U.S. patent application number 10/815842 was filed with the patent office on 2005-07-14 for method for assembling carbon nanotubes and microprobe and an apparatus thereof.
This patent application is currently assigned to Industrial Technology Research Institute. Invention is credited to Chang, Hui-Ling, Huang, Hsin-Chien, Lee, Yuh-Wen, Lin, Wei-Chin, Su, Hui-Chi.
Application Number | 20050150767 10/815842 |
Document ID | / |
Family ID | 34738213 |
Filed Date | 2005-07-14 |
United States Patent
Application |
20050150767 |
Kind Code |
A1 |
Su, Hui-Chi ; et
al. |
July 14, 2005 |
Method for assembling carbon nanotubes and microprobe and an
apparatus thereof
Abstract
The present invention discloses a method for assembling carbon
nanotubes and microprobe, which employs the Electrophoresis or
Dielectrophoresis principles to drive the carbon nanotubes
self-assembling the microprobe under an electric field. The method
comprises the steps of: forming at least one microprobe, the
microprobe being covered by a conductive layer; exposing the
microprobe to a solution having carbon nanotubes spreading therein,
the solution being furnished with an electrode; applying a
predetermined voltage between the conductive layer and the
electrode, making at least one carbon nanotube to move and attach
onto the top of the microprobe.
Inventors: |
Su, Hui-Chi; (KaoHsiung,
TW) ; Huang, Hsin-Chien; (Hsinchu, TW) ; Lee,
Yuh-Wen; (Hsinchu, TW) ; Lin, Wei-Chin;
(SanChung City, TW) ; Chang, Hui-Ling; (Hsinchu,
TW) |
Correspondence
Address: |
BRUCE H. TROXELL
SUITE 1404
5205 LEESBURG PIKE
FALLS CHURCH
VA
22041
US
|
Assignee: |
Industrial Technology Research
Institute
|
Family ID: |
34738213 |
Appl. No.: |
10/815842 |
Filed: |
April 2, 2004 |
Current U.S.
Class: |
204/483 ;
977/848 |
Current CPC
Class: |
B82Y 30/00 20130101;
C25D 13/00 20130101 |
Class at
Publication: |
204/483 ;
977/DIG.001 |
International
Class: |
C25D 013/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 14, 2004 |
TW |
93101013 |
Claims
What is claimed is:
1. A method for assembling carbon nanotubes and microprobes,
comprising following steps: forming at least one microprobe on an
substrate, the microprobe being covered by a conductive layer;
exposing an tip of the microprobe to a solution having carbon
nanotubes spreading therein, the solution being furnished with an
electrode; and applying a predetermined voltage between the
conductive layer and the electrode, making at least one carbon
nanotube to move and attach onto the tip of the microprobe
2. The method for assembling carbon nanotubes and microprobe of
claim 1, wherein the surface area of the electrode exposed to the
solution is larger than that of the tip of the microprobe.
3. The method for assembling carbon nanotubes and microprobe of
claim 1 further comprising a step of: providing ultrasonic
oscillation to the solution for preventing the carbon nanotubes
from gathering together.
4. The method for assembling carbon nanotubes and microprobe of
claim 1, further comprising a step of: covering a non-conductive
material on the conductive layer and exposing only the potion of
the conductive layer covering the tip of the microprobe.
5. The method for assembling carbon nanotubes and microprobe of
claim 1, wherein the substrate is made of silicon.
6. The method for assembling carbon nanotubes and microprobe of
claim 5, wherein the microprobe is formed on the substrate using
semiconductor processing.
