U.S. patent application number 12/217757 was filed with the patent office on 2009-01-15 for binary alloy single-crystalline metal nanostructures and fabrication method thereof.
Invention is credited to June Ho In, Bong Soo Kim, Krishna Kumar, Hyo Tcheri Lhee, Yeong Dong Yoo.
Application Number | 20090013824 12/217757 |
Document ID | / |
Family ID | 40176078 |
Filed Date | 2009-01-15 |
United States Patent
Application |
20090013824 |
Kind Code |
A1 |
Kim; Bong Soo ; et
al. |
January 15, 2009 |
Binary alloy single-crystalline metal nanostructures and
fabrication method thereof
Abstract
Disclosed are a method of fabricating a binary alloy
nanostructure by using metal oxides, metal substances or metal
halides of metal elements used to form a binary alloy and/or binary
alloy substances as a precursor through a vapor phase synthesis
method and a binary alloy nanostructure fabricated by the same.
More particularly, the present invention provides a method of
fabricating a binary alloy nanowire or nanobelt which comprises
placing a precursor on the front part of a reaction furnace and a
substrate on the rear part of the furnace, and heat treating both
of them under inert gas atmosphere to produce the nanowire or
nanobelt and, in addition, a binary alloy nanowire or nanobelt
fabricated by the method according to the present invention.
Inventors: |
Kim; Bong Soo; (Daejeon,
KR) ; In; June Ho; (Daejeon, KR) ; Kumar;
Krishna; (Daejeon, KR) ; Lhee; Hyo Tcheri;
(Daejeon, KR) ; Yoo; Yeong Dong; (Daejeon,
KR) |
Correspondence
Address: |
TIPS GROUP;c/o Intellevate LLC
P. O. BOX 52050
Minneapolis
MN
52050
US
|
Family ID: |
40176078 |
Appl. No.: |
12/217757 |
Filed: |
July 7, 2008 |
Current U.S.
Class: |
75/255 ; 75/351;
977/810; 977/900 |
Current CPC
Class: |
C30B 25/02 20130101;
C30B 29/52 20130101; C30B 29/62 20130101 |
Class at
Publication: |
75/255 ; 75/351;
977/810; 977/900 |
International
Class: |
B22F 1/00 20060101
B22F001/00; B22F 9/00 20060101 B22F009/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 9, 2007 |
KR |
10-2007-0068548 |
Claims
1. A method of fabricating a binary alloy single-crystalline metal
nanostructure, comprising: using two substances selected from a
first material to a third material separately or in a combination
thereof as a precursor; and heat treating the precursor as well as
a semiconductor or insulator single-crystalline substrate under
inert atmosphere after placing the precursor on front part of a
reaction furnace and the single-crystalline substrate on rear part
of the reaction furnace to fabricate a binary alloy
single-crystalline metal nanowire or nanobelt, wherein the binary
alloy for the nanostructure includes the first material containing
metal oxides, metal substances or metal halides of a metal used to
form the binary alloy, a second material containing metal oxides,
metal substances or metal halides of another metal used to form the
binary alloy, and/or the third material containing any one of
binary alloy substances for the binary alloy.
2. The method according to claim 1, wherein the precursor includes
a mixture of the first material and the second material, a mixture
of the first material and the third material, or the third material
alone.
3. The method according to claim 1, wherein metal halides of the
first material or the second material are selected from a group
consisting of metal fluoride, metal chloride, metal bromide and
metal iodide.
4. The method according to claim 1, wherein the inert gas flow is
introduced through the front part to the rear part of the furnace
at 10 to 600 sccm.
5. The method according to claim 1, wherein heat treatment is
conducted under pressure ranging from 2 to 30 torr.
6. The method according to claim 1, wherein the precursor is
maintained at 500 to 1200.degree. C. while the single-crystalline
substrate is maintained at 700 to 1100.degree. C.
7. The method according to claim 1, wherein the precursor is
maintained at 500 to 1200.degree. C. while the single-crystalline
substrate is maintained at 100 to 200.degree. C.
8. The method according to claim 1, wherein the precursor is a
mixture containing metal halides of the first material as well as
the second material, and metal halides of the first material and
the second material are physically separate from each other and
positioned at the front part of the reaction furnace.
9. The method according to claim 1, wherein metal halides of the
first material are maintained at 500 to 800.degree. C. and the
second material is maintained at 800 to 1200.degree. C., while the
single-crystalline substrate is maintained at 700 to 1100.degree.
C.
10. The method according to claim 1, wherein metal oxides of the
first material or the second material are selected from a group
consisting of silver oxide, gold oxide, cobalt oxide, palladium
oxide and tellurium oxide.
11. The method according to claim 1, wherein metal substances of
the first material or the second material are selected from a group
consisting of silver, gold, cobalt, palladium and tellurium in
terms of metal element.
12. The method according to claim 1, wherein metal halides of the
first material or the second material are selected from a group
consisting of silver halide, gold halide, cobalt halide, palladium
halide and tellurium halide.
13. The method according to claim 1, wherein binary alloy
substances of the third material include Pd and Au alloy, Co and Ag
alloy, Ag and Te alloy, or Bi and Te alloy.
14. The method according to claim 1, wherein the binary alloy
single-crystalline metal nanowire formed on the single-crystalline
substrate is selected from a Pd.sub.xAu.sub.1-x
(0.01.ltoreq.x.ltoreq.0.99) single-crystalline metal nanowire, a
Co.sub.yAg.sub.1-y (0.01.ltoreq.x.ltoreq.0.5) single-crystalline
metal nanowire, a Ag.sub.2Te single-crystalline metal nanowire and
a Bi.sub.1Te.sub.1 single-crystalline metal nanobelt.
15. A binary alloy nanostructure comprising a solid solution of
single crystals of two metal elements or a compound of the single
crystals, in which the metal elements are selected from metals and
metalloids, wherein the structure is fabricated by using a
precursor under a catalyst through a vapor phase synthesis
method.
16. The nanostructure according to claim 15, wherein the precursor
includes two substances selected from a first material to a third
material separately or in a combination thereof, and the binary
alloy for the nanostructure includes the first material containing
metal oxides, metal substances or metal halides of a metal used to
form the binary alloy, a second material containing metal oxides,
metal substances or metal halides of another metal used to form the
binary alloy, or the third material containing any one of binary
alloy substances for the binary alloy.
17. The nanostructure according to claim 15, wherein the vapor
phase synthesis method is heat treatment characterized in that the
precursor is maintained at 500 to 1200.degree. C. while a substrate
for fabrication of a binary alloy single-crystalline metal nanowire
is maintained at 700 to 1100.degree. C., and an inert gas flow is
introduced from the precursor to the substrate at 10 to 600 sccm
under pressure ranging from 2 to 30 torr.
