nanotube
film structures 30 suspended above the same strip-shaped recess 26
are connected in series, and the plurality of patterned carbon
nanotube film structures 30 suspended above different strip-shaped
recesses 26 are connected in parallel. Referring to FIG. 19, when
the plurality of patterned carbon nanotube film structures 30 are
powered by the direct current power source, the plurality of tip
portions 34 can be illuminated and emit visible lights. Referring
to FIG. 20 and FIG. 21, the carbon nanotube micro-tip structure is
heated during the electrifying. The heating temperature and the
voltage and power of the direct current have a linear relationship.
The carbon nanotube micro-tip structure can be heated to about 1860
K at a voltage of about 13.5 V and a power of about 0.586 mW.
[0085] Referring to FIG. 22, one embodiment of a field emission
election source 510 includes a carbon nanotube micro-tip structure
512. The carbon nanotube micro-tip structure 512 includes an
insulating substrate and a patterned carbon nanotube film
structure. The insulating substrate includes a surface. The surface
has an edge. The patterned carbon nanotube film structure is
partially arranged on the surface of the insulating substrate. The
patterned carbon nanotube film structure includes two strip-shaped
arms. The two strip-shaped arms are joined at one end to form a tip
portion of the patterned carbon nanotube film structure. An angle
.alpha. between the lengthwise directions of the two strip-shaped
arms can be smaller than 180.degree.. The tip portion of the
patterned carbon nanotube film structure protrudes from the edge of
the surface of the insulating substrate and suspended. The
patterned carbon nanotube film structure includes a plurality of
carbon nanotubes parallel to the surface of the insulating
substrate.
[0086] The carbon nanotube micro-tip structure 512 can be the same
as any one of the above embodiments of carbon nanotube micro-tip
structures.
[0087] One embodiment of a field emission device 500 includes the
field emission electron source 510 and an anode electrode 520. The
anode electrode 520 is spaced from and opposite to the field
emission electron source 510. In use, a positive voltage is applied
to the anode electrode 520, a negative voltage is applied to the
carbon nanotube micro-tip structure 512 of the field emission
electron source 510, and electrons are emitted from the tip portion
of the patterned carbon nanotube film structure.
[0088] The field emission device 500 can be a light source or a
displaying device. The anode electrode 520 can include an anode
electrode layer 522 and a fluorescent layer 524 laminated together.
The fluorescent layer 524 faces the tip portion of the patterned
carbon nanotube film structure. The electrons emitted from the tip
portion reach the anode electrode 520 and lighten the fluorescent
layer 524.
[0089] The field emission device 500 can further include a sealing
structure 530 to seal the field emission electron source 510 and
the anode electrode 520 therein in a vacuum. In one embodiment, the
vacuum degree in the sealing structure 530 is about
2.times.10.sup.-5 Pa.
[0090] Referring to FIG. 23, the field emission device 500 is
tested at room temperature and 958K respectively. One embodiment of
the carbon nanotube micro-tip structure can emit an intrinsic field
emission current of about 150 .mu.A. Due to the Joule heating
effect, the field emission current of the carbon nanotube micro-tip
structure at 958K is decreased. Referring to FIG. 24, by
alternating the heating temperatures of the carbon nanotube
micro-tip structure between room temperature and 958K, the field
emission current has a corresponding change. The response speed of
the field emission current change is very fast. Due to the
relatively large resistance of the tip portion of the carbon
nanotube micro-tip structure, the tip portion can be heated at a
high temperature simply by electrifying the carbon nanotube
micro-tip structure. Thus, the carbon nanotube micro-tip structure
has a relatively good thermal field emission performance. Referring
to FIG. 25, the field emission device 500 can have a thermal field
emission by electrifying the carbon nanotube micro-tip structure
while having a voltage difference between the carbon nanotube
micro-tip structure and the anode electrode 520. The field emission
device 500 has a lower turn-on voltage of the field emission at
high temperature than at room temperature. The thermal field
emission current increases with the heating temperature.
[0091] Referring to FIG. 26, an embodiment of an atomic force
microscope probe 600 includes a carbon nanotube micro-tip structure
612. The carbon nanotube micro-tip structure 612 includes an
insulating substrate and a patterned carbon nanotube film
structure. The insulating substrate includes a surface. The surface
has an edge. The patterned carbon nanotube film structure is
partially arranged on the surface of the insulating substrate. The
patterned carbon nanotube film structure includes two strip-shaped
arms. The two strip-shaped arms are joined at one end to form a tip
portion of the patterned carbon nanotube film structure. An angle
.alpha. between the lengthwise directions of the two strip-shaped
arms can be smaller than 180.degree.. The tip portion of the
patterned carbon nanotube film structure protrudes and suspends
from the edge of the surface of the insulating substrate. The
patterned carbon nanotube film structure includes a plurality of
carbon nanotubes parallel to the surface of the insulating
substrate. In use, the tip portion of the patterned carbon nanotube
film structure points towards or parallel to the surface or object
to be observed. The two strip-shaped arms can be used as the
cantilever of the atomic force microscope probe. When the tip
portion of the patterned carbon nanotube film structure approaches
a surface, it is subjected to the influence of attractive or
repulsive forces of chemical, van der Waals, electrostatic, and/or
magnetic nature. By measuring these forces while the tip portion
scans the surface of the object to be observed, it is possible to
reconstitute an image thereof.
[0092] The carbon nanotube micro-tip structure 612 can be the same
as any one of the above embodiments of carbon nanotube micro-tip
structures.
[0093] The carbon nanotube micro-tip structure has a wide use, such
as in a field emission display, SEM, TEM, x-ray tube, electron
momentum spectroscopy, and so on. Further, the carbon nanotube
micro-tip structure has a suspended tip portion which can be used
in an atomic force microscope, transistor, MEMS, and so on.
[0094] It is to be understood that the above description and the
claims drawn to a method may include some indication in reference
to certain steps. However, the indication used is only to be viewed
for identification purposes and not as a suggestion as to an order
for the steps.
[0095] Finally, it is to be understood that the above-described
embodiments are intended to illustrate rather than limit the
disclosure. Variations may be made to the embodiments without
departing from the spirit of the disclosure as claimed. Elements
associated with any of the above embodiments are envisioned to be
associated with any other embodiments. The above-described
embodiments illustrate the scope of the disclosure but do not
restrict the scope of the disclosure.
* * * * *