U.S. patent application number 10/564408 was filed with the patent office on 2007-02-08 for carbon nanotube manufacturing apparatus and method for manufacturing carbon nanotube.
Invention is credited to Norio Akamatsu, Hiroshi Nishikado, Kensuke Yano.
Application Number | 20070031317 10/564408 |
Document ID | / |
Family ID | 34074112 |
Filed Date | 2007-02-08 |
United States Patent
Application |
20070031317 |
Kind Code |
A1 |
Akamatsu; Norio ; et
al. |
February 8, 2007 |
Carbon nanotube manufacturing apparatus and method for
manufacturing carbon nanotube
Abstract
A carbon nanotube manufacturing method is employed, in which a
carbon nanotube manufacturing apparatus (1000, 2000, 3000)
comprises an ionizing means (e.g., a negative ion generator (10))
for ionizing a vapor of a certain carbon-containing compound, an
electric field generating means (e.g., a direct-current power
supply (21), a cathode (22) and an anode (23)) for generating an
electric field and a heating means (e.g., a high-frequency heater
(30)) for heating a growth substrate (50, 55) disposed within the
electric field generated by the electric field generating means,
and in which a vaporized gas of the carbon-containing compound, the
vaporized gas being ionized, is caused to pass through the electric
field and to come into contact with the heated growth substrate, so
that a well aligned growth of carbon nanotube (4) on the growth
substrate can be obtained.
Inventors: |
Akamatsu; Norio;
(Tokushima-shi, JP) ; Nishikado; Hiroshi; (Tokyo,
JP) ; Yano; Kensuke; (Tokyo, JP) |
Correspondence
Address: |
FINNEGAN, HENDERSON, FARABOW, GARRETT & DUNNER;LLP
901 NEW YORK AVENUE, NW
WASHINGTON
DC
20001-4413
US
|
Family ID: |
34074112 |
Appl. No.: |
10/564408 |
Filed: |
July 18, 2003 |
PCT Filed: |
July 18, 2003 |
PCT NO: |
PCT/JP03/09172 |
371 Date: |
August 1, 2006 |
Current U.S.
Class: |
423/447.1 ;
423/447.6 |
Current CPC
Class: |
B82Y 30/00 20130101;
B82Y 40/00 20130101; C01B 2202/08 20130101; C01B 32/162
20170801 |
Class at
Publication: |
423/447.1 ;
423/447.6 |
International
Class: |
D01F 9/12 20060101
D01F009/12 |
Claims
1. A carbon nanotube manufacturing apparatus having an aligned
growth means for causing an aligned of a plurality of carbon
nanotubes quasi-vertically on a growth substrate, wherein said
aligned growth means comprises: an ionizing means for ionizing the
vaporized gas of a predetermined carbon-containing compound; an
electric field generating means for generating an electric field;
and a heating means for heating said growth substrate placed within
the electric field generated by said electric field generating
means, and wherein said aligned growth means is adapted to cause
the vaporized gas of said carbon-containing compound, the vaporized
gas being ionized by said ionizing means, to pass through an
electric field generated by said electric field generating means,
thereby causing the vaporized gas of said carbon-containing
compound to come into contact with said growth substrate.
2. A carbon nanotube manufacturing apparatus according to claim 1,
wherein said growth substrate is a substrate having a catalyst film
formed on the surface of a silicon layer containing silicon or a
silicon compound.
3. A carbon nanotube manufacturing apparatus according to claim 1
or claim 2, wherein said ionizing means comprises a negative ion
generator, and wherein said negative ion generator provides
electrons to the vaporized gas of said carbon-containing compound
to negatively charge the vaporized gas of said carbon-containing
compound.
4. A carbon nanotube manufacturing apparatus according to any one
of claims 1 to 3, comprising: a growth substrate forming means for
forming said growth substrate by forming growth film on a surface
of a predetermined metal substrate and forming a catalyst film on a
surface of said growth film; a growth film removing means, for
removing said growth film after the aligned growth of carbon
nanotubes by said aligned growth means; and a substrate forming
means for dissolving said metal substrate, embedding one ends of
said carbon nanotubes disposed on the surface of said metal
substrate in said metal substrate, and then solidifying said metal
substrate.
5. A carbon nanotube manufacturing apparatus according to any one
of claims 1 to 3, comprising: a growth substrate forming means for
forming a catalyst film on a surface of a silicon substrate to form
said growth substrate; a metal substrate forming means for
inserting the tips of said carbon nanotubes into molten metal after
the aligned growth of carbon nanotubes by said aligned growth
means, and thereafter solidifying said metal, to thereby form a
metal substrates; and a separating means for separating said carbon
nanotubes from said silicon substrate.
6. A carbon nanotube manufacturing method, comprising: a growth
film formation step for forming a growth film on a surface of a
predetermined metal substrate; a catalyst film formation step for
forming a catalyst film formed from a predetermined catalyst on the
surface of said growth film formed in said growth film formation
step; an aligned growth step for causing an aligned growth of a
plurality of carbon nanotubes on the surface of said metal
substrate through said growth film, by causing a catalytic reaction
between said catalyst forming said catalyst film formed by said
catalyst film formation step and the vaporized gas of a
predetermined carbon-containing compound; a growth removal step for
removing said growth film to dispose, on the surface of said metal
substrate, said carbon nanotubes alignedly grown by said aligned
growth step; and a substrate formation step for dissolving said
metal substrate, embedding one end of each of said carbon nanotubes
disposed on the surface of said metal substrate, and thereafter
solidifying said metal substrate.
7. A carbon nanotube manufacturing method, comprising: a catalyst
film formation step for forming a catalyst film formed from a
predetermined catalyst on the surface of a predetermined substrate;
an aligned growth step for causing a catalytic reaction between
said catalyst forming said catalyst film formed by said catalyst
film formation step and the vaporized gas of a predetermined
carbon-containing compound, to thereby cause an aligned growth of a
plurality of carbon nanotubes quasi-vertically on the surface of
said growth substrate; a carbon nanotube implanting step for
dissolving a predetermined metal substrate, inserting the tips of
said carbon nanotubes alignedly grown by said aligned growth step
into said molten metal substrate, and thereafter solidifying said
metal substrate; and a substrate separation step for separating
said carbon nanotubes from said growth substrate.