18. The nanostructure according to claim 15, wherein the vapor
phase synthesis method is heat treatment characterized in that the
precursor is maintained at 500 to 1200.degree. C. while a substrate
for fabrication of a binary alloy single-crystalline metal nanobelt
is maintained at 100 to 200.degree. C., and an inert gas flow is
introduced from the precursor to the substrate at 10 to 600 sccm
under pressure ranging from 2 to 30 torr.
19. The nanostructure according to claim 16, wherein the binary
alloy nanowire is selected from a Pd.sub.xAu.sub.1-x
(0.01.ltoreq.x.ltoreq.0.99) single-crystalline metal nanowire, a
Co.sub.yAg.sub.1-y (0.01.ltoreq.x.ltoreq.0.5) single-crystalline
metal nanowire, a Ag.sub.2Te nanowire and a Bi.sub.1Te.sub.1
single-crystalline metal nanobelt.
20. The nanostructure according to claim 19, wherein the
Pd.sub.xAu.sub.1-x (0.01.ltoreq.x.ltoreq.0.99) single-crystalline
metal nanowire has a FCC (Face Centered Cubic) structure.
21. The nanostructure according to claim 20, wherein the
Pd.sub.xAu.sub.1-x (0.01.ltoreq.x.ltoreq.0.99) single-crystalline
metal nanowire is in the form of a solid solution.
22. The nanostructure according to claim 19, wherein the
Co.sub.yAg.sub.1-y (0.01.ltoreq.x.ltoreq.0.5) single-crystalline
metal nanowire has a FCC (Face Centered Cubic) structure.
23. The nanostructure according to claim 22, wherein the
Co.sub.yAg.sub.1-y (0.01.ltoreq.x.ltoreq.0.5) single-crystalline
metal nanowire is in the form of a solid solution.
24. The nanostructure according to claim 19, wherein the Ag.sub.2Te
single-crystalline metal nanowire has an SM (Simple Monoclinic)
structure.
25. The nanostructure according to claim 24, wherein the Ag.sub.2Te
single-crystalline metal nanowire is in the form of a compound.
26. The nanostructure according to claim 19, wherein the
Bi.sub.1Te.sub.1 single-crystalline metal nanobelt has a hexagonal
structure.
Description
[0001] This application claims priority to Korean Patent
Application No. 2007-0068548, filed on Jul. 9, 2007, in the Korean
Intellectual Property Office, the entire contents of which are
hereby incorporated by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to binary alloy
single-crystalline metal nanostructures and a fabrication method
thereof, and more particularly, to a binary alloy
single-crystalline nanostructure and a method for fabrication
thereof by vapor phase synthesis.
[0004] 2. Description of the Related Art
[0005] In recent years, one dimensional (1D) nanostructures often
represented by nanowires have been drawing extensive attention as a
material highly applicable, especially, in semiconductor
applications. Such nanostructures are expected to have various
advantages including decreased size, increased aspect ratio,
increased surface to volume ratio and, newly discovered phenomena
and unique characteristics owing to novel morphologies thereof,
which cannot be observed in bulk states.
[0006] In particular, there is a great deal of interest for binary
alloy nanowires useable in manufacturing gas sensors, magnetic
devices and/or magnetic sensors. There is an important requirement
for developing a variety of precision measurement sensors useful
for high precision works following recent advances in science and
technologies. Also, development of improved sensors with excellent
sensitivity by domestic and/or oversea research activities is still
a long way off.
[0007] Moreover, with regard to hydrogen gas sensors for highly
sensitive fuel cells that can detect hydrogen leaks that may occur,
if such fuel cells are to become commercially available on the
market, there is still a requirement that such sensors require much
more research and development together with novel fuel cells to be
used as a future clean energy.
[0008] In addition to the development of hydrogen sensors described
above, it is also important to investigate novel materials useable
in manufacturing the sensors. Among them, a PdAu nanowire is
receiving much attention, which comprises PdAu having strong
adhesiveness to hydrogen and can be applied to high precision
sensors. Since the PdAu nanowire shows no phase transition from
.alpha. to .beta. at a defined hydrogen concentration ranging from
0.1 to 2%, it is expected that this can improve a response time of
a hydrogen sensor if used in the sensor.
[0009] A CoAg alloy nanowire has magnetic properties such as
magnetic resistance MR, spin glass properties, etc., while an AgTe
alloy nanowire typically shows combined ionic and charge conductive
properties. When it. In a circumstance with high temperature, AgTe
substances include one having superionic conductivity and a high
content of Ag in a bulk condition and another having large positive
MR properties and a high content of Te. Therefore, both of the CoAg
alloy nanowire and the AgTe alloy nanowire are also expected to be
practically utilized in manufacturing nano-sized magnetic sensors
or magnetic devices.
[0010] However, it is known that CoAg alloy has positive combined
energy in a binary system of Co and Ag and it is difficult to
generate an intermetallic compound thereof. Thus, papers for
reviewing CoAg alloy were not disclosed before the 1990s. The
reported substances comprise kinds of thin films and nano particles
in amorphous and/or multi-crystalline forms.
[0011] Like CoAg alloy nanowires, no reports have yet disclosed the
fabrication of nanocables or single-crystalline metal nanowires
based on PdAu and/or AgTe alloys. There is still no disclosure that
introduces application of vapor phase synthesis in production of
binary alloy nanowires under catalyst free circumstances.
[0012] At present, it is difficult to produce nanocables using
binary metals and, even more, using single metals. Most of recently
disclosed documents have a focus on synthesis of nano-sized
structures using bulk metals. For synthesis of 1D nanostructures,
most of research groups make use of an anodic aluminum oxide
template as the most simple method. This method is most convenient
in synthesizing 1D nanostructures and is receiving increased
interest in an aspect of diameter control that can regulate the
diameter of a nanocable dependent on conditions for synthesis,
however, it has difficulty in synthesis of single-crystalline metal
nanowires.
[0013] Synthesis of single-crystalline metal nanowires is a
significant element in view of improved electric and magnetic
properties of raw substances. The most important factor related to
electric properties of a nanowire is a degree of electron
conductivity. For a single-crystalline metal nanowire, the nanowire
itself is a large grain boundary and has no obstacles against
electron conductivity in the nanowire.
[0014] On the other hand, a multi-crystalline metal nanowire which
comprises a number of grains and grain boundaries exhibits a
decrease in the electron conductivity due to electron scattering
caused by a number of boundary barriers.
[0015] For magnetic properties of a nanowire, an arrangement of
electron spin is substantially important when applying an external
field to the nanowire. As described above, the single-crystalline
metal nanowire has only a single crystal form to orient the
arrangement of electron spin in a single direction if the external
field is applied. While, the multi-crystalline metal nanowire as a
set of numerous crystals induces the crystals to arrange electron
spins in different directions during application of the external
field, thus resulting in reduction of magnetic properties
thereof.
[0016] In order to solve the above problems, the present inventors
intended to apply vapor phase synthesis of binary alloy
nanostructures using metal oxides, metal substances, metal halides
and/or binary alloy materials as a precursor and, as a result,
completed a process for production of a binary alloy
single-crystalline nanostructure with a completed morphology.