7. The method for assembling carbon nanotubes and microprobe of
claim 6, wherein the step of forming a microprobe on a substrate
comprises following steps: forming a silicon nitride layer and a
mask layer successively on the substrate, the mask layer having a
plurality of openings disposed at predetermined positions thereof
to expose the portion of the silicon nitride layer defined by the
plural openings; etching away the portion of the silicon nitride
layer defined by the plural openings, and removing the mask layer;
applying anisotropic etching on the silicon nitride to form at
least one silicon nitride microprobe on the substrate; forming a
conductive layer on the substrate covering at least the tip of the
microprobe; and forming a non-conductive layer covering a
predetermined area of the conductive except for the portion of the
conductive layer covering the tip of the microprobe.
8. The method for assembling carbon nanotubes and microprobe of
claim 7, wherein the non-conductive layer is a photoresist.
9. The method for assembling carbon nanotubes and microprobe of
claim 1, wherein the solution includes an anionic surfactant
capable of attaching a layer of negative charges onto the surface
of the carbon nanotubes, and the conductive layer is connected to
the positive of a predefined power supply.
10. The method for assembling carbon nanotubes and microprobe as
claimed in claim 1, wherein the solution is isopropyl alcohol.
11. A structure assembling carbon nanotubes and microprobes,
comprising: a substrate having at least a microprobe formed
thereon; a conductive layer covering at least a tip of the
microprobe; and at least one carbon nanotube attaching on the tip
of the microprobe and parallel to the extending direction of the
microprobe.
12. The structure assembling carbon nanotubes and microprobes of
claim 11, wherein the substrate is made of silicon.
13. The structure assembling carbon nanotubes and microprobes of
claim 11, wherein the microprobe is made of silicon nitrite.
14. The structure assembling carbon nanotubes and microprobes of
claim 11, wherein a non-conductive material covers a predetermined
area of the conductive layer except for the portion of the
conductive layer covering the tip of the microprobe.
15. The structure assembling carbon nanotubes and microprobes of
claim 14, wherein the non-conductive material is a photoresist.
16. The structure assembling carbon nanotubes and microprobes of
claim 11, wherein the carbon nanotube is attached on the tip of the
microprobe by Van der Waal's force.
17. An apparatus for assembling carbon nanotubes and microprobes,
comprising: a solution, containing a plurality of carbon nanotubes
dispersed and suspended therein; an electrode, disposed in the
solution; at least one microprobe, disposed in the solution and at
least the tip of the microprobe being covered by a conductive
layer; and a direct current power source, connecting the conductive
layer and the electrode, capable of applying a predetermined
voltage to drive the carbon nanotubes suspended in the solution to
move toward the conductive layer covering the tip of the microprobe
and attach onto the same.
18. The apparatus for assembling carbon nanotubes and microprobes
of claim 17, wherein the microprobe is formed on a substrate, and
the conductive layer covers the surface of the substrate and the
microprobe, and a non-conductive layer further covers the
conductive layer except for the portion of the conductive layer
covering the tip of the microprobe.
19. The apparatus for assembling carbon nanotubes and microprobes
of claim 17 further comprising an ultrasonic device for providing
ultrasonic oscillation to the solution so as to prevent the carbon
nanotubes from gathering together.
20. The apparatus for assembling carbon nanotubes and microprobes
of claim 17, wherein the solution includes an anionic surfactant
capable of attaching a layer of negative charges onto the surface
of the carbon nanotubes, and the conductive layer is connected to
the positive of a predefined power supply.
21. The apparatus for assembling carbon nanotubes and microprobes
of claim 17, wherein the solution is isopropyl alcohol.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to a method and an apparatus
for assembling carbon nanotubes and microprobes, and more
particularly, to a method and an apparatus for assembling carbon
nanotubes and microprobes capable of employing the principles of
Electrophoresis/Dielectrophoresis to drive the carbon nanotubes
self-assembling the microprobe under an electric field.