8. A carbon nanotube manufacturing method, comprising: a catalyst
film formation step for forming a catalyst film formed from a
predetermined catalyst on a surface of a predetermined growth
substrate; an aligned growth step for causing a catalytic reaction
between said catalyst forming said catalyst film formed by said
catalyst film formation step and the vaporized gas of a
predetermined carbon-containing compound, to thereby cause an
aligned growth of a plurality of carbon nanotubes quasi-vertically
on the surface of said growth substrate; a metal film vapor
deposition step for vapor depositing a predetermined metal film
layer on the side having the tips of said carbon nanotubes
alignedly grown by said aligned growth step; metal layer formation
step for forming a predetermined metal layer on said metal film
formed by said metal film vapor deposition step; and a substrate
separation step for separating said carbon nanotubes from said
growth substrate.
9. A carbon nanotube manufacturing method according to claim 8,
wherein said substrate separation step comprises: a second step of
aligned growth for causing an aligned growth of said carbon
nanotubes separated from said growth substrate in said substrate
separation step: a second step of metal layer formation for forming
a predetermined metal layer on side surfaces of said carbon
nanotubes alignedly grow in said second step of aligned growth and
on a surface of said metal film in which rear ends of said carbon
nanotubes are embedded; a metal layer slicing step for slicing, in
the direction perpendicular to the aligned growth of said carbon
nanotubes, said metal layer formed and laminated by said second
step of metal layer formation, to thereby form a slice having a
predetermined thickness; and a metal layer removal step for
removing, in the direction of aligned growth of said carbon
nanotubes, a predetermined amount of metal layer of said slice
formed in said metal layer slicing step, to thereby expose a
predetermined amount of said carbon nanotubes.
10. A carbon nanotube manufacturing apparatus according to any one
of claims 6 to 9, wherein said aligned growth step comprises: an
ionizing step for ionizing the vaporized gas of a predetermined
carbon-containing compound; an electric field application step for
applying an electric field to the vaporized gas of said
carbon-containing compound, the vaporized gas being ionized in said
ionizing step; and a heating step for heating said metal substrate
or said growth substrate, and wherein, in said electric field
application step, an electric field is applied to the vaporized gas
of said carbon-containing compound, the vaporized gas being ionized
in said electric field application step, to bring the vaporized gas
of said carbon-containing compound into contact with said metal
substrate or said growth substrate, thereby causing an aligned
growth of a plurality of carbon nanotubes quasi-vertically on the
surface of said metal substrate or said growth substrate.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to a carbon nanotube
manufacturing apparatus and a carbon nanotube manufacturing
method.
BACKGROUND OF THE INVENTION
[0002] In recent years, carbon nanotubes are receiving much
attention as for electrode materials such as FED (field emission
display) electrodes, capacitor electrodes, and battery electrodes,
as well as functional materials for hydrogen storage.
[0003] In particular, when an electric field is applied to carbon
nanotubes disposed on a conductive substrate perpendicularly, the
field concentrates to the tips of carbon nanotubes because the
carbon nanotube has a very small diameter, attracts electrons to
the tips of carbon nanotubes, ultimately electrons are emitted from
the tips without difficulty. In addition, if the electric
resistance of the substrate is low, the electrons which are
depleted by the emission can be easily supplied to increase the
amount of electron emission, facilitating the electron emission to
be maintained.
[0004] Conventionally, as a method of aligned growth of the carbon
nanotubes vertically on a substrate, there is known a method
disclosed in the Japanese Patent Laid-open Publication
JP-A-2003-12312, in which a silicon substrate having iron catalyst
vapor deposited on the surface thereof is heated while the
substrate is being dipped in an alcohol solution such as methanol
or ethanol, causing highly aligned carbon nanotubes to be
precipitated and grown.
[0005] In accordance with the above patent disclosure, however, a
silicon substrate, while being dipped in an alcohol solution, must
be heated to approximately 900 degrees centigrade to synthesize and
grow carbon nanotubes, and the alcohol solution has to be kept at a
temperature below its boiling point. In addition, since a large
quantity of alcohol solution is used, it is indispensable to
sufficiently take care of the maintenance and control of the carbon
nanotube synthesizing apparatus, in order to prevent the explosion
and fire outbreak caused by the mixing of vaporized alcohol with
the air. Since the growth direction of the carbon nanotubes is
controlled by the temperature gradient at the surface of the
silicon substrate, the temperature thereof must be appropriately
controlled in order to allow a well aligned growth.
[0006] Therefore, one of the objects of the present invention is to
provide a carbon nanotube manufacturing apparatus and a a carbon
nanotube manufacturing method which require easier maintenance and
control and which allows the highly aligned growth of carbon
nanotubes.
SUMMARY OF THE INVENTION
[0007] The present invention has been made in view of the above
circumstances and has an object to overcome the above problems and
to provide a carbon nanotube manufacturing apparatus (1000, 2000)
including an aligned growth means (e.g., an aligned growth
apparatus 300) for allowing a well aligned growth of a plurality of
carbon nanotubes (4) on a growth substrate (50, 55) in a generally
vertical direction,
[0008] wherein said aligned growth means comprises:
[0009] an ionizing means (e.g., a negative ion generator 10) for
ionizing a vaporized gas of a predetermined carbon-containing
compound;
[0010] an electric field generating means (e.g., an electric field
generator 20) for generating an electric field; and
[0011] a heating means (e.g., a high-frequency heater 30) for
heating said growth substrate disposed within the electric field
generated by said electric field generating means, and
[0012] wherein said aligned growth means causes the vaporized gas
of said carbon-containing compound, the vaporized gas being
negatively charged by said ionizing means, to pass through the
electric field generated by said electric field generating means,
causing the vaporized gas of said carbon-containing compound to
come into contact with said growth substrate.
