U.S. patent application number 12/868938 was filed with the patent office on 2010-12-23 for method for making transmission electron microscope micro-grid.
This patent application is currently assigned to TSINGHUA UNIVERSITY. Invention is credited to SHOU-SHAN FAN, CHEN FENG, KAI-LI JIANG, QUN-QING LI, LIANG LIU, LI-NA ZHANG.
Application Number | 20100319833 12/868938 |
Document ID | / |
Family ID | 39792591 |
Filed Date | 2010-12-23 |
United States Patent
Application |
20100319833 |
Kind Code |
A1 |
ZHANG; LI-NA ; et
al. |
December 23, 2010 |
METHOD FOR MAKING TRANSMISSION ELECTRON MICROSCOPE MICRO-GRID
Abstract
A method for making a transmission electron microscope (TEM)
micro-grid includes the following steps. A carbon nanotube film and
a metallic grid are provided. The carbon nantoube film is laid on
the metallic gird. The carbon nanotube film with the metallic gird
is treated with an organic solvent. Wherein, the carbon nanotube
film includes a plurality of carbon nanotube bundles substantially
arranged at the same direction.
Inventors: |
ZHANG; LI-NA; (Beijing,
CN) ; FENG; CHEN; (Beijing, CN) ; LIU;
LIANG; (Beijing, CN) ; JIANG; KAI-LI;
(Beijing, CN) ; LI; QUN-QING; (Beijing, CN)
; FAN; SHOU-SHAN; (Beijing, CN) |
Correspondence
Address: |
Altis Law Group, Inc.;ATTN: Steven Reiss
288 SOUTH MAYO AVENUE
CITY OF INDUSTRY
CA
91789
US
|
Assignee: |
TSINGHUA UNIVERSITY
Beijing
CN
HON HAI PRECISION INDUSTRY CO., LTD.
Tu-Cheng
TW
|
Family ID: |
39792591 |
Appl. No.: |
12/868938 |
Filed: |
August 26, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
12005741 |
Dec 28, 2007 |
|
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|
12868938 |
|
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Current U.S.
Class: |
156/77 ;
156/305 |
Current CPC
Class: |
Y10T 29/49002 20150115;
H01J 37/20 20130101; H01J 37/26 20130101 |
Class at
Publication: |
156/77 ;
156/305 |
International
Class: |
B32B 37/16 20060101
B32B037/16; B29C 65/00 20060101 B29C065/00 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 30, 2007 |
CN |
200710073768.1 |
Claims
1. A method for making a transmission electron microscope
micro-grid, the method comprising: (a) providing a carbon nanotube
film and a metallic grid; (b) laying the carbon nanotube film on
the metallic grid; and (c) treating the carbon nanotube film on the
metallic with an organic solvent.
2. The method as claimed in claim 1, wherein step (a) comprises the
steps of: (a1) providing an array of carbon nantoubes; and (a2)
drawing the carbon nanotube film from the array of carbon
nantoubes.
3. The method as claimed in claim 2, wherein the array of carbon
nanotubes is a super-aligned array of carbon nanotubes, and the
super-aligned array of carbon nanotubes is made by the steps of:
(a11) providing a substantially flat and smooth substrate; (a12)
forming a catalyst layer on the substrate; (a13) annealing the
substrate with the catalyst layer in air at a temperature in an
approximate range from 700.degree. C. to 900.degree. C. for about
30 to 90 minutes; (a14) heating the substrate with the catalyst
layer at a temperature in an approximate range from 500.degree. C.
to 740.degree. C. in a furnace with a protective gas therein; and
(a15) supplying a carbon source gas to the furnace for about 5 to
30 minutes.
4. The method as claimed in claim 1, wherein a material of the
metallic grid comprises copper or nickel.
5. The method as claimed in claim 2, wherein step (a2) further
comprises: (a21) selecting a plurality of carbon nanotube segments
having a predetermined width from the array of carbon nanotubes;
and (a22) pulling the plurality of carbon nanotube segments at a
uniform speed.
6. The method as claimed in claim 5, wherein the carbon nanotube
film comprises a plurality of carbon nanotubes substantially
parallel to a pulling direction.
7. The method as claimed in claim 1, wherein step (c) further
comprises dropping the organic solvent from a dropper to an entire
surface of the carbon nanotube film to make a compact structure
between the carbon nanotube film and the metallic grid.