BACKGROUND OF THE INVENTION
[0002] Carbon nanotubes are single-layered/multilayered tubular
carbon molecules that have properties that make them potentially
useful in nanotechnology. They exhibit unusual strength and unique
electrical properties, and are extremely efficient conductors of
heat A nanotube is a structure similar to a fullerene, only the
carbon atoms are rolled into a cylinder instead of a sphere; each
end is capped with half a fullerene molecule. They are only several
nanometers wide, and their length can be millions of times greater
than their width, that is, several micrometers long. Carbon
nanotubes have many structures, differing in length, thickness,
type of spiral, and number of layers. Although they are formed from
essentially the same graphite sheet, their electrical
characteristics differ depending on these variations, acting either
as metals or semiconductors. Carbon nanotubes are expected to
become a key material in ultrafine devices of the future, because
of their unique electrical characteristics, and their
extraordinarily fine structure on a nanometer scale. Other merits
offered by carbon nanotubes are light weight, extremely high
mechanical strength (they have larger tensile strength than steel),
their ability to withstand extreme heat of 2000.degree. C. in the
absence of oxygen, and the fact that they emit electrons
efficiently when subjected to electrical field. Currently, research
is being conducted throughout the world targeting the application
of carbon nanotubes as materials for use in photoelectric elements,
electronic elements, biochemistry medication, fuel cell, etc.
Moreover, the high tensile strength, semi-conductivity and
flexibility features thereof can be applied to a microprobe or a
microelectrode of nanometer level. However, due to the tiny
diameter of the carbon nanotubes, it is difficult to assembly a
carbon nanotube to a microprobe.
[0003] While assembling a carbon nanotube with a microprobe, the
conventional method is by adopting a chemical vapor deposition
(CVD) process along with a catalyst deposition technique for
growing the carbon nanotube at the place adhered with the catalyst,
such as: plasma enhanced chemical vapor deposition, normal
atmospheric temperature chemical vapor deposition, arc discharge,
etc. However, these processes must be performed in a vacuum
environment (50.about.400 Torr) or under a very high temperature.
Even a low temperature CVD will require at least
450.about.500.degree. C. and can only be used for multi-walled
carbon nanotube (MWNTs). On the other hand, a high temperature of
1000.about.1200.degree. C. is needed for single-walled carbon
nanotubes (SWNTs). Such conventional techniques will have
difficulties when depositing carbon nanotubes on a large-scale
substrate under low temperature. Furthermore, the catalyst is
usually made of materials such as iron, nickel, or molybdenum,
etc., in nanometer-sized powder which are not only expensive, but
also will generate by-products like crystal or non-crystal carbides
and residual catalyst during the process of carbon nanotube
deposition. Therefore, an additional purification processes will be
needed and the difficulty of the whole process also increase. The
present invention provides a method for driving the carbon
nanotubes self-assembling the microprobe under an electric field
for overcoming the obstacle of assembling a nano-sized matter with
a much larger structure.
SUMMARY OF THE INVENTION
[0004] The primary object of the invention is to provide a method
for assembling a carbon nanotube and a microprobe under normal
atmospheric temperature and pressure.
[0005] Another object of the invention is to provide a method for
assembling a carbon nanotube and a microprobe capable of employing
the principles of Electrophoresis/Dielectrophoresis to drive the
carbon nanotubes attaching itself on the tip of a microprobe under
a high electric field.
[0006] Yet another object of the invention is to provide a
composite by assembling carbon nanotubes and a microprobe and the
carbon nanotubes being attached to the tip of the microprobe in
parallel to the direction of an electric field.
[0007] Another object of the invention is to provide an apparatus
for assembling a carbon nanotube and a microprobe capable of
performing the process of driving the carbon nanotubes to attach
itself on the tip of a microprobe under a high electric field.
[0008] In order to achieve the aforementioned objectives, the
method for assembling carbon nanotubes and microprobe of the
invention comprises the following steps: forming at least one
microprobe, the microprobe being covered by a conductive layer;
exposing the microprobe to a solution having carbon nanotubes
spreading therein, the solution being furnished with an electrode;
applying a predetermined voltage between the conductive layer and
the electrode for making at least one carbon nanotube to move and
attach onto the top of the microprobe.