[0013] In accordance with the carbon nanotube manufacturing
apparatus of the present invention, the carbon nanotube
manufacturing apparatus causes the vaporized gas of a predetermined
carbon-containing compound, the vaporized gas being ionized by an
ionizing means, to pass through the electric field generated by an
electric field generating means, causing the vaporized gas of the
carbon-containing compound to come into contact with a growth
substrate. The growth substrate at this stage has been heated by a
heating means, so that the vaporized gas of the carbon-containing
compound brought into contact with the growth substrate can have a
higher reactivity due to the heat, is pyrolyzed into water,
hydrogen, and carbon, so that the carbons form the carbon
nanotubes. The carbon nanotubes formed in this manner grow in good
alignment with the direction of the electric field due to the
effect of the electric field, allowing the well aligned carbon
nanotubes to be manufactured.
[0014] Therefore, well aligned carbon nanotubes can be manufactured
with easier maintenance and control than the previous method of
formation of carbon nanotubes by dipping a silicon substrate within
an alcohol solution.
[0015] In the carbon nanotube manufacturing apparatus in accordance
with the present invention,
[0016] said growth substrate is preferably a substrate with a
catalyst film (3) formed on the surface of a silicon layer (e.g., a
silicon film 2, a silicon substrate 5) comprising the silicon or a
silicon compound. If the growth substrate is a substrate with a
catalyst film formed on the surface of the silicon layer having the
silicon or silicon compound, a well aligned growth of carbon
nanotubes thereon is suitably obtained.
[0017] The silicon and silicon compound are materials for suitably
growing carbon nanotubes, so that the carbon nanotubes can be
suitably grown thereon. Some materials for the silicon layer
includes silicon (Si) and silicon compound, for example, silicon
carbide.
[0018] The catalyst film is a material which is necessary for the
aligned growth of carbon nanotubes and which promotes the growth as
well. For the catalyst film, some materials such as iron, iron
oxide, cobalt, and nickel, may be used.
[0019] Also in the carbon nanotube manufacturing apparatus in
accordance with the present invention,
[0020] said ionizing means comprises a negative ion generator
(10),
[0021] said negative ion generator provides electrons to the
vaporized gas of said carbon-containing compound, to thereby
negatively charge the vaporized gas of said carbon-containing
compound. If the ionizing means is a negative ion generator,
because the negative ion generator provides electrons to the
vaporized gas of the carbon-containing compound, allowing the
vaporized gas of the carbon-containing compound to be negatively
charged, the vaporized gas of the carbon-containing compound can be
negatively charged in a much secured manner.
[0022] In the carbon nanotube manufacturing apparatus in accordance
with the present invention,
[0023] said apparatus may comprise:
[0024] a growth substrate forming means (e.g., a growth film
forming apparatus 100 and a catalyst film forming apparatus 200)
for forming said growth substrate by forming a growth film (e.g., a
silicon film 2) on a surface of a predetermined metal substrate
(1), followed by forming a catalyst film (3) on a surface of said
growth film;
[0025] a growth film removing means (e.g., a growth film removing
apparatus 400) for removing said growth film after the aligned
growth of carbon nanotubes by said aligned growth means; and
[0026] a substrate forming means (e.g., a substrate forming
apparatus 500) for melting said metal substrate, embedding in said
metal substrate one end (4a) of each of said carbon nanotubes
disposed on the surface of said metal substrate, and then
solidifying said metal substrate.
[0027] In the carbon nanotube manufacturing apparatus, the growth
substrate forming means forms a growth film on a surface of a
predetermined metal substrate and deposits a catalyst film on the
surface of the growth film to thereby form a growth substrate, then
the growth film removing means removes the growth film after the
aligned growth of carbon nanotubes by the aligned growth means, the
substrate forming means melts the metal substrate, embeds one end
of each of the carbon nanotubes disposed on the surface of the
metal substrate and thereafter solidifies the metal substrate, so
that the well aligned carbon nanotubes can be manufactured.
[0028] Since a plurality of carbon nanotubes manufactured in this
manner have one end embedded in the metal substrate and are
implanted quasi-vertically on the surface of the metal substrate,
almost all of the carbon nanotubes are well aligned in the
longitudinal direction and are arranged in a quasi-parallel
manner.
[0029] The metal substrate may be a substrate formed from a metal
including such as copper, aluminium, chromium, and stainless
steel.
[0030] The growth film is a thin film formed from a material for
suitably growing carbon nanotubes. Such materials for suitably
growing carbon nanotubes include among others silicon (Si) and
silicon compounds such as for example silicon carbide (SiC).
[0031] With the plurality of well aligned carbon nanotubes orderly
arranged as such, an electric field can be applied in the
longitudinal direction of almost all carbon nanotubes, and the
electric field is concentrated at the tips of carbon nanotubes, so
as to locally concentrate electrons thereto, allowing the electron
emission at a high efficiency. Consequently, the resistance becomes
lower to facilitate the electric current to flow easier, thereby
increasing the efficiency of electron emission.
[0032] Since one end of each of the carbon nanotubes is embedded in
the metal substrate, the carbon nanotubes are immobilized within
the metal substrate, thereby increasing the fixing force between
the carbon nanotubes and the metal substrate to reduce the
probability of dropout of the carbon nanotubes and to ultimately
increase the durability.
[0033] In the carbon nanotube manufacturing apparatus in accordance
with the present invention,
[0034] the apparatus may comprise:
[0035] a growth substrate forming means (e.g., a catalyst film
forming apparatus 200) for forming a catalyst film (3) on a surface
of a silicon substrate (5) to form said growth substrate;
[0036] a metal substrate forming means (e.g., a substrate forming
apparatus 550) for inserting one end (4b) of each of said carbon
nanotubes into a molten metal after the aligned growth of carbon
nanotubes by said aligned growth means, and thereafter solidifying
said metal, to thereby form a metal substrate (1A); and
[0037] a separating means (e.g., a substrate separating apparatus
600) for separating said carbon nanotubes from said silicon
substrate.
