U.S. patent application number 11/432995 was filed with the patent office on 2007-04-26 for metal nanowire array and method for fabricating the same.
This patent application is currently assigned to HON HAI Precision Industry CO., LTD.. Invention is credited to Tsai-Shih Tung.
Application Number | 20070089564 11/432995 |
Document ID | / |
Family ID | 37984108 |
Filed Date | 2007-04-26 |
United States Patent
Application |
20070089564 |
Kind Code |
A1 |
Tung; Tsai-Shih |
April 26, 2007 |
Metal nanowire array and method for fabricating the same
Abstract
A method for fabricating a metal nanowire array (30) includes
the following steps: providing a carbon nanotube array (10) which
includes a number of carbon nanotubes (14), immersing the carbon
nanotube array in a colloidal solution (20) which contains a
solvent (22) and a number of metal nanocrystals (24) dispersed in
the solvent so as to self-assemble the metal nanocrystals on
exterior surfaces of the carbon nanotubes; taking the carbon
nanotube array out of the colloidal solution; and heating the metal
nanocrystals on the surfaces of the carbon nanotubes in a manner
such that the metal nanocrystals are fused into a metal nanowire
array.
Inventors: |
Tung; Tsai-Shih; (Tu-Cheng,
TW) |
Correspondence
Address: |
PCE INDUSTRY, INC.;ATT. CHENG-JU CHIANG JEFFREY T. KNAPP
458 E. LAMBERT ROAD
FULLERTON
CA
92835
US
|
Assignee: |
HON HAI Precision Industry CO.,
LTD.
Tu-Cheng City
TW
|
Family ID: |
37984108 |
Appl. No.: |
11/432995 |
Filed: |
May 12, 2006 |
Current U.S.
Class: |
75/370 |
Current CPC
Class: |
C30B 5/00 20130101; B22F
2998/10 20130101; H01L 2221/1094 20130101; C30B 29/04 20130101;
B22F 1/025 20130101; C30B 29/60 20130101; B82Y 30/00 20130101; B22F
1/0025 20130101; C30B 29/02 20130101; B22F 2998/10 20130101; C01B
32/00 20170801; B22F 1/0018 20130101; B22F 1/025 20130101; B22F
1/0025 20130101 |
Class at
Publication: |
075/370 |
International
Class: |
B22F 9/24 20060101
B22F009/24 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 20, 2005 |
CN |
200510100544.6 |
Claims
1. A method for fabricating a metal nanowire array, comprising the
steps of providing a carbon nanotube array comprising a plurality
of carbon nanotubes; immersing the carbon nanotube array in a
colloidal solution containing a solvent and a plurality of metal
nanocrystals dispersed therein, thereby the metal nanocrystals
being self-assembled on exterior surfaces of the carbon nanotubes;
taking the carbon nanotube array out of the colloidal solution; and
heating the metal nanocrystals in a manner such that the metal
nanocrystals are fused into the metal nanowire array.
2. The method as claimed in claim 1, wherein the metal nanocrystals
is comprised of a material selected from the group consisting of
gold, silver, copper, tin, nickel, and germanium.
3. The method as claimed in claim 1, wherein the solvent is
selected from the group consisting of water, chloroform, hexylene
glycol and alcohols containing less than 5 carbon atoms.
4. The method as claimed in claim 1, wherein the colloidal solution
furthermore contains a stabilizer agent.
5. The method as claimed in claim 4, wherein the stabilizer agent
is selected from the group consisting of tetraoctylzrnmonium
bromide, sodium citrate, and poly sodium 4-styrensnlfonate.
6. The method as claimed in claim 1, wherein the carbon nanotube
array is immersed in the colloidal solution for a time period in
the range from 5 to 72 hours.
7. The method as claimed in claim 1, wherein the metal nanocrystals
are heated to a temperature that is equal to or higher than a
melting point of the metal nanocrystals.
8. The method as claimed in claim 7, wherein the metal nanocrystals
are heated for a time period in the range from 35 to 60
seconds.
9. The method as claimed in claim 7, wherein the carbon nanotubes
extend in a common direction.
10. A metal nanowire array comprising: an array of metal nanowires
extending in a common direction, each metal nanowire comprising a
core portion comprised of at least one carbon nanotube, and a
cladding portion enclosing the core portion therein, the cladding
portion being comprised of metal polycrystalline.