SUMMARY OF THE INVENTION
[0017] Accordingly, the present invention is directed to solve
problems of prior art as described above and, an object of the
present invention is to provide a binary alloy single-crystalline
nanostructure with high quality and improved morphology, and a
method for fabrication of the same through a vapor phase transport
method.
[0018] In order to accomplish the above object, the present
invention provides a method of fabricating a binary alloy
single-crystalline nanostructure, comprising: using two substances
selected from a first material to a third material separately or in
a combination thereof as a precursor; and heat treating the
precursor as well as a semiconductor or insulator
single-crystalline substrate under inert atmosphere after placing
the precursor on front part of a reaction furnace and the
single-crystalline substrate on rear part of the reaction furnace
to fabricate a binary alloy single-crystalline metal nanowire or
nanobelt, wherein the binary alloy for the nanostructure includes
the first material containing metal oxides, metal substances or
metal halides of a metal used to form the binary alloy, a second
material containing metal oxides, metal substances or metal halides
of another metal used to form the binary alloy, and/or the third
material containing any one of binary alloy substances for the
binary alloy.
[0019] According to the present invention, the precursor includes a
mixture of the first material and the second material, a mixture of
the first material and the third material, or the third material
alone.
[0020] Preferably, metal halides of the first material or the
second material are selected from a group consisting of metal
fluoride, metal chloride, metal bromide and metal iodide.
[0021] In case that the single-crystalline nanostructure according
to the present invention is a single-crystalline metal nanowire, an
inert gas flow is introduced through the front part to the rear
part of the furnace at 10 to 600 sccm, the heat treatment is
conducted under pressure ranging from 2 to 30 torr, and the
precursor is maintained at 500 to 1200.degree. C. while the
single-crystalline substrate is maintained at 700 to 1100.degree.
C.
[0022] In case that the single-crystalline nanostructure according
to the present invention is a single-crystalline metal nanobelt, an
inert gas flow is introduced through the front part to the rear
part of the furnace at 10 to 600 sccm, the heat treatment is
conducted under pressure ranging from 2 to 30 torr, and the
precursor is maintained at 500 to 1200.degree. C. while the
single-crystalline substrate is maintained at 100 to 200.degree.
C.
[0023] In a case that metal halides are used as the precursor, that
is, the precursor is a mixture containing metal halides of the
first material as well as the second material, it is preferable
that metal halides of the first material and the second material
are physically separate from each other and positioned at the front
part of the reaction furnace.
[0024] At this time, metal halides of the first material are
maintained at 500 to 800.degree. C. and the second material is
maintained at 800 to 1200.degree. C., while the single-crystalline
substrate is maintained at 700 to 1100.degree. C.
[0025] Preferably, metal oxides of the first material or the second
material are selected from a group consisting of silver oxide, gold
oxide, cobalt oxide, palladium oxide and tellurium oxide.
Preferably, metal substances of the first material or the second
material are selected from a group consisting of silver, gold,
cobalt, palladium and tellurium in terms of metal element.
Preferably, metal halides of the first material or the second
material are selected from a group consisting of silver halide,
gold halide, cobalt halide, palladium halide and tellurium halide.
Preferably, binary alloy substances of the third material include
Co and Ag alloy, Ag and Te alloy, or Bi and Te alloy.
[0026] Preferably, the binary alloy single-crystalline metal
nanowire formed on the single-crystalline substrate is selected
from a Pd.sub.xAu.sub.1-x (0.01.ltoreq.x.ltoreq.0.99)
single-crystalline metal nanowire, a Co.sub.yAg.sub.1-y
(0.01.ltoreq.y.ltoreq.0.5) single-crystalline metal nanowire, a
Ag.sub.2Te nanowire and a Bi.sub.1Te.sub.1 single-crystalline metal
nanobelt.
[0027] According to the present invention, there is provided a
binary alloy nanostructure comprising a solid solution of single
crystals of two metal elements or a compound of the single
crystals, in which the metal elements are selected from metals or
metalloids, wherein the structure is fabricated by using a
precursor under a catalyst through a vapor phase synthesis
method.
[0028] At this time, the precursor includes two substances selected
from a first material to a third material separately or in a
combination thereof, and the binary alloy for the nanostructure
includes the first material containing metal oxides, metal
substances or metal halides of a metal used to form the binary
alloy, a second material containing metal oxides, metal substances
or metal halides of another metal used to form the binary alloy,
and/or the third material containing any one of binary alloy
substances for the binary alloy.
[0029] In case that the single-crystalline nanostructure according
to the present invention is a single-crystalline metal nanowire,
the precursor is maintained at 500 to 1200.degree. C. while a
substrate for fabrication of a binary alloy single-crystalline
metal nanowire is maintained at 700 to 1100.degree. C., and an
inert gas flow is introduced from the precursor to the substrate at
10 to 600 sccm under pressure ranging from 2 to 30 torr to prepare
the nanowire.
[0030] In case that the single-crystalline nanostructure according
to the present invention is a single-crystalline metal nanobelt,
the precursor is maintained at 500 to 1200.degree. C. while a
substrate for fabrication of a binary alloy single-crystalline
metal nanobelt is maintained at 100 to 200.degree. C., and an inert
gas flow is introduced from the precursor to the substrate at 10 to
600 sccm under pressure ranging from 2 to 30 torr to prepare the
nanobelt.
[0031] Preferably, the binary alloy nanowire is selected from a
Pd.sub.xAu.sub.1-x (0.01.ltoreq.x.ltoreq.0.99) single-crystalline
metal nanowire, a Co.sub.yAg.sub.1-y (0.01.ltoreq.x.ltoreq.0.5)
single-crystalline metal nanowire, a Ag.sub.2Te nanowire and a
Bi.sub.1Te.sub.1 single-crystalline metal nanobelt.
[0032] Preferably, the Pd.sub.xAu.sub.1-x
(0.01.ltoreq.x.ltoreq.0.99) single-crystalline metal nanowire has a
FCC (Face Centered Cubic) structure. Preferably, the
Pd.sub.xAu.sub.1-x (0.01.ltoreq.x.ltoreq.0.99) single-crystalline
metal nanowire is in the form of a solid solution. Preferably, the
Co.sub.yAg.sub.1-y (0.01.ltoreq.x.ltoreq.0.5) single-crystalline
metal nanowire has a FCC (Face Centered Cubic) structure.
Preferably, the Co.sub.yAg.sub.1-y (0.01.ltoreq.x.ltoreq.0.5)
single-crystalline metal nanowire is in the form of a solid
solution.
[0033] Preferably, the Ag.sub.2Te single-crystalline metal nanowire
has an SM (Simple Monoclinic) structure. Preferably, the Ag.sub.2Te
single-crystalline metal nanowire is in the form of a compound.
Preferably, the Bi.sub.1Te.sub.1 single-crystalline metal nanobelt
has a hexagonal structure.