8. The method as claimed in claim 1, wherein step (c) further
comprises immersing the metallic grid with the carbon nanotube film
thereon into a container having the organic solvent therein, to
make a compact structure between the carbon nanotube film and the
metallic grid.
9. The method as claimed in claim 1, wherein the organic solvent
comprises of a material that is selected from the group consisting
of ethanol, methanol, acetone, dichloroethane, and chloroform.
10. The method as claimed in claim 1, further comprising a step of
removing extra portions of the carbon nanotube film on edges of the
metallic grid.
11. A method for making a transmission electron microscope
micro-grid, the method comprising: (a) providing a plurality of
carbon nanotube films and a metallic grid; (b) laying the plurality
of carbon nanotube films on the metallic grid; and (c) treating the
plurality of carbon nanotube films on the metallic grid with an
organic solvent.
12. The method as claimed in claim 11, wherein each of the
plurality of carbon nanotube films comprises a plurality of carbon
nanotubes substantially arranged along an aligned direction.
13. The method as claimed in claim 12, wherein the plurality of
carbon nanotube films laid one after another to form a multi-layer
carbon nanotube film structure.
14. The method as claimed in claim 13, wherein the plurality of
carbon nanotube films are stacked to form a microporous
structure.
15. The method as claimed in claim 11, wherein step (c) further
comprises dropping the organic solvent from a dropper to an entire
surface of the plurality of carbon nanotube films.
16. The method as claimed in claim 11, wherein step (c) is further
comprises immersing the metallic grid with the plurality of carbon
nanotube films thereon into a container having the organic solvent
therein.
17. A method for making a transmission electron microscope
micro-grid, the method comprising: (a) providing a first carbon
nanotube film comprising a plurality of carbon nanotubes arranged
along a first direction, a second carbon nanotube film comprising a
plurality of carbon nanotubes arranged along a second direction,
and a metallic grid; (b) laying the first carbon nanotube film on
the metallic grid; (c) adhering the second carbon nanotube film on
the first carbon nanotube film to form a stacked multi-layer carbon
nanotube film; and (d) treating the stacked multi-layer carbon
nanotube film on the metallic with an organic solvent.
18. The method as claimed in claim 17, wherein in step (c) the
second carbon nanotube film is adhered on the first carbon nanotube
film along such that an angle between the first direction and the
second direction is about 90.degree..
19. The method as claimed in claim 17, wherein step (d) further
comprises dropping the organic solvent from a dropper to soak an
entire surface of the stacked multi-layer carbon nanotube film with
the organic solvent.
20. The method as claimed in claim 17, wherein step (d) further
comprises immersing the metallic grid with the stacked multi-layer
carbon nanotube film thereon into a container having the organic
solvent therein.
Description
RELATED APPLICATIONS
[0001] This application is a divisional application of U.S. patent
application, entitled "TRANSMISSION ELECTRON MICROSCOPE MICRO-GRID
AND METHOD FOR MAKING THE SAME" with application Ser. No.
12/005,741, filed on Dec. 28, 2007. U.S. patent application Ser.
No. 12/005,741, claims the benefit of priority under 35U.S.C. 119
from Chinese Patent Application 200710073768.1 filed on Mar. 30,
2007 in the China Intellectual Property Office, disclosure of which
is incorporated herein by reference.
BACKGROUND
[0002] 1. Technical Field
[0003] The present invention relates to a method for making a
transmission electron microscope (TEM) micro-grid.
[0004] 2. Discussion of Related Art
[0005] In a transmission electron microscope (TEM), a porous carbon
supporting film (i.e., micro-grid) is used, as an important tool,
to carry powder samples and to observe high-resolution transmission
electron microscope (HRTEM) images. With the development of
nano-technology, micro-grids are increasingly coming into
widespread use in the field of electron microscopy. Recently, the
micro-grids used in transmission electron microscopes are usually
manufactured using a layer of organic porous membrane covered on a
metal mesh net, such as copper mesh net, or nickel mesh net, and
subsequently a layer of non-crystal carbon films are deposited
thereon via evaporation.
[0006] However, in actual applications, the non-crystal carbon
films influence the observation of the high-resolution transmission
electron microscopy images significantly, particularly when the
diameter of the observed particles is less than 5 nanometers.