[0038] The carbon nanotube manufacturing apparatus forms a growth
substrate by forming a catalyst film on the surface of a silicon
substrate by the growth substrate forming means, then, after the
aligned growth of carbon nanotubes by the aligned growth means,
inserts the tips of carbon nanotubes into the molten metal by the
metal substrate forming means, forms thereafter a metal substrate
by solidifying the molten metal, and separates the carbon nanotubes
from the silicon substrate by the separating means, thereby
manufacturing well aligned carbon nanotubes.
[0039] Since a plurality of carbon nanotubes manufactured in this
manner have the tips thereof being embedded in the metal substrate
and are implanted quasi-vertically on the surface of the metal
substrate, almost all of the carbon nanotubes are well aligned in
the longitudinal direction and orderly arranged in a quasi-parallel
manner.
[0040] The silicon substrate is a substrate formed from a silicon
material for suitably growing carbon nanotubes thereon. Some
exemplar silicon materials for suitably growing carbon nanotubes
include among others silicon (Si) and silicon compounds such as for
example silicon carbide (SiC).
[0041] The metal which forms the metal substrate includes for
example copper, aluminium, chromium, and stainless steel.
[0042] As the tips of carbon nanotubes are embedded in the metal
substrate, the carbon nanotubes are immobilized within the metal
substrate and the fixing force between the carbon nanotubes and the
metal substrate increases, to reduce the probability of dropout of
the carbon nanotubes and to thereby increase the durability.
[0043] By transplanting the well aligned carbon nanotubes orderly
grown on a silicon substrate into a metal substrate, the silicon
substrate can be reused, allowing an expensive silicon substrate to
be used for a plurality of cycles, to thereby reducing the
manufacturing.
[0044] A carbon nanotube manufacturing method in accordance with
the first aspect of the present invention includes:
[0045] a growth substrate formation step (e.g., a growth film
forming apparatus 100, step S102) for forming a growth film on the
surface of a predetermined metal substrate;
[0046] a catalyst film formation step (e.g., a catalyst film
forming apparatus 200, step S103) for forming a catalyst film
formed from a predetermined catalyst on the surface of said film
formed in said growth film forming step;
[0047] an aligned growth step (e.g. an aligned growth apparatus
300, step S104) for causing a well aligned growth of a plurality of
carbon nanotubes quasi-vertically on the surface of said metal
substrate via said growth film by causing a catalytic reaction
between said catalyst forming said growth film formed in said
catalyst film formation step and the vaporized gas of a
predetermined carbon-containing compound;
[0048] a growth film removal step (e.g., growth film removing
apparatus 400, step S105) for removing said growth film to dispose
on the surface of said metal substrate said carbon nanotubes
alignedly grown in said aligned growth step; and
[0049] a substrate formation step (e.g., a substrate forming
apparatus 500, step S106) for melting said metal substrate,
embedding one end of each of said carbon nanotubes disposed on the
surface of said metal substrate into said metal substrate, and
thereafter solidifying said metal substrate.
[0050] In the carbon nanotube manufacturing method in accordance
with the first aspect of the present invention, a growth film is
formed on the surface of a predetermined metal substrate by the
growth film formation step in the carbon nanotube manufacturing
method, a catalyst film is formed on the surface of the growth film
by the catalyst film formation step, a plurality of carbon
nanotubes are well alignedly grown quasi-vertically on the surface
of the metal substrate through the growth film by causing a
catalytic reaction between the catalyst forming the catalyst film
and the vaporized gas of a predetermined carbon-containing compound
in the aligned growth step, the carbon nanotubes are disposed on
the surface of the metal substrate by removing the growth film in
the growth film removal step, one end of each of the carbon
nanotubes is embedded in the molten metal substrate and thereafter
the metal substrate is solidified in the substrate forming step, to
thereby manufacture the well aligned carbon nanotubes.
[0051] In other words, the catalytic reaction of the catalyst
forming the catalyst film with the vaporized gas of a predetermined
carbon-containing compound provides the orderly aligned growth of a
plurality of carbon nanotubes quasi-vertically on the surface of a
metal substrate, allowing the manufacture of carbon nanotubes.
Therefore, well aligned carbon nanotubes can be manufactured with
easier maintenance and control than the previous formation method
of carbon nanotubes by dipping a silicon substrate within an
alcohol solution.
[0052] Since a plurality of carbon nanotubes manufactured in this
manner have one ends being embedded in the metal substrate and are
implanted quasi-vertically on the surface of the metal substrate,
most of all of the carbon nanotubes are well aligned in the
longitudinal direction and arranged in a quasi-parallel manner.
[0053] The growth film is a thin film formed from a material for
suitably growing carbon nanotubes. Such materials for suitabely
growing carbon nanotubes include among others silicon (Si) and
silicon compounds such as for example silicon carbide (SiC).
[0054] The catalyst film is a material which is necessary for the
aligned growth of the carbon nanotubes and which promotes the
growth. The materials for the catalyst film include such as iron,
iron oxide, cobalt, and nickel.
[0055] With the plurality of well aligned carbon nanotubes orderly
arranged as such, an electric field can be applied in the
longitudinal direction of almost all carbon nanotubes, and the
electric field is concentrated at the tips of carbon nanotubes, so
as to locally concentrate electrons thereto, allowing electron
emission at a high efficiency. Consequently, the resistance becomes
lower to facilitate the electric current to flow easier, thereby
increasing the efficiency of electron emission.
[0056] Since one end of carbon nanotube is embedded in the metal
substrate, the carbon nanotubes are immobilized within the metal
substrate, thereby increasing the fixing force between the carbon
nanotubes and the metal substrate, to reduce the probability of
dropout of the carbon nanotubes and to ultimately increase the
durability.