11. A metal nanowire array as claimed in claim 10, wherein the
metal polycrystalline is comprised of a material selected from the
group consisting of gold, silver, copper, nickel, and germanium.
Description
BACKGROUND
[0001] 1. Technical Field
[0002] The present invention relates generally to nanomaterials,
and more particularly to a metal nanowire array and a method for
fabricating the same.
[0003] 2. Discussion of Related Art
[0004] Miniaturization of integrated circuits is necessary for
meeting the demand of processing data at higher speeds. Although
some existing photolithography based technologies are useful in
miniaturization, it is generally recognized that the existing
technologies will reach their fundamental limits in the near future
because of the wavelengths of the light sources used.
[0005] An alternative technology is the "bottom-up" assembly of
integrated arrays of nanometer-scaled circuits from metal and
semiconductor nanocrystals. In respect of this alternative
technology, three key objectives must be accomplished. The first is
the self-assembly of nanometer-scaled structures from nanocrystals
dispersed in colloidal solution. The second is the
self-organization of these structures on technologically relevant
substrates. The third is the processing of these organized
nanocrystal assemblies into robust structures suitable for
practical applications.
[0006] In recent years, some exciting progress toward the first and
second objects has been made. However, relatively little progress
has been reported in the third area. Accordingly, a metal nanowire
array with a robust structure suitable for practical applications
and a method of fabricating such a metal nanowire array are
desired.
SUMMARY
[0007] In one embodiment, a metal nanowire array includes an array
of metal nanowires extending in a common direction, each metal
nanowire including a core portion containing at least one carbon
nanotube, and a cladding portion enclosing the core portion therein
which includes metal polycrystalline.
[0008] In another embodiment, a method for fabricating a metal
nanowire array includes the following steps: providing a carbon
nanotube array which includes a number of carbon nanotubes;
immersing the carbon nanotube array in a colloidal solution which
contains a solvent and a number of metal nanocrystals dispersed in
the solvent for self-assembling the metal nanocrystals on exterior
surfaces of the carbon nanotubes; taking the carbon nanotube array
out of the colloidal solution; and heating the metal nanocrystals
on the surfaces of the carbon nanotubes in a manner such that the
metal nanocrystals are fused into the metal nanowire array.
[0009] This and other features and advantages of the present
invention as well as the preferred embodiments thereof and a metal
nanowire array and techniques for fabricating metal nanowire array
in accordance with the invention will become apparent from the
following detailed description and the descriptions of the
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] Many aspects of the present metal nanowire array and related
manufacture method can be better understood with reference 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 present method.
Moreover, in the drawings, like reference numerals designate
corresponding parts throughout the several views
[0011] FIG. 1 is a cross sectional schematic view of a metal
nanowire array in accordance with the preferred embodiment;
[0012] FIG. 2 is a flow chart of a method for fabricating a metal
nanowire array in accordance with the preferred embodiment; and
[0013] FIGS. 3A-3D are schematic views showing successive stages of
the method for fabricating a metal nanowire array in accordance
with the preferred embodiment.
DETAILED DESCRIPTION 0F PREFERRED EMBODIMENTS
[0014] Referring now to FIG. 1, a metal nanowire array 100 in
accordance with the preferred embodiment includes a substrate 110
and an array of metal nanowires 120 extending in a substantially
common direction. Each of the metal nanowires 120 includes a core
portion 122 and a cladding portion 124. The core potion 122 is
enclosed in the cladding portion 124. It should be noted that the
cladding portion 124 could be partially or entirely formed
on/enclosing an exterior surface of the core portion 122 and which
should be considered to be within the scope of the present
invention. The core portion 122 may include a single carbon
nanotube or a plurality of bundled carbon nanotubes. The carbon
nanotubes may be formed on the substrate 110. The cladding portion
124 includes metal polycrystalline, the metal can be selected from
the group consisting of gold, silver, copper, tin, nickel, and
germanium. Because of the strength of the aligned structure of the
metal nanowire array 100, it is suitable for practical
applications. The metal nanowire array 100 can be fabricated by the
following method:
[0015] Referring now to FIG. 2, a method in accordance with the
preferred embodiment includes the steps (in no particular order)
of:
[0016] step 210: providing a carbon nanotube array 10 which
includes a number of carbon nanotubes 14;
[0017] step 220: immersing the carbon nanotube array 10 in a
colloidal solution 20 of metal nanocrystals 24 for self-assembling
the metal nanocrystals 24 on exterior surfaces of the carbon
nanotubes 14;
[0018] step 230: taking the carbon nanotube array 10 out of the
colloidal solution 20; and
[0019] step 240: heating the metal nanocrystals assembled on
exterior surfaces of the carbon nanotubes 14 to form a continuous
polycrystalline metal nanowire array 40.