[0007] What is needed, therefore, is a transmission electron
microscope (TEM) micro-grid and method for making the same, and the
TEM micro-grids are conducive to acquiring better high-resolution
transmission electron microscopy images when the diameter of the
observed particles is less than 5 nanometers.
SUMMARY
[0008] In one embodiment, a method for making a TEM micro-grid
includes the steps of: (a) providing an array of carbon nanotubes;
(b) drawing a carbon nanotube film from the array of carbon
nanotubes; (c) covering at least one above-described carbon
nanotube film on a metallic grid and treating the at least one
carbon nanotube film with an organic solvent.
[0009] Other advantages and novel features of the present TEM
micro-grid will become more apparent from the following detailed
description of preferred embodiments when taken in conjunction with
the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] Many aspects of the embodiments can be better understood
with references to the following drawings. The components in the
drawings are not necessarily drawn to scale, the emphasis instead
being placed upon clearly illustrating the principles of the
embodiments. Moreover, in the drawings, like reference numerals
designate corresponding parts throughout the several views.
[0011] FIG. 1 is a flow chart of a method for making a TEM
micro-grid, in accordance with a present embodiment.
[0012] FIG. 2 is a structural schematic of a TEM micro-grid.
[0013] FIG. 3 shows a Scanning Electron Microscope (SEM) image of a
TEM micro-grid, in accordance with a present embodiment;
[0014] FIG. 4 shows a Scanning Electron Microscope (SEM) image of a
carbon nanotube film of the TEM micro-grid, in accordance with a
present embodiment;
[0015] FIG. 5 shows a Transmission Electron Microscope (TEM) image
of gold nano-particles observed by a TEM adopting a TEM micro-grid
in accordance with the present embodiment.
[0016] FIG. 6 is similar to FIG. 5 but greatly magnified.
[0017] Corresponding reference characters indicate corresponding
parts throughout the several views. The exemplifications set out
herein illustrate at least one preferred embodiment of the present
TEM micro-grid, in at least one form, and such exemplifications are
not to be construed as limiting the scope of the invention in any
manner.
DETAILED DESCRIPTION
[0018] Reference will now be made to the drawings to describe, in
detail, embodiments of the present TEM micro-grid and method for
making the same.
[0019] Referring to FIG. 1, a method for making a TEM micro-grid
includes the steps of: (a) providing an array of carbon nanotubes,
quite suitably, providing a super-aligned array of carbon
nanotubes; (b) drawing a carbon nanotube film from the array of
carbon nanotubes; (c) covering at least one above-described carbon
nanotube film on a metallic grid, and treating the at least one
carbon nanotube film with an organic solvent.
[0020] In step (a), a given super-aligned array of carbon nanotubes
can be formed by the steps of: (a1) providing a substantially flat
and smooth substrate; (a2) forming a catalyst layer on the
substrate; (a3) annealing the substrate with the catalyst layer
thereon in air at a temperature in an approximate range from
700.degree. C. to 900.degree. C. for about 30 to 90 minutes; (a4)
heating the substrate with the catalyst layer thereon at a
temperature in an approximate range from 500.degree. C. to
740.degree. C. in a furnace with a protective gas therein; and (a5)
supplying a carbon source gas to the furnace for about 5 to 30
minutes and growing a super-aligned array of carbon nanotubes on
the substrate.
[0021] In step (a1), the substrate can be a P-type silicon wafer,
an N-type silicon wafer, or a silicon wafer with a film of silicon
dioxide thereon. Preferably, a 4 inch P-type silicon wafer is used
as the substrate. In step (a2), the catalyst can, advantageously,
be made of iron (Fe), cobalt (Co), nickel (Ni), or any alloy
thereof.
[0022] In step (a4), the protective gas can, beneficially, be made
up of at least one of nitrogen (N.sub.2), ammonia (NH.sub.3), and a
noble gas. In step (a5), the carbon source gas can be a hydrocarbon
gas, such as ethylene (C.sub.2H.sub.4), methane (CH.sub.4),
acetylene (C.sub.2H.sub.2), ethane (C.sub.2H.sub.6), or any
combination thereof.