[0057] The carbon nanotube manufacturing method in accordance with
the second aspect of the present invention comprises:
[0058] a catalyst film formation step (e.g., catalyst film forming
apparatus 200, step S202) for forming a catalyst film formed from a
predetermined catalyst on the surface of a predetermined growth
substrate;
[0059] an aligned growth step (e.g., an aligned growth apparatus
300, step S203) for orderly growing a plurality of well aligned
carbon nanotubes quasi-vertically on the surface of said metal
substrate via said growth film by causing a catalytic reaction
between said catalyst forming said growth film formed in said
catalyst film forming step and the vaporized gas of a predetermined
carbon-containing compound;
[0060] a carbon nanotube implanting step (e.g., a substrate forming
apparatus (carbon nanotube implanting apparatus) 550, step S204)
for melting a predetermined metal substrate, inserting the tips of
said well aligned carbon nanotubes orderly grown in said aligned
growth step into said molten metal substrate, and thereafter
solidifying said metal substrate; and
[0061] a substrate separation step (e.g., a substrate separating
apparatus 600, step S205) for separating said carbon nanotubes from
said growth substrate;
[0062] In accordance with the carbon nanotube manufacturing method
of the second aspect of the present invention, the catalyst film
formation step in the carbon nanotube manufacturing method forms a
catalyst film on the surface of a predetermined growth substrate,
the aligned growth step causes the catalytic reaction between the
catalyst forming the catalyst film and the vaporized gas of a
predetermined carbon-containing compound to cause a plurality of
well aligned carbon nanotubes to be orderly grown quasi-vertically
on the surface of the metal substrate through the growth film, the
substrate formation step inserts the tips of carbon nanotubes into
the molten metal substrate and solidifies thereafter the metal
substrate, and substrate separation step separates carbon nanotubes
from the growth substrate, to thereby manufacture well aligned
carbon nanotubes.
[0063] In other words, the catalytic reaction between the catalyst
forming the catalyst film and the vaporized gas of a predetermined
carbon-containing compound causes the aligned growth of a plurality
of carbon nanotubes quasi-vertically on the surface of the growth
substrate, allowing the manufacture of the carbon nanotubes.
Consequently, the well aligned carbon nanotubes can be manufactured
with easier maintenance and control than the previous formation
method of carbon nanotubes by dipping a silicon substrate in an
alcohol solution.
[0064] Since a plurality of carbon nanotubes manufactured in this
manner have one end being embedded in the metal substrate and are
implanted quasi-vertically on the surface of the metal substrate,
almost all of the carbon nanotubes are well aligned in the
longitudinal direction and are orderly arranged in a quasi-parallel
manner.
[0065] The growth substrate is a substrate formed from a material
for suitably growing carbon nanotubes. Such materials for suitably
growing carbon nanotubes include among others silicon (Si) and
silicon compounds such as for example silicon carbide (SiC).
[0066] The catalyst film is a material which is necessary for
causing the aligned growth of carbon nanotubes and which promotes
the growth. The materials for the catalyst film include such as
iron, iron oxide, cobalt, and nickel.
[0067] With the plurality of well aligned carbon nanotubes orderly
arranged as such, an electric field can be applied in the
longitudinal direction of almost all carbon nanotubes, and the
electric field is concentrated at the tips of carbon nanotubes, so
as to locally concentrate electrons thereto, allowing the electron
emission at a high efficiency. In other words, the resistance
becomes lower to facilitate the electric current to flow easier,
thereby increasing the efficiency of electron emission.
[0068] Since one end of carbon nanotube is embedded in the metal
substrate, the carbon nanotubes are immobilized within the metal
substrate, thereby increasing the fixing force between the carbon
nanotubes and the metal substrate to reduce the probability of
dropout of the carbon nanotubes and to ultimately increase the
durability.
[0069] By transplanting the well aligned carbon nanotubes orderly
grown on a silicon substrate into a metal substrate, the silicon
substrate can be reused, so that a growth substrate comprising
expensive silicon can be used for a plurality of cycles, allowing
the reduction of manufacturing cost.
[0070] The carbon nanotube manufacturing method in accordance with
the third aspect of the present invention comprises:
[0071] a catalyst film formation step (e.g., catalyst film forming
apparatus 200, step S302) for forming a catalyst film consisted of
a predetermined catalyst on the surface of a predetermined growth
substrate;
[0072] an aligned growth step (e.g., an aligned growth apparatus
300, step S303) for causing a catalytic reaction between said
catalyst forming said catalyst film formed in said catalyst film
formation step and the vaporized gas of a predetermined
carbon-containing compound, to thereby cause a plurality of well
aligned carbon nanotubes to be orderly grown quasi-vertically on
the surface of said growth substrate;
[0073] a metal film vapor deposition step (e.g., a metal film vapor
deposition apparatus 700, step S304) for vapor depositing a layer
of predetermined metal film on the side having the tips of said
well aligned carbon nanotubes grown in said aligned growth
step;
[0074] a metal layer formation step (e.g., a metal layer plating
apparatus 800, step S305) for forming a predetermined metal layer
on said metal film formed in said metal film vapor deposition step;
and
[0075] a substrate separation step (e.g., a substrate separator
apparatus 600, step S306) for separating said carbon nanotubes from
said growth substrate.
[0076] In accordance with the carbon nanotube manufacturing method
of the third aspect of the present invention, the catalyst film
formation step in the carbon nanotube manufacturing method forms a
catalyst film on the surface of the predetermined growth substrate,
the aligned growth step causes a catalytic reaction between the
catalyst forming the catalyst film and the vaporized gas of the
predetermined carbon-containing compound to thereby cause a
plurality of well aligned carbon nanotubes to be orderly grown
quasi-vertically on the surface of the metal substrate through the
growth film, the metal film vapor deposition step vapor deposits a
layer of a predetermined metal film on the side having the tips of
carbon nanotubes, the metal layer formation step forms a
predetermined metal layer on the metal film, the substrate
separation step separates the carbon nanotubes from the growth
substrate, to cause well aligned carbon nanotubes to be orderly
grown.
[0077] In other words, the catalytic reaction between the catalyst
forming the catalyst film and the vaporized gas of a predetermined
carbon-containing compound causes the aligned growth of a plurality
of carbon nanotubes quasi-vertically on the surface of the growth
substrate, allowing the manufacture of the carbon nanotubes.
Consequently, the well aligned carbon nanotubes can be manufactured
with easier maintenance and control than the previous method of
formation of carbon nanotubes by dipping a silicon substrate in an
alcohol solution.