[0020] In step 210, referring to FIG. 3A, the carbon nanotube array
10 includes a substrate 12 and a number of carbon nanotubes 14
formed on the substrate 12. The carbon nanotubes 14 extend in a
common direction, e.g. perpendicularly from the substrate. A method
for preparing such a carbon nanotube array with well-aligned carbon
nanotubes is disclosed, for example, in US patent 20040053053A1 by
Jiang, KaiLi. et al, which is incorporated herein by reference. The
method includes the following steps: providing a smooth substrate;
depositing a metal catalyst layer on a surface of the substrate;
heating the treated substrate to a predetermined temperature in
flowing protective gas; and introducing a mixture of carbon source
gas and protective gas for 5-30 minutes, thus forming a carbon
nanotube array extending from the substrate. A patterned carbon
nanotube array can be prepared by forming a patterned catalyst
layer.
[0021] In step 220, referring to FIG. 3B, the carbon nanotube array
10 is immersed into a colloidal solution 20 of a metal nanocrystals
for a period of time. The colloidal solution 20 contains a solvent
22 and a number of metal nanocrystals 24 dispersed in the solvent
22. The solvent 22 can be selected from the group consisting of
water, chloroform, hexylene glycol, and alcohols containing a
number of less than 5 carbon atoms (i.e. methanol, ethanol,
propanol and butanol). The particle size of the metal nanocrystals
24 is in the range from 1 nanometer to 100 nanometers. The metal
nanocrystals can be chosen from the group consisting of gold,
silver, copper, tin, nickel, and germanium. Preferably the
colloidal solution 20 further contains a stabilizer agent, the
stabilizer can be selected for the group consisting of: tetraoctyl
ammonium bromide, sodium citrate and poly sodium 4-styrene
sulphonate. In this step, the metal nanocrystals 24 are
self-assembled on partial or entire exterior surfaces of the carbon
nanotubes 14. Preferably, the metal nanocrystals 24 are
self-assembled on entire exterior surfaces of the carbon nanotubes
14. The carbon nanotube array 10 is immersed in the colloidal
solution for a time period in the range from 5 to 72 hours,
preferably 10 to 30 hours.
[0022] In step 230, the carbon nanotube array 10 is taken out of
the colloidal solution 20. Referring to FIG. 3C, after the previous
self-assembly step, the metal nanocrystals 24 are attached to
exterior surfaces of the carbon nanotubes 14. The metal
nanocrystals 24 are independent from each other as
sub-monolayer/monolayer at exterior surfaces of the carbon
nanotubes 14 fitted to a Langmuir isotherm.
[0023] In step 240, the metal nanocrystals 24 attached to exterior
surfaces of the carbon nanotubes 14 is heated to a temperature in
air for a period of time to form a continuous polycrystalline metal
nanowire array. The temperature is equal to or higher than the
melting point of the metal nanocrystals. It should be noted that
the metal nanocrystals have a melting point lower than bulk metal.
Furthermore, surface melting can occur at a lower temperature due
to enhanced mobility of metal atoms. For example, the gold
nanocrystals attached to the surface of the carbon nanotubes 14
have a melting point of about 300 degree Celsius. Preferably, the
metal nanocrystals 24 are heated for a time period in the range for
example from 35 to 60 seconds as in the illustrated embodiment.
Referring to FIG. 3D, after the heating step, the neighboring
spherical metal nanocrystals are fused together, therefore a
polycrystalline metal nanowire array 40 composed of a number of
nanowires 30 each having a nanotube core is formed.
[0024] It is known that well-aligned carbon nanotube arrays can be
obtained by various methods. Therefore, according to the present
embodiment, metal nanowire arrays can be synthesized with the
nanotube template. The metal nanowire array is suitable for
practical applications, such as sensor, catalyst, and thermal
interference material.
[0025] 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.
* * * * *