[0034] The present inventive method adopts a vapor phase transport
method without a catalyst to fabricate a binary alloy metal
nanowire, thus improving simplicity and reproducibility in working
processes for fabrication of the nanowire. This method also has
advantages in that the fabricated nanowire is a high quality
nanowire or nanobelt in a complete single-crystalline condition
without defects and the binary alloy nanowire or nanobelt can be
massively produced in a uniform size without coagulation on a
single-crystalline substrate.
BRIEF DESCRIPTION OF THE DRAWINGS
[0035] These and other objects, features, aspects, and advantages
of the present invention will be more fully described in the
following detailed description of preferred embodiments and
examples, taken in conjunction with the accompanying drawings. In
the drawings:
[0036] FIG. 1 is a diagram illustrating heat treatment of a
precursor and a substrate described in Example 2 of the present
invention;
[0037] FIG. 2 is a SEM (Scanning Electron Microscope) photograph of
a nanowire fabricated as described in Example 1 of the present
invention;
[0038] FIG. 3 is an XRD (X-Ray Diffraction) photograph of a
nanowire fabricated as described in Example 1 of the present
invention;
[0039] FIG. 4 shows a result monitored by EDS (Energy Dispersive
Spectroscopy) fixed to a TEM (Transmission Electron Microscope)
device for analysis of a nanowire fabricated as described in
Example 1 of the present invention;
[0040] FIG. 5 shows TEM analysis results for a nanowire fabricated
as described in Example 1 of the present invention, in particular,
FIG. 5(a) illustrates a dark field image; FIG. 5(b) is a high
magnitude TEM photograph of the nanowire shown in FIG. 5(a); and
FIG. 5(c) illustrates a SAED (Selected Area Electron Diffraction)
pattern of the nanowire shown in FIG. 5(a);
[0041] FIG. 6 is a SEM photograph of a nanowire fabricated as
described in Example 2 of the present invention;
[0042] FIG. 7 is an XRD photograph of a nanowire fabricated as
described in Example 2 of the present invention;
[0043] FIG. 8 illustrates a dark field image of a nanowire
fabricated as described in Example 2 of the present invention, in
particular, a SAED pattern of the nanowire being inserted in a
lower left part thereof;
[0044] FIG. 9 shows results monitored by EDS fixed to a TEM device
for analysis of constitutional ingredients of a nanowire fabricated
as described in Example 2 of the present invention, in particular,
FIG. 9(a) is an Ag EDS mapping result of the nanowire; FIG. 9(b) is
a Co EDS mapping result of the nanowire; FIG. 9(c) is an EDS result
of a white blank square portion indicated on an upper part of the
nanowire; and FIG. 9(d) is an EDS result of another white blank
square portion indicated on a lower part of the nanowire;
[0045] FIG. 10 is a SEM photograph of a nanowire fabricated as
described in Example 3 of the present invention;
[0046] FIG. 11 is an XRD result of a nanowire fabricated as
described in Example 3 of the present invention;
[0047] FIG. 12 shows TEM analysis results of a nanowire fabricated
as described in Example 3 of the present invention, in particular,
FIG. 12(a) illustrates a dark field image and SAED pattern of the
nanowire; FIG. 12(b) is a HRTEM (High Resolution Transmission
Microscopy) photograph of the nanowire shown in FIG. 12(a) and, in
addition, FFT (Fast Fourier Transform) pattern inserted in an upper
right part thereof;
[0048] FIG. 13 shows a result monitored by EDS fixed to a TEM
device for analysis of a nanowire fabricated as described in
Example 3 of the present invention;
[0049] FIG. 14 shows TEM analysis results of a Bi.sub.1Te.sub.1
nanobelt, in particular, FIG. 14(a) illustrates a dark field image
and SAED pattern of the nanobelt and FIG. 14(b) is a HRTEM
photograph of the nanobelt together with FFT pattern inserted in an
upper right part thereof;
[0050] FIG. 15 shows a result monitored by EDS fixed to a TEM
device for analysis of constitutional ingredients of a nanobelt
fabricated as described in Example 4 of the present invention;
and
[0051] FIG. 16 shows an XRD result of a nanobelt fabricated as
described in Example 4 of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0052] Hereinafter, preferred embodiments of the present invention
will be described in more detail by the following examples with
reference to the accompanying drawings.
[0053] The a method of fabricating a binary alloy
single-crystalline nanostructure of the present invention comprises
using two substances selected from a first, a second and a third
material separately or in a combination thereof as a precursor; and
heat treating the precursor as well as a semiconductor or insulator
single-crystalline substrate under inert atmosphere after placing
the precursor on front part of a reaction furnace and the
single-crystalline substrate on rear part of the reaction furnace
to fabricate a binary alloy single-crystalline metal nanowire or
nanobelt. In the present invention, the binary alloy for the
nanostructure includes the first material containing metal oxides,
metal substances or metal halides of a metal used to form the
binary alloy, the second material containing metal oxides, metal
substances or metal halides of another metal used to form the
binary alloy, and/or the third material containing any one of
binary alloy substances for the binary alloy.
[0054] The method of fabricating a binary alloy nanowire or a
nanobelt according to the present invention is characterized by
simply using a precursor, which is any one selected from binary
alloy materials and metal oxides, metal substances or -metal
halides of two metals used to form a binary alloy so as to
fabricate the nanowire or nanobelt on a substrate. The present
inventive method has improved simplicity and reproducibility in
fabrication processing because a binary alloy single-crystalline
metal nanowire or nanobelt can be fabricated without a catalyst
through a vapor phase transport path and, in addition, an advantage
of fabricating high purity nanostructures without impurities other
than the two metals used to form the binary alloy.
[0055] By regulating temperatures of front and rear parts of a
reaction furnace, respectively, and inert gas flow rate and
internal pressure of a heat treatment pipe during heat treatment,
this method ultimately controls nucleation driving power, growth
driving power, nucleation velocity and growth velocity so as to
control and reproduce size of the binary alloy single-crystalline
nanostructure and density of a substrate and further produce high
quality and good crystallinity binary alloy single-crystalline
nanostructures without defects.
[0056] A heat treatment condition, carrier gas (that is, inert gas)
flow rate and a pressure condition in heat treatment can be
independently adjustable. But, in order to obtain a binary alloy
single-crystalline metal nanowire with preferable quality and
morphology, it is desirable that all of these conditions are
altered dependent on other conditions. Therefore, specific defined
limits for these conditions have substantially no meanings
independently, however, a combination thereof can induce the most
preferable product, that is, the binary alloy single-crystalline
metal nanowire.
[0057] Temperatures of the front and the rear parts of the reaction
furnace, respectively, must be optimally defined depending on
physical properties of the precursor such as melting point,
vaporization point, vaporization energy, etc. and conditions for
carrier gas flow rate and pressure in heat treatment. Preferably,
the precursor is maintained at 500 to 1200.degree. C. while a
substrate is maintained at 700 to 1100.degree. C. for a nanowire
and at 100 to 200.degree. C. for a nanobelt.