[0078] Since a plurality of carbon nanotubes manufactured in this
manner have one end being embedded in the metal substrate and are
implanted quasi-vertically on the surface of the metal substrate,
almost all of the carbon nanotubes are well aligned in the
longitudinal direction and are arranged in a quasi-parallel
manner.
[0079] The growth substrate is a substrate formed from a material
for suitably growing carbon nanotubes. Such materials for suitably
growing carbon nanotubes include among others silicon (Si) and
silicon compounds such as for example silicon carbide (SiC).
[0080] The catalyst film is a material which is necessary for the
aligned growth of carbon nanotubes and which promotes the growth.
The materials for the catalyst film include such as iron, iron
oxide, cobalt, and nickel.
[0081] With the plurality of well aligned carbon nanotubes orderly
arranged as such, an electric field can be applied in the
longitudinal direction of almost all carbon nanotubes, and the
electric field is concentrated at the tips of carbon nanotubes, so
as to locally concentrate electrons thereto, allowing the electron
emission at a high efficiency. In other word, the resistance
becomes lower to facilitate the electric current to flow easier,
thereby increasing the efficiency of electron emission.
[0082] Since one end of each carbon nanotube is embedded in the
metal film of the metal substrate, the carbon nanotubes are
immobilized within the metal substrate, thereby increasing the
fixing force between the carbon nanotubes and the metal substrate
to reduce the probability of dropout of the carbon nanotubes,
ultimately increasing the durability.
[0083] By transplanting the well aligned carbon nanotubes orderly
grown on a silicon substrate into a metal substrate, the growth
substrate can be reused, so that the growth substrate comprising
expensive silicon can be reused for a plurality of cycles, allowing
the reduction of manufacturing cost.
[0084] In addition, in the carbon nanotube manufacturing method in
accordance with the present invention, the method may comprise:
[0085] a second step of aligned growth (e.g., the step shown in
FIGS. 18 (b) and 18 (d), where the aligned carbon nanotubes are
orderly grown by the aligned growth apparatus 300) for causing the
aligned growth of said carbon nanotubes separated from said growth
substrate in said substrate separation step;
[0086] a second step of metal layer formation (e.g., the step shown
in FIGS. 18 (c) and 18 (e), where the metal layer is formed by the
metal layer plating apparatus 800) for forming a predetermined
metal layer on the side of well aligned carbon nanotubes orderly
grown in said second step of aligned growth and on the surface of
said metal film in which the rear end of each said carbon nanotubes
is embedded;
[0087] a metal layer slicing step (e.g., the step shown in FIG. 18
(g)) for slicing said metal layer formed and laminated in said
second step of metal layer formation in a direction perpendicular
to the direction of aligned growth of said carbon nanotubes to
thereby form a slice having a predetermined thickness; and
[0088] a metal layer removal step (e.g., the step shown in FIGS. 18
(h) and 18 (i)) for removing a predetermined amount of metal layer
of said slice formed in said metal layer slicing step in the
direction of aligned growth of said carbon nanotubes to thereby
expose a predetermined amount of said carbon nanotubes.
[0089] The metal layer which is laminated and formed by repeating
the aligned growth of the carbon nanotubes and the metal layer
formation is sliced in the direction perpendicular to the direction
of the aligned growth of the carbon nanotubes in the metal layer
slicing step to provide a slice having a predetermined thickness,
and a predetermined amount of metal layer of the slice is removed
in the direction of the aligned growth of the carbon nanotubes in
the metal layer removal step to expose a predetermined amount of
carbon nanotubes, thereby allowing the manufacture of well aligned
carbon nanotubes.
[0090] In particular, the carbon nanotubes which are disposed in
the metal film (metal layer) and which are formed in the substrate
separation step are used as the seeds for growing well aligned
carbon nanotubes, so that carbon nanotubes can be manufactured
without using any growth substrate comprising expensive silicon,
thereby allowing the reduction of manufacturing cost.
[0091] In the carbon nanotube manufacturing method in accordance
with the present invention,
[0092] said aligned growth step may comprise:
[0093] an ionizing step (for example, a first step) for ionizing
the vaporized gas of a predetermined carbon-containing
compound;
[0094] an electric field application step (for example, a second
step) for applying an electric field to the vaporized gas of said
carbon-containing compound, the vaporized gas being ionized in said
ionizing step; and
[0095] a heating step (for example, a third step) for heating said
metal substrate or said growth substrate, and
[0096] wherein, in said electric field application step, an
electric field may be applied to the vaporized gas of said
carbon-containing compound to bring the vaporized gas of said
carbon-containing compound into contact with said metal substrate
or said growth substrate, to ultimately cause a plurality of well
aligned carbon nanotubes to be grown quasi-vertically on the
surface of said metal substrate or said growth substrate.
[0097] In the aligned growth step in the carbon nanotube
manufacturing method, by applying an electric field in the electric
field application step to the vaporized gas of the predetermined
carbon-containing compound, the vaporized gas being ionized in the
ionizing step, the vaporized gas of the predetermined
carbon-containing compound is brought into contact with said metal
substrate or said growth substrate heated in the heating step, to
thereby cause the aligned growth of a plurality of carbon nanotubes
quasi-vertically on the surface of the metal substrate or growth
substrate.
[0098] More specifically, the vaporized gas of a predetermined
carbon-containing compound, the vaporized gas being ionized, is
brought into contact with the heated metal substrate or growth
substrate due to the Coulomb force of the electric field to thereby
react to form carbon nanotubes. The carbon nanotubes formed in this
manner are alignedly grown in the direction of the electric field
by the effect of the electric field, allowing the manufacture of
well aligned carbon nanotubes.