[0009] Following drawings are cooperated to describe the detailed
structure and its connective relationship according to the
invention for facilitating your esteemed members of reviewing
committee in understanding the characteristics and the objectives
of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] FIG. 1 is a schematic diagram showing a system for
assembling carbon nanotubes and microprobes by electrophoresis (or
dielectrophoresis) effect; and
[0011] FIG. 2A to 2E are flow charts showing the process of making
a substrate with microprobes.
DESCRIPTION OF THE PREFERRED EMBODIMENT
[0012] The invention utilizing the electrophoresis (or
dielectrophoresis) effect to assembling carbon nanotubes and a
microprobe under normal atmospheric temperature and pressure.
[0013] Please refer to FIG. 1, which is a schematic diagram showing
an apparatus for assembling carbon nanotubes and microprobes by
electrophoresis (or dielectrophoresis) effect.
[0014] As shown in FIG. 1, a silicon substrate 11 with at least one
microprobe 12 (four probes 12 are provided in FIG. 1 as example)
formed thereon by semiconductor processing is provided. A
conductive layer 13 is formed and covers the surface of the
substrate 11 and the microprobe 12. The conductive layer 13 can be
made of materials such as gold, copper, aluminum and other metals
or alloys, and it is preferred to form such conductive layer by
electroplating or film deposition. In addition, a non-conductive
layer 14 is formed and covering the conductive layer 13. Although a
photoresist is selected as the non-conductive layer 14 for the
present preferred embodiment, other non-conductive material can be
used as the non-conductive layer 14 also. The non-conductive layer
14 covers a predetermined area of the conductive layer 13 such that
the portion of the conductive layer covering the tip 121 of the
microprobe 12 is not covered by the non-conductive material 14 and
is exposed.
[0015] The substrate 11 along with the microprobe 12, the
conductive layer 13 and the non-conductive layer 14 are placed in a
container having a solution 20 therein, such as a reaction tank,
and a plurality of carbon nanotubes 21 is suspended in the solution
20. An electrode 31 is disposed in a position separated from the
substrate 11 by a predetermined distance in the solution 20. The
conductive layer 13 and the electrode 31 are connected respectively
to the positive and negative of a DC power supply 45 providing a
preset DC voltage via conductive grease 41, 42. Since only the
portion of the conductive layer 12 covering the tip 121 of the
microprobe 12 is exposed to the solution 20, the electrode 31 has a
much larger area exposed to the solution 20 than that of the
microprobe 12. Therefore, an electric field concentration will
occur at the tip 121 of the microprobe 12. Under the circumstance,
most of the carbon nanotubes 21 in the solution 20 will move toward
the tip 121 of the microprobe 12 by electrophoresis (or
dielectrophoresis) effect, in addition, at the tip of the
microprobe, the carbon nanotubes driven by the electric field are
oriented longitudinally parallel to the electric field which is
aligned with the extending direction of the microprobe 12, and
further are attached to the tip 121 of the microprobe 12 by Van der
Waal's force.
[0016] In a preferred embodiment, the solution 20 includes an
anionic surfactant, such as Sodium dodecyl sulfate (SDS) or other
surfactant, for attaching a layer of negative charges onto the
surface of the carbon nanotubes 21. The conductive layer 13 is
connected to the positive of the DC power supply 45 and the
electrode 31 is connected to the negative of the DC power supply 45
(as shown in FIG. 1). Thus, the negative-charged carbon nanotubes
21 will move toward the tip 121 of the microprobe 12
(positive-charged) and attached to the tip 121 of the microprobe 12
by Van der Waal force. This is called electrophoresis (EP). The
mobility of the carbon nanotubes 21 depends on the molecular weight
thereof and is irrelevant to the charge born in the molecule.
[0017] In another preferred embodiment, the solution 20 is
un-charged, such as isopropyl alcohol or other organic solution.