[0058] The carrier gas, that is, an inert gas preferably flows from
the front part of the reaction furnace toward the rear part of the
same in an amount of 10 to 600 sccm. If the precursor includes
metal halides, the inert gas preferably flows from the front part
to the rear part of the furnace in an amount of 300 to 600 sccm
and, more preferably, 450 to 550 sccm. When the precursor does not
include metal halides, the inert gas preferably flows from the
front part to the rear part of the reaction furnace in an amount of
10 to 300 sccm. The pressure in heat treatment is preferably lower
than ordinary pressure, more preferably, ranges from 2 to 30 torr
and, most preferably, from 5 to 15 torr. However, in case of the
precursor comprising metal halides, there is no problem to apply
the ordinary temperature to fabrication of the nanowire.
[0059] Conditions such as temperature of a reaction furnace, inert
gas flow rate and pressure in heat treatment may influence various
parameters including: degree of gasification of a precursor; amount
of the precursor gasified and transferred per hour to a
single-crystalline substrate; nucleation and growth velocities of a
binary alloy material on the single-crystalline substrate; and
surface energy, degree of coagulation, and/or morphology of a
binary alloy material (such as nanowire or nanobelt) produced on a
single-crystalline substrate.
[0060] Accordingly, under such conditions in relation to the
temperature, the inert gas flow rate and the pressure in heat
treatment, a binary alloy nanowire or nanobelt with the most
preferable quality and morphology is produced by a vapor phase
transport method, using the precursor according to the present
invention. Beyond the defined ranges for the conditions described
above, it is difficult to fabricate a binary alloy based nanowire
and, even when a nanowire or nanobelt is produced, there may occur
some problems such as coagulation of the product, modified
morphologies, poor quality caused by defects or failure, or that
other metal materials in forms of a particle, rod, etc. are
generated instead of a preferable nanowire or nanobelt
morphology.
[0061] Heat treatment time should also be optimally defined under
the conditions described above including temperature, inert gas
flow rate and the pressure in heat treatment, and preferably,
ranges from 10 minutes to 1 hour. During the heat treatment time
defined above, the precursor gasified by the inert gas migrates to
a single-crystalline substrate to participate in nucleation and
nuclei growth and, simultaneously, a material transfer (in atomic
or cluster unit) occurs between binary alloy substances generated
on the substrate through a vapor phase and a surface of the
substrate, thus resulting in Oswald ripening.
[0062] Accordingly, the single-crystalline substrate on which the
binary alloy nanowire or nanobelt was formed after the heat
treatment, is again subjected to the heat treatment so as to
regulate density or size of the nanowire or nanobelt or the
like.
[0063] As described above, the fabrication method of the present
invention uses metal oxides, metal substances or metal halides of
two metal elements for fabricating a binary alloy metal nanowire or
nanobelt, otherwise, binary alloy materials of the above two metal
elements, as a precursor and adopts the vapor phase transport
method to produce the binary alloy nanowire or nanobelt. The binary
alloy single-crystalline metal nanowire or nanobelt formed on the
single-crystalline substrate preferably comprises
Pd.sub.xAu.sub.1-x (x is 0.01.ltoreq.x.ltoreq.0.99)
single-crystalline metal nanowire, Co.sub.yAg.sub.1-y (y is
0.01.ltoreq.y.ltoreq.0.5) single-crystalline metal nanowire,
Ag.sub.2Te single-crystalline metal nanowire or Bi.sub.1Te.sub.1
single-crystalline metal nanobelt and so on.
[0064] The precursor for fabricating the binary alloy
single-crystalline metal nanowire or nanobelt may include a mixture
or two separate materials containing two metal elements used to
fabricate a binary alloy.
[0065] In case of using a mixture as the precursor, the mixture may
be a mixture of the first material and the second material or
another mixture of the first material and the third material.
Alternatively, the precursor may comprise an alloy of the two metal
elements (which is substantially the third material) for
fabricating a binary alloy metal nanowire or nanobelt alone. The
mixture of the first and second materials includes, for example: a
mixture containing metal oxides of the first material and metal
oxides of the second material; a mixture containing metal
substances of the first material and metal oxides of the second
material; a mixture containing metal halides of the first material
and metal oxides of the second material; a mixture containing metal
oxide of the first material and metal substances of the second
material; a mixture containing metal substances of the first
material and metal substances of the second material; a mixture
containing metal halides of the first material and metal substances
of the second material; a mixture containing metal oxides of the
first material and metal halides of the second material; a mixture
containing metal substances of the first material and metal halides
of the second material; or a mixture containing metal halides of
the first material and metal halides of the second material. The
mixture preferably comprises a mixture containing metal oxides of
the first material and metal oxides of the second material, a
mixture containing metal substances of the first material and metal
oxides of the second material; a mixture containing metal oxides of
the first material and metal substances of the second material; or
a mixture containing metal substances of the first material and
metal substances of the second material.
[0066] The mixture of the first and third materials includes, for
example: a mixture containing metal oxides of the first material
and binary alloy substances of the third material; a mixture
containing metal substances of the first material and binary alloy
substances of the third material; or a mixture containing metal
halides of the first material and binary alloy substances of the
third material. Metal oxides of the first material and binary alloy
substances of the third material or metal substances of the first
material and binary alloy substances of the third material are
preferably used.
[0067] As the precursor, binary alloy substances of the third
material may be used alone.
[0068] The mixture is not a simple mixture of the first material
and the second material but means that two materials are positioned
adjacent to each other in the reaction furnace (at a position
maintaining the same temperature).
[0069] In particular, when using metal halides as the precursor,
metal halides of the first material are used together with the
second material and both of the materials are physically separate
from each other and preferably positioned at front part of the
reaction furnace. In order that the metal halides of the first
material are physically separate from the second material and both
materials are positioned on the front part of the reaction furnace,
the second material and the metal halides of the first material are
placed in difference pots and maintained at different temperatures,
respectively, to participate in synthesis of a nanowire or
nanobelt. Metal halides have relatively high volatility compared to
metals, binary metals and metal oxides, and thus there is a need to
control an amount of metal halide gas flowing to a substrate
according to the inert gas flow rate.
[0070] Herein, the precursor includes a mixture containing metal
halides of the first material and metal oxides of the second
material, a mixture containing metal halides of the first material
and metal substances of the second material, or a mixture
containing metal halides of the first material and metal halides of
the second material. Preferably, the precursor includes a mixture
containing metal halides of the first material and metal oxides of
the second material or a mixture containing metal halides of the
first material and metal substances of the second material.
[0071] Alternatively, the precursor may include a mixture
containing metal halides of the first material and binary alloy
substances of the third material. Metal halides of the first
material as well as the second material (or the third material) are
physically separate from each other and placed on the front part of
the reaction furnace. Temperature of metal halides of the first
material ranges from 500 to 800.degree. C., while temperature of
the second material (or the third material) ranges from 800 to
1200.degree. C. The substrate is preferably maintained at 700 to
1100.degree. C. for a nanowire and 100 to 200.degree. C. for a
nanobelt, respectively.