[0023] The super-aligned array of carbon nanotubes can,
opportunely, have a height of about 200 to 400 microns and includes
a plurality of carbon nanotubes parallel to each other and
approximately perpendicular to the substrate. The super-aligned
array of carbon nanotubes formed under the above conditions is
essentially free of impurities, such as carbonaceous or residual
catalyst particles. The carbon nanotubes in the super-aligned array
are closely packed together by the van der Waals attractive
force.
[0024] Step (b) further includes the substeps of: (b1) selecting a
plurality of carbon nanotube segments having a predetermined width
from the array of carbon nanotubes; (b2) pulling the carbon
nanotube segments at an even/uniform speed to form the carbon
nanotube film.
[0025] In step (b1), quite usefully, the carbon nanotube segments,
having a predetermined width, can be selected by using an adhesive
tape as a tool to contact the super-aligned array. In step (b2),
the pulling direction is, usefully, substantially perpendicular to
the growing direction of the super-aligned array of carbon
nanotubes.
[0026] More specifically, during the pulling process, as the
initial carbon nanotube segments are drawn out, other carbon
nanotube segments are also drawn out end to end, due to the van der
Waals attractive force between the ends of adjacent segments. The
carbon nanotube film produced in such manner can be selectively
formed having a predetermined width. The carbon nanotube film
includes a plurality of carbon nanotube segments. The carbon
nanotubes in the carbon nanotube film are mainly parallel to the
pulling direction of the carbon nanotube film.
[0027] A width of the carbon nanotube film depends on a size of the
carbon nanotube array. A length of the carbon nanotube film can be
arbitrarily set as desired. In one useful embodiment, when the
substrate is a 4 inch type wafer as in the present embodiment, a
width of the carbon nanotube film is in an approximate range from 1
centimeter to 10 centimeters.
[0028] It is noted that because the carbon nanotubes in the
super-aligned carbon nanotube array have a high purity and a high
specific surface area, the carbon nanotube film is adhesive. As
such, the carbon nanotube film can be adhered to the surface of the
substrate directly and a plurality of carbon nanotube films can be
adhered to a surface one after another to form a multi-layer carbon
nanotube film structure. The number of the layers is arbitrary and
depends on the actual needs/use. The adjacent layers of the carbon
nanotube film are combined by van de Waals attractive force to form
a stable multi-layer film.
[0029] Quite usefully, the carbon nanotube film can be treated with
an organic solvent. The organic solvent is volatilizable and can be
selected from the group consisting of ethanol, methanol, acetone,
dichloroethane, chloroform, and combinations thereof. Quite
suitably, the organic solvent is ethanol in the present embodiment.
The carbon nanotube film structure can, beneficially, be treated by
either of two methods: dropping the organic solvent from a dropper
to soak the entire surface of side carbon nanotube film structure
or immerging a frame with the carbon nanotube film structure
thereon into a container having an organic solvent therein. After
being soaked by the organic solvent, the carbon nanotube segments
in the carbon nanotube film will at least partially compact/shrink
into carbon nanotube bundles due to the surface tension created by
the organic solvent. Due to the decrease of the surface via
bundling, the coefficient of friction of the carbon nanotube film
is reduced, but the carbon nanotube film maintains high mechanical
strength and toughness. Further, due to the shrinking/compacting of
the carbon nanotube segments into the carbon nanotube bundles, the
parallel carbon nanotube bundles are, relatively, distant
(especially compared to the initial layout of the carbon nanotube
segments) to each other in one layer and cross with the parallel
carbon nanotube bundles in each adjacent layer. As such, a carbon
nanotube film having a microporous structure can thus be formed
(i.e., the micropores are defined by the spacing/gaps between
adjacent bundles). The resulting spacing can, beneficially, be
about in a range of 100-500 mesh.
[0030] It is to be understood that the microporous structure is
related to the number of the layers of the carbon nanotube film
structure. The greater the number of layers that are formed in the
carbon nanotube film structure, the greater the number of bundles
in the carbon nanotube film structure will be. Accordingly, the
spacing/gaps between adjacent bundles and the diameter of the
micropores will decrease. Further, a carbon nanotube film structure
of arbitrarily chosen width and length can be formed by piling a
plurality of carbon nanotube films and partially overlapped with
each other. The width and length of the carbon nanotube film
structure are not confined by the width and the length of the
carbon nanotube film pulled from the array of carbon nanotubes.