Since the carbon nanotube 21 itself is un-charged, it will not
actively move toward any electrode. However, as the conductive
layer 13 exposed to the solution 20 is only at the tip 121 of the
microprobe 12, the area thereof exposed to the solution 20 is far
small than that of the electrode 31. Therefore, the electric field
will concentrate and intensify in the vicinity of the tip 121 of
the microprobe 12 that enables the happening of a non-uniform
electric intensity distribution. Under the influence of the
inhomogeneous electric field, the un-charged carbon nanotubes 21
are polarized and thus induced to move sideway, that is, a dipole
moment is being generated on the surface of a particle due to the
polarization effect induced by an electric field. In this regard,
even both the isopropyl alcohol and the carbon nanotubes 21 are
uncharged, the carbon nanotubes 21 will be affected by the
inhomogeneous electric field and be driven to move toward the
position with higher electric field density, and eventually are
attached to that position The above phenomenon is referred as
dielectrophoresis.
[0018] In this preferred embodiment, the apparatus of the present
invention can further comprise an ultrasonic device 46 for
providing ultrasonic oscillation to the solution 20 so as to
prevent the carbon nanotubes 21 from gathering together and enable
the carbon nanotubes 21 to be uniformly dispersed and suspended in
the solution 21.
[0019] FIG. 2A to FIG. 2E shows a processing step of the substrate
11 with microprobes 12 of FIG. 1 according to a preferred
embodiment of the present invention.
[0020] First, as seen in FIG. 2A, a silicon nitride layer 52 and a
mask layer 53 (e.g. a photoresist) are formed successively on the
silicon substrate 51 (e.g. a silicon wafer). A photolithography and
development--is applied to form several openings 531 in a
predetermined position of the mask layer 53 to expose the portion
of the silicon nitride layer 52 defined by the openings 531.
[0021] Following, as shown in FIG. 2B, the device of FIG. 2A is
processed by reactive ion etching (RIE) and uses the substrate 51
as the end of the etching process, such that the exposed portion of
the silicon nitride layer 52 defined by the openings 531 is
development, and then the mask layer 53 is removed from the
substrate to leave only several silicon nitride columns 521
disposed on the substrate.
[0022] Next, as shown in FIG. 2C, several tapered silicon nitride
probe 522 are formed on the substrate 51 by applying anisotropic
etching on the silicon nitride columns 521.
[0023] Next, as shown in FIG. 2D, a conductive layer 54 (such as
gold, copper, aluminum, nickel or other metals or alloys) is formed
on the substrate 51 and probe 522 by electroplating, sputtering,
physical vapor deposition, chemical vapor deposition or other
methods. In the preferred embodiment, the conductive layer 54
covers the entire substrate 51 and probe 522. However, in other
embodiments, the conductive layer 54 covers at least the tip of the
probe 522.
[0024] Finally, as shown in FIG. 2E, a non-conductive layer 55 is
formed on a predetermined area of the conductive layer 54 in a way
that only the potion of the conductive layer 541 covering the tip
of the probe 522 is exposed. In the preferred embodiment, the
non-conductive layer 55 can be a photoresist, other non-conductive
film or polymer material. The formation is, first, covering the
entire conductive layer 54 with the photoresist, and then a
predetermined thickness of the photoresist is etched using RIE to
expose only the tip of the probe 522. Thus, the substrate with
probe of FIG. 1 is accomplished.
[0025] Although, the material of the microprobe used in FIGS. 2A to
2E is silicon nitride (SiN4), other materials, such as silicon
oxide, metal or polymer can also be used for forming the probe on
the substrate.
[0026] While the preferred embodiment of the invention has been set
forth for the purpose of disclosure, modifications of the disclosed
embodiment of the invention as well as other embodiments thereof
may occur to those skilled in the art. Accordingly, the appended
claims are intended to cover all embodiments which do not depart
from the spirit and scope of the invention.
* * * * *