[0072] If the reaction furnace has a single thermostat, the
precursor is placed in a uniform zone of a reactor pipe and other
materials or the substrate is located at another position defined
by adjusting a distance between the precursor and the uniform zone
in order to control temperature. In case that a heating element as
well as the thermostat are installed independent of the reaction
furnace, temperature of the reaction furnace can be controlled by
operation of the thermostat.
[0073] Metal halides of the first material or the second material
are selected from a group consisting of metal fluoride, metal
chloride, metal bromide and metal iodide and, preferably, include
silver halide, gold halide, cobalt halide, palladium halide or
tellurium halide. Silver halide is preferably selected from a group
consisting of silver fluoride, silver chloride, silver bromide and
silver iodide. Likewise, gold halide is selected from a group
consisting of gold halide, gold chloride, gold bromide and gold
iodide; cobalt halide is selected from cobalt fluoride, cobalt
chloride, cobalt bromide and cobalt iodide; palladium halide is
selected from a group consisting of palladium fluoride, palladium
chloride, palladium bromide and palladium iodide; and tellurium
halide is selected from a group consisting of tellurium fluoride,
tellurium chloride, tellurium bromide and tellurium iodide.
[0074] Metal oxides of the first material or the second material
are preferably selected from a group consisting of silver oxide,
gold oxide, cobalt oxide, palladium oxide and tellurium oxide.
Herein, gold oxide, cobalt oxide, palladium oxide or tellurium
oxide may be an oxide having a desired stoichiometric ratio with
thermodynamic stability at ordinary temperature under ordinary
pressure. However, such oxide may not have a stable stoichiometric
ratio due to point defects caused by metal ingredients or
oxygen.
[0075] Metal substances of the first material or the second
material are preferably silver, gold, cobalt, palladium or
tellurium.
[0076] Binary alloy substances of the third material are preferably
selected from a group consisting of: Pd and Au (PdAu) alloy; Co and
Ag (CoAg) alloy; Ag and Te (AgTe) alloy; and Bi and Te (BiTe)
alloy. PdAu alloy, CoAg alloy or AgTe alloy may take the form of an
inter-metallic compound, compound or solid solution. Constitutional
composition of the alloy is preferably similar to that of a
nanowire or nanobelt to be fabricated, although the composition may
be different from that of the nanowire or nanobelt.
[0077] Meanwhile, a semiconductor or a non-conductor
single-crystalline substrate is made of any one of semiconductors
or non-conductors, which are chemically or thermally stable under
certain heat treatment conditions described above. The substrate
preferably includes any one selected form a single-crystalline
substrate based on a group IV element such as silicon, germanium or
silicon germanium; a single-crystalline substrate based on group
III-V elements such as gallium-arsenic, indium-phosphorous or
gallium-phosphorous; a single-crystalline substrate based on group
II-VI elements; a single-crystalline substrate based on group IV-VI
elements; a sapphire single-crystalline substrate; or a silicon
dioxide single-crystalline substrate.
[0078] However, the substrate only plays a role of providing a
space on which a nanowire or nanobelt is formed and, if necessary,
may be a poly-crystalline substance of a substance included the
single-crystalline substrate made of any one selected from the
materials described above.
[0079] In order to experimentally identify improvements of the
present inventive fabrication method, a Pd.sub.xAu.sub.1-x
(0.01.ltoreq.x.ltoreq.0.99) single-crystalline metal nanowire, a
Co.sub.yAg.sub.1-y (0.01.ltoreq.y.ltoreq.0.5) single-crystalline
metal nanowire, a Ag.sub.2Te nanowire and a Bi.sub.1Te.sub.1
single-crystalline metal nanobelt were prepared according to the
method of the present invention (see Examples 1 to 4).
[0080] The following Example 1 is a representative example
illustrating a method of fabricating a binary alloy nanowire
without using a halide based precursor. Example 2 describes a
method for fabrication of a binary alloy nanowire using a halide
based precursor, Example 3 describes a method for fabrication of a
binary alloy nanowire using a binary alloy substances used to form
the binary alloy nanowire, and Example 4 illustrates a method for
fabrication of a binary alloy nanobelt using binary alloy
substances used to form the binary alloy nanobelt,
respectively.
[0081] As described above, although Example 3 illustrates only the
specific binary alloy substance of Ag.sub.2Te as the precursor, a
combination of the binary alloy substance of Ag.sub.2Te and Ag in a
form of a metal element or a combination of the binary alloy
substance of Ag.sub.2Te and a specific metal oxide such as
Ag.sub.2O.sub.3 can also be applied instead of Ag.sub.2Te.
Likewise, although only the binary alloy substance of
Bi.sub.1Te.sub.1 is used in Example 4 as the precursor, it can be
replaced by a combination of the binary alloy substance of
Bi.sub.1Te.sub.1 and Bi in the form of a metal element or a
combination of the binary alloy substance of Bi.sub.1Te.sub.1 and a
metal oxide of Bi.sub.2O.sub.3.
EXAMPLE 1
[0082] A Pd.sub.xAu.sub.1-x (0.01.ltoreq.x.ltoreq.0.99)
single-crystalline metal nanowire was synthesized in a reaction
furnace using a vapor phase transport method.
[0083] The reaction furnace is generally divided into front and
rear parts and equipped with a heating element and a thermostat,
independently. The reaction furnace has a built-in quartz tube with
a diameter of 2.54 cm (1 in) and a length of 60 cm (23.6 in).
[0084] A boat type container made of high purity alumina material
was located in the middle of the front part of the furnace, to
which a mixture including 0.03 g of Au.sub.2O.sub.3 (Sigma-Aldrich,
334057) and 0.03 g of PdO (Sigma-Aldrich, 203971) was added as a
precursor. A sapphire single-crystalline substrate (surface (0001))
was positioned in the middle of the rear part of the reaction
furnace. Argon gas flow was introduced to the front part and
exhausted out of the rear part of the reaction furnace. To the rear
part of the furnace, a vacuum pump was fixed to maintain an
internal pressure of the quartz tube at 5 torr. Ar gas flow rate
was controlled to 150 sccm using MFC (mass flow controller).
[0085] While maintaining temperatures of the alumina boat
containing the precursor in the front part and the silicon
substrate in the rear part of the furnace at 1100.degree. C. and
950.degree. C., respectively, the heat treatment was conducted for
30 minutes to produce the Pd.sub.xAu.sub.1-x
(0.0.ltoreq.x.ltoreq.0.99) single-crystalline metal nanowire as a
final product.
EXAMPLE 2
[0086] A Co.sub.yAg.sub.1-y (0.01.ltoreq.y.ltoreq.0.5)
single-crystalline metal nanowire was synthesized in a reaction
furnace using a vapor phase transport method.