[0031] Step (c) can be executed as follows: (c1) treating at least
one carbon nanotube film achieved by step (b) with an organic
solvent; and (c2) covering the at least one carbon nanotube film on
a metallic grid. In step (c), the material of the metallic grid is
copper or other metal material. The organic solvent is
volatilizable and can be selected from the group consisting of
ethanol, methanol, acetone, dichloroethane, chloroform, and
combinations thereof. The organic solvent can be dropped from a
dropper, directly, to soak the entire surface of side carbon
nanotube film structure to make a compact structure between the
carbon nanotube film structure and the metallic grid. After step
(c), a step of removing extra portions of the carbon nanotube film
on edges of the metallic grid is further provided.
[0032] It can be understood that the TEM micro-grid can be made by
a carbon nanotube film drawn from an array of carbon nanotubes
covered, directly, on a metallic grid and a plurality of the carbon
nanotube films can be adhered on the metallic grid with carbon
nanotube films thereon in sequence and parallel to each other. And
then, an organic solvent is used to treat the carbon nanotube films
to acquire a TEM micro-grid structure.
[0033] Referring to FIG. 2 and FIG. 3, a TEM micro-grid 20 adopting
a carbon nanotube film structure 24, formed by the method described
above, is shown. The TEM micro-grid 20 includes a metallic grid 22
and a carbon nanotube film structure 24 covered thereon. The carbon
nanotube film structure 24 includes at least one layer of carbon
nanotube film. Beneficially, the carbon nanotube film structure 24
is formed by a plurality of carbon nanotube films overlapped or
stacked with each other. The number of the layers and the angle
between the aligned directions of two adjacent layers may be
arbitrarily set as desired. A diameter of the microporous structure
relates to the layers of the carbon nanotube film and is in an
approximate range from 1 nanometer to 10 micrometers.
[0034] Referring to FIG. 4, a Scanning Electron Microscope (SEM)
image of the TEM micro-grid adopting multi-layer carbon nanotube
films is shown. The angle between the aligned directions of the
stacked multi-layer carbon nanotube film is 90.degree.. The
adjacent layers of the carbon nanotube film are combined by van de
Waals attractive force to form a stable multi-layer film. The
carbon nanotubes in the carbon nanotube film are aligned. The
carbon nanotube film includes a plurality of carbon nanotube
bundles in a preferred orientation. Bundles in two adjacent layers
are crossed with each other to form a microporous structure. A
diameter of the micropores is in an approximate range from 1
nanometer to 10 micrometers.
[0035] The small sizes of the micropores in the microporous
structure of the present embodiment can be used to support
nano-materials, such as nano-particles, nano-wires, nano-rods, for
the observation thereof via TEM. When the size of the
nano-particles is less than 5 nanometers, the effect of the
micropores is not obvious, but the adsorption effect of carbon
nanotubes plays a main role. Those nano-particles with small size
can be adsorbed stably on the walls of the carbon nanotubes and can
be observed. Referring to FIG. 5 and FIG. 6, the black particles
are gold nano-particles to be observed. The gold nano-particles are
adsorbed stably on the walls of the carbon nanotubes and that is
conducive to the observation of high-resolution image of gold
nano-particles.
[0036] In addition, since the carbon nanotubes in the carbon
nanotube array are of high-purity, uniform size, and have less
defects, the TEM micro-grid of the present embodiment interference
to the morphology and structure of the samples to be observed and
the high-resolution image of the nano-particles adsorbed on the
carbon nanotubes is minimized.
[0037] Compared to the conventional TEM micro-grid and method for
making the same, the TEM micro-grid in the present embodiment can
be formed by a carbon nanotube film drawn from an array of carbon
nanotubes covered, directly, on a metallic grid and the method is
simple, fast and conducive to large-scale production. The TEM
micro-grid made by the present method has stable properties. What's
more, the absorption property of the carbon nanotubes is conducive
to observation of high-resolution TEM image of nano-particles with
a size of less than 5 nanometers.
[0038] Finally, it is to be understood that the above-described
embodiments are intended to illustrate rather than limit the
invention. Variations may be made to the embodiments without
departing from the spirit of the invention as claimed. The
above-described embodiments illustrate the scope of the invention
but do not restrict the scope of the invention.
* * * * *