BRIEF DESCRIPTION OF THE DRAWINGS
[0099] FIG. 1 shows a schematic block diagram illustrating a carbon
nanotube manufacturing apparatus in accordance with the first
embodiment of the present invention;
[0100] FIG. 2 shows a schematic diagram illustrating the aligned
growth apparatus in the carbon nanotube manufacturing apparatus in
accordance with the present invention;
[0101] FIG. 3 shows a flow diagram illustrating the process steps
of carbon nanotube manufacturing method in accordance with the
first embodiment of the present invention;
[0102] FIG. 4 shows schematic diagrams illustrating the
corresponding steps shown in FIG. 3;
[0103] FIG. 5 shows a schematic diagram illustrating a negative ion
generator in the aligned growth apparatus;
[0104] FIG. 6 shows a schematic diagram illustrating an electric
field generator in the aligned growth apparatus;
[0105] FIG. 7 shows a schematic diagram illustrating a high
frequency heater in the aligned growth apparatus;
[0106] FIG. 8 shows a schematic diagram illustrating the aligned
growth of carbon nanotubes;
[0107] FIG. 9 shows a schematic block diagram illustrating a carbon
nanotube manufacturing apparatus in accordance with the second
embodiment of the present invention;
[0108] FIG. 10 shows a flow diagram illustrating the process steps
of carbon nanotube manufacturing method in accordance with the
second embodiment of the present invention;
[0109] FIG. 11 shows schematic diagrams illustrating the
corresponding steps shown in FIG. 10;
[0110] FIG. 12 shows a schematic diagram illustrating the
manufacturing steps of carbon nanotubes in accordance with another
example of the second embodiment of the present invention;
[0111] FIG. 13 shows a schematic diagram illustrating a member with
the carbon nanotubes protruding from both sides of the metal
substrate while extending through the metal substrate. FIG. 13 (a)
shows the state prior to the protrusion, and FIG. 13 (b) shows the
state after the protrusion;
[0112] FIG. 14 shows a schematic diagram illustrating the usage of
carbon nanotube containing member shown in FIG. 13 (b);
[0113] FIG. 15 shows a schematic block diagram illustrating a
carbon nanotube manufacturing apparatus in accordance with the
third embodiment of the present invention;
[0114] FIG. 16 shows a flow diagram illustrating the manufacturing
steps of carbon nanotube manufacturing method in accordance with
the third embodiment of the present invention;
[0115] FIG. 17 shows schematic diagrams corresponding to the
manufacturing steps shown in FIG. 16;
[0116] FIG. 18 shows a schematic diagram illustrating the
manufacturing steps of the carbon nanotube manufacturing method in
accordance with the fourth embodiment of the present invention;
and
[0117] FIG. 19 shows a schematic diagram illustrating the
manufacturing steps of the carbon nanotube manufacturing method in
accordance with the fourth embodiment of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0118] A detailed description of preferred embodiments of the
present invention are described herein below with reference to the
accompanying drawings in FIG. 1 to FIG. 19.
First Embodiment
[0119] FIG. 1 shows a schematic block diagram illustrating a carbon
nanotube manufacturing apparatus in accordance with the first
embodiment of the present invention.
[0120] As shown in FIG. 1, a carbon nanotube manufacturing
apparatus 1000 comprises a growth film forming apparatus 100 for
forming a silicon film 2, which is a growth film, as a silicon
layer on the surface of a metal substrate 1, a catalyst film
forming apparatus 200 for forming a catalyst film 3 on the surface
of the silicon film 2, an aligned growth apparatus 300 for causing
an aligned growth of a plurality of carbon nanotubes 4 . . . on the
metal substrate 1 through the silicon film 2 by making use of the
catalytic function of the catalyst film 3, a growth film removing
apparatus 400 for removing the silicon film 2 and thereby disposing
the carbon nanotubes 4 . . . on the surface of the metal substrate
1, and a substrate forming apparatus 500 for melting the metal
substrate 1, embedding one end 4a of each of the carbon nanotubes 4
disposed on the surface of the metal substrate 1 in the metal
substrate 1, and implanting the carbon nanotubes 4 . . . in the
metal substrate 1.
[0121] The growth film forming apparatus 100 may be for example a
vapor deposition apparatus, which is an apparatus for forming the
silicon film 2, used as the growth film, on the surface of the
metal substrate 1.
[0122] The metal substrate 1 may be a plate-like member formed from
a conductive material including such as copper, aluminium,
chromium, and stainless steel.
[0123] The silicon film 2 formed on the surface of the metal
substrate 1 by the growth film forming apparatus 100 may be a thin
film that is formed by vapor deposition of n-type silicon to have a
thickness in the order of a few nanometers to several hundreds
nanometers.
[0124] The growth film is a film to be formed in order for the
carbon nanotubes 4 . . . , as is described hereinafter, to be
suitably grown. Some exemplary materials which are used for the
suitable growth of the carbon nanotubes 4 . . . include among
others silicon (Si) and silicon compounds such as for example
silicon carbide (SiC).
[0125] The catalyst film forming apparatus 200 may be for example
one of the vacuum vapor deposition apparatus, molecular beam
epitaxy (MBE) apparatus, ion plating apparatus, ion beam epitaxy
apparatus, sputtering apparatus, and plating apparatus, which forms
a growth substrate 50 by forming a catalyst film 3 on the surface
of the silicon film 2 formed on the surface of the metal substrate
1.
[0126] The catalyst film 3 formed on the surface of the silicon
film 2 by the catalyst film forming apparatus 200 may be a thin
film formed by vapor depositing iron, iron oxide, cobalt, and
nickel at the thickness of the order of a few nanometers to several
hundreds nanometers.
[0127] These materials, such as iron, iron oxide, cobalt, and
nickel, forming the catalyst film 3 are the materials which are
necessary for the formation and the aligned growth of the carbon
nanotubes 4 . . . , as is described hereinafter, and which promote
the growth thereof.
[0128] The aligned growth apparatus 300 is an apparatus for causing
the aligned growth of a plurality of carbon nanotubes 4 . . . on
the growth substrate 50, which apparatus causes the aligned growth
of a plurality of carbon nanotubes 4 . . . on the metal substrate 1
through the silicon film 2.