[0087] The reaction furnace is generally divided into front and
rear parts and equipped with a heating element and a thermostat,
independently. The reaction furnace has a built-in quartz tube with
a diameter of 2.54 cm (1 in) and a length of 60 cm (23.6 in).
[0088] Two boat type containers made of high purity alumina
material were located in the middle of the front part of the
furnace, in which 0.01 g of CoCl.sub.2 (Sigma-Aldrich, 449776) and
0.3 g of Ag.sub.2O (Sigma-Aldrich, 22163) were placed as
precursors, respectively. A Si single-crystalline substrate
(surface (100)) was positioned in the middle of the rear part of
the reaction furnace. A melting pot made of alumina containing
Au.sub.2O.sub.3 was placed in the middle of the front part of the
reaction furnace.
[0089] Argon gas flow was introduced to the front part and
exhausted out of the rear part of the reaction furnace. To the rear
part of the furnace, a vacuum pump was fixed to maintain an
internal pressure of the quartz tube at 15 torr. Ar gas flow rate
was controlled to 500 sccm using MFC.
[0090] Temperature of the front part (located in the middle of the
furnace) was controlled to 1000.degree. C. to allow the melting pot
containing Ag.sub.2O being maintained at 1000.degree. C., another
melting pot containing CoCl.sub.2 was placed at a distance of 4 cm
(1.57 in) apart from the melting pot containing Ag.sub.2O so that
the CoCl.sub.2 containing pot was maintained at 650.degree. C.
[0091] Whiling maintaining temperature of the rear part of the
furnace to 800.degree. C., the heat treatment was conducted for 30
minutes to produce the Co.sub.yAg.sub.1-y
(0.01.ltoreq.y.ltoreq.0.5) single-crystalline metal nanowire as a
final product. To more clearly understand, construction of the heat
treatment process as well as the precursors described in Example 2
were shown in FIG. 1.
EXAMPLE 3
[0092] An Ag.sub.2Te single-crystalline metal nanowire was
synthesized in a reaction furnace using a vapor phase transport
method.
[0093] The reaction furnace is generally divided into front and
rear parts and equipped with a heating element and a thermostat,
independently. The reaction furnace has a built-in quartz tube with
a diameter of 2.54 cm (1 in) and a length of 60 cm (23.6 in).
[0094] A boat type container made of high purity alumina material
was located in the middle of the front part of the reaction
furnace, in which 0.05 g of Ag.sub.2Te (Sigma-Aldrich, 400645) was
placed as a precursor. A Si single-crystalline substrate (surface
(100)) was positioned in the middle of the rear part of the
reaction furnace.
[0095] Ar gas flow was introduced to the front part and exhausted
out of the rear part of the reaction furnace. To the rear part of
the furnace, a vacuum pump was fixed to maintain an internal
pressure of the quartz tube at 10 torr. Ar gas flow rate was
controlled to 200 sccm using MFC.
[0096] While maintaining temperatures of the alumina boat
containing the precursor in the front part and the silicon
substrate in the rear part of the furnace at 1000.degree. C. and
800.degree. C., respectively, the heat treatment was conducted for
30 minutes to produce the Ag.sub.2Te single-crystalline metal
nanowire as a final product.
EXAMPLE 4
[0097] A Bi.sub.1Te.sub.1 single-crystalline metal nanobelt was
synthesized in a reaction furnace using a vapor phase transport
method.
[0098] The reaction furnace is generally divided into front and
rear parts and equipped with a heating element and a thermostat,
independently. The reaction furnace has a built-in quartz tube with
a diameter of 2.54 cm (1 in) and a length of 60 cm (23.6 in).
[0099] A boat type container made of high purity alumina material
was located in the middle of the front part of the furnace, in
which 0.05 g of Bi.sub.2Te.sub.3 (Alfa Aeasr, 44077) was placed as
a precursor. A Si single-crystalline substrate (surface (100)) was
positioned in the middle of the rear part of the reaction
furnace.
[0100] Ar gas flow was introduced to the front part and exhausted
out of the rear part of the reaction furnace. To the rear part of
the furnace, a vacuum pump was fixed to maintain an internal
pressure of the quartz tube at 10 torr. Ar gas flow rate was
controlled to 200 sccm using MFC.
[0101] While maintaining temperatures of the alumina boat
containing the precursor in the front part and the silicon
substrate in the rear part of the furnace at 600.degree. C. and
150.degree. C., respectively, the heat treatment was conducted for
30 minutes to produce the Bi.sub.1Te.sub.1 single-crystalline metal
nanobelt as a final product.
[0102] All of the resulting products, that is, the binary alloy
single-crystalline metal nanowires in Examples 1 to 3 and the
binary alloy single-crystalline metal nanobelt in Example 4 were
subjected to an analysis to monitor quality, morphology, purity,
etc. of the products.
[0103] FIG. 2 to FIG. 5 show results measured for the
Pd.sub.xAu.sub.1-x (0.0.ltoreq.x.ltoreq.0.99) single-crystalline
metal nanowire fabricated by Example 1.
[0104] More particularly, FIG. 2 is a SEM photograph illustrating a
Pd.sub.xAu.sub.1-x (0.01.ltoreq.x.ltoreq.0.99) single-crystalline
metal nanowire formed on a sapphire single-crystalline substrate.
As shown in FIG. 2, a number of nanowires with uniform dimensions,
each of which has diameter ranging 50 to 150 nm and length of more
than 30 um (preferably, 30 to 50 um), were fabricated independent
of the sapphire single-crystalline substrate. The nanowires had a
linearly extended form in the direction of a longitudinal axis, a
plurality of nanowires were individually separable without being
held together, and the longitudinal axis of the nanowires was
substantially perpendicular to surface of the substrate.
[0105] FIG. 3 shows an XRD result for the Pd.sub.xAu.sub.1-x
(0.01.ltoreq.x.ltoreq.0.99) single-crystalline metal nanowire
verifying that the nanowire had crystallinity, which was different
from that obtained for each of the Pd metal element and Au metal
element.
[0106] FIG. 4 shows a result monitored by EDS fixed to a TEM device
for analysis of constitutional ingredients of the nanowire in
Example 1. From the result, it was understood that the fabricated
nanowire comprised only Pd and Ag except additional materials
inevitably measured due to characteristics of a certain measuring
instrument such as a grid. Further, EDS analysis results for a
number of nanowires fabricated according to the present inventive
method demonstrated that Pd.sub.xAu.sub.1-x nanowires were
fabricated (wherein, 0.01.ltoreq.x.ltoreq.0.99).
[0107] FIG. 5 shows TEM analysis results for the Pd.sub.xAu.sub.1-x
(0.01.ltoreq.x.ltoreq.0.99) single-crystalline metal nanowire, in
particular, FIG. 5(a) illustrates a dark field image of the
nanowire; FIG. 5(b) is a high magnitude TEM photograph of the
nanowire shown in FIG. 5(a); and FIG. 5(c) illustrates a SAED
pattern of the nanowire shown in FIG. 5(a).
[0108] Referring to FIGS. 5(a) and 5(b), it was found that a number
of nanowires with smooth surface and a uniform thickness were
produced. FIG. 5(c) showed that the fabricated nanowire was a
single-crystalline product having FCC (face centered cubic)
structure and a specified orientation of [100] for grain
growth.
[0109] From the results monitored in FIG. 2 to FIG. 5, it was
clearly understood that the fabricated nanowire was a
single-crystalline product with FCC structure, which contained a
solid solution of Pd and Au, and exhibited high quality and
excellent morphology.
[0110] FIG. 6 to FIG. 8 show results measured for the
Co.sub.yAg.sub.1-y (0.01.ltoreq.y.ltoreq.0.5) single-crystalline
metal nanowire fabricated by Example 2.
[0111] More particularly, FIG. 6 is a SEM photograph illustrating a
Co.sub.yAg.sub.1-y (0.01.ltoreq.y.ltoreq.0.5) single-crystalline
metal nanowire formed on a Si single-crystalline substrate. FIG. 6
showed that a plate as well as the nanowire were formed
simultaneously. From the high magnitude SEM photograph inserted in
the upper left part of FIG. 6, it was demonstrated that a number of
nanowires with uniform dimensions, each of which has diameter
ranging 200 to 300 nm and length of more than several um, were
fabricated independent of the Si substrate. The nanowires had a
linearly extended form in the direction of a longitudinal axis, and
a plurality of nanowires were individually separable without being
held together.
[0112] The XRD result in FIG. 7 demonstrated that the fabricated
nanowire had an FCC structure, which was substantially the same as
that of bulk Ag.
[0113] FIG. 8 illustrates a dark field image of a
Co.sub.yAg.sub.1-y (0.01.ltoreq.y.ltoreq.0.5) single-crystalline
metal nanowire and, in particular, a SAED pattern of the nanowire
being inserted in the lower left part of FIG. 8.
[0114] From the results monitored in FIG. 8, it was clearly
understood that the fabricated nanowire was a single-crystalline
product with FCC structure and a specified orientation of [011] for
grain growth.
[0115] FIG. 9 shows results monitored by EDS fixed to a TEM device
for analysis of constitutional ingredients of a nanowire, in
particular, FIG. 9(a) is an Ag EDS mapping result of the nanowire;
FIG. 9(b) is a Co EDS mapping result of the nanowire; FIG. 9(c) is
an EDS result of a white blank square portion indicated on an upper
part of the nanowire; and FIG. 9(d) is an EDS result of an
alternative white blank square portion indicated on a lower part of
the nanowire.
[0116] From the results shown in FIG. 9(a) to 9(d), it was found
that the fabricated nanowire comprised only Co and Ag except
additional materials inevitably measured due to characteristics of
a certain measuring instrument such as a grid and, in addition, Co
and Ag ingredients were homogeneously dispersed in the nanowire.
Further, EDS analysis results for a number of nanowires fabricated
according to the present inventive method demonstrated that
Co.sub.yAg.sub.1-y nanowires were fabricated (wherein,
0.01.ltoreq.y.ltoreq.0.5).
[0117] From the results monitored in FIG. 6 to FIG. 9, it was
clearly understood that the fabricated nanowire was a
single-crystalline product with FCC structure, which contained a
solid solution of Co and Ag, and exhibited high quality and
excellent morphology.
[0118] FIG. 10 to FIG. 13 show results measured for the Ag.sub.2Te
single-crystalline metal nanowire fabricated by Example 3.
[0119] More particularly, FIG. 10 is a SEM photograph illustrating
a Ag.sub.2Te single-crystalline metal nanowire formed on a sapphire
single-crystalline substrate.
[0120] As shown in FIG. 10, it was demonstrated that a number of
nanowires with uniform dimensions, each of which has diameter
ranging 150 to 200 nm and length of more than several um, were
fabricated independent of the sapphire single-crystalline
substrate. The nanowires had a linearly extended form in the
direction of a longitudinal axis, and a plurality of nanowires were
individually separable without being held together.
[0121] The XRD result in FIG. 11 demonstrated that the fabricated
Ag.sub.2Te nanowire had an SM (Simple Monoclinic) structure, which
was substantially the same as that of bulk Ag.sub.2Te.
[0122] FIG. 12 shows TEM analysis results of a Ag.sub.2Te nanowire,
in particular, FIG. 12(a) illustrates a dark field image and SAED
pattern of the nanowire; FIG. 12(b) is a HRTEM photograph of the
nanowire shown in FIG. 12(a) and, in addition, FFT pattern inserted
in an upper right part of FIG. 12(b).
[0123] Referring FIG. 12(a), it was found that a number of
nanowires with smooth surface and a uniform thickness were obtained
and each of the fabricated nanowires was a single-crystalline
product having an SM structure and a specified orientation of [302]
for grain growth.
[0124] As shown in the HRTEM photograph of FIG. 12(b), it can be
clearly understood that the fabricated nanowire was a high quality
single-crystalline product without defects and an interplanar
(crystal) distance of the nanowire was 4.46 .ANG., which was
substantially the same as that of bulk Ag.sub.2Te (010).
[0125] From the result monitored by EDS fixed to a TEM device for
analysis of constitutional ingredients of a nanowire as shown in
FIG. 13, it was understood that the fabricated nanowire comprised
only Ag and Te except additional materials inevitably measured due
to characteristics of a certain measuring instrument such as a grid
and, in addition, a relative ratio of Ag to Te was 2:1.
[0126] From the results monitored in FIG. 10 to FIG. 13, it can be
clearly understood that the fabricated Ag.sub.2Te nanowire was a
single-crystalline product with an SM structure and a relative
ratio of 2:1 for Ag to Te, and exhibited high quality and excellent
morphology.
[0127] FIG. 14 shows TEM analysis results of a Bi.sub.1Te.sub.1
nanobelt, in particular, FIG. 14(a) illustrates a dark field image
and SAED pattern of the nanobelt.
[0128] Referring FIG. 14(a), it was found that a nanobelt with
smooth surface and a uniform thickness was obtained. Also, FIG.
14(b) is a HRTEM photograph of the nanobelt together with FFT
pattern inserted in an upper right part thereof.
[0129] FIGS. 14(a) and (b) showed that the fabricated nanobelt was
a single-crystalline product having a hexagonal structure and a
specified orientation of [110] for grain growth.
[0130] FIG. 15 shows a result monitored by EDS fixed to a TEM
device for analysis of constitutional ingredients of a nanobelt
fabricated as described in Example 4 of the present invention.
[0131] FIG. 16 shows an XRD result of a nanobelt fabricated as
described in Example 4 of the present invention.
[0132] While the present invention has been described with
reference to the preferred embodiment, it will be understood by
those skilled in the art that various modifications and variations
may be made therein without departing from the scope of the present
invention as defined by the appended claims.
* * * * *