[0129] The aligned growth apparatus 300, as shown in FIG. 2,
comprises a first chamber 301 and a second chamber 302, the
internal spaces of both of which communicate with each other
through a connecting part 303, and comprises a negative ion
generator 10 serving as an ionizing means provided in the first
chamber 301, an electric field generator 20 serving as an electric
field generating means provided in the second chamber 302, and a
high frequency heater 30 serving as a heating mans.
[0130] The negative ion generator 10 comprises a direct-current
power supply 11, a negative high-voltage electrode 12 connected to
the negative electrode of the direct-current power supply 11, a
ground electrode 13 connected to the positive electrode of the
direct-current power supply 11.
[0131] The negative high-voltage electrode 12 and the ground
electrode 13 are opposedly placed spaced apart at a predetermined
distance. There is a ground 14 between the positive electrode of
the direct-current power supply 11 and the ground electrode 13.
[0132] The negative ion generator 10, upon application of a
direct-current voltage across the negative high-voltage electrode
12 and the ground electrode 13 by the direct-current supplied from
the direct-current power supply 11, emits electrons from the
negative high-voltage electrode 12 toward the ground electrode
13.
[0133] The electric field generator 20 comprises a direct-current
power supply 21, a cathode electrode 22 connected to the negative
electrode of the direct-current power supply 21, and an anode
electrode 23 connected to the positive electrode of the
direct-current power supply 21.
[0134] The cathode electrode 22 and the anode electrode 23 are
opposedly disposed spaced apart at a predetermined distance.
[0135] The electric field generator 20, upon application of a
direct-current voltage between the cathode electrode 22 and the
anode electrode 23 by the direct-current supplied from the
direct-current power supply 21, generates an electric field which
extends from the upper surface of the anode electrode 23 toward the
lower surface of the cathode electrode 22.
[0136] The anode electrode 23, as is described hererinafter, has
also the function of a heater unit heated by the high frequency
heater 30, and is formed from a material comprising a lamination or
mixture of a magnetic substance and a conductive substance.
[0137] The anode electrode 23, in addition, as is described
hereinafter, also has a function of a sample holder for mounting
the growth substrate 50, in which the growth substrate 50 is
mounted on the surface of the anode electrode 23 with the surface
thereof opposing the cathode electrode 22.
[0138] The high frequency heater 30 comprises a high frequency
power supply 31 and a coil 32 connected to the high frequency power
supply 31.
[0139] The high frequency heater 30, upon application of
alternate-current voltage to the coil 32 by the alternate-current
supplied from the high frequency power supply 31, generates an
alternate-current magnetic field in the coil 32 and generates high
frequency electromagnetic waves around the coil 32.
[0140] The coil 32 of the high frequency heater 30 is disposed on
the lower surface side of the anode electrode 23 of the electric
field generator 20, which is the side opposing the cathode
electrode 22, with the center axis of the coil 32 being
perpendicular to the lower surface of the anode electrode 23. The
electromagnetic waves generated in the coil 32 disposed at this
location are adapted to be irradiated on the anode electrode 23
which is the heating unit.
[0141] The electromagnetic waves irradiated on the anode electrode
23 rapidly change their fluxes because the fluxes of the
electromagnetic waves are concentrated by the magnetic substance
included in the anode electrode 23. Due to the rapid change of
flux, an eddy current is generated in the conductive substance
included in the anode electrode 23. The eddy current flowing
through the anode electrode 23 generates heat in the anode
electrode 23 due to Joule heat to thereby increase the temperature
of the anode electrode 23.
[0142] The growth film removing apparatus 400 may be for example an
etching apparatus, which apparatus dissolves the silicon component
dipped in a silicon dissolving solution contained in the etching
apparatus. The silicon dissolving solution is a solution that
selectively dissolves silicon.
[0143] The growth film removing apparatus 400 dissolves the silicon
film 2 to dispose the carbon nanotubes 4 . . . having been disposed
on the surface of the silicon film 2 on the surface of the metal
substrate 1.
[0144] The substrate forming apparatus 500 is an apparatus for
example for heating and melting a substrate and for cooling and
solidifying the molten substrate.
[0145] The substrate forming apparatus 500 melts the metal
substrate 1 so as to cause one end 4a of each of the carbon
nanotubes 4 . . . disposed on the surface of the metal substrate 1
to be submerged to a predetermined depth and then cools and
solidifies the metal substrate 1, to thereby implant the carbon
nanotubes 4 . . . in the metal substrate 1.
[0146] The carbon nanotube manufacturing method by means of the
carbon nanotube manufacturing apparatus 1000 is described in
greater details herein below.
[0147] FIG. 3 shows a flow diagram illustrating the manufacturing
steps of the carbon nanotube manufacturing method in accordance
with the first embodiment of the present invention, and FIG. 4
shows schematic diagrams illustrating correspondingly the
manufacturing processes (steps) shown in FIG. 3.
[0148] As shown in FIG. 3, the carbon nanotube manufacturing method
in accordance with the first embodiment primarily comprises
following six processes (six steps): a metal substrate preparation
step (step S101) for preparing a metal substrate 1, a growth film
formation step (step S102) for forming a silicon film 2 serving as
the growth film on the surface of the metal substrate 1, a catalyst
film formation step (step S103) for forming a catalyst film 3 on
the surface of the formed silicon film 2, an aligned growth step
(step S104) for causing the aligned growth of the carbon nanotubes
4 . . . on the surface of the metal substrate 1 through the silicon
film 2 while the carbon nanotubes are trapping as the nuclei the
catalyst particles forming the formed catalyst film 3, a growth
film removal step (step S105) for removing the silicon film 2 to
dispose the carbon nanotubes 4 . . . on the surface of the metal
substrate 1, and a substrate formation step (step S106) for melting
the metal substrate 1 to embed one end 4a of each of the carbon
nanotubes 4 . . . disposed on the surface of the metal substrate 1
in the molten metal substrate 1 and thereafter solidifying the
metal substrate 1.
[0149] The metal substrate preparation step in step S101 is a step
for preparing the metal substrate 1 on which the carbon nanotubes 4
. . . are formed as shown in FIG. 4 (a).
[0150] The growth film formation step in step S102 is a step for
forming the silicon film 2 serving as the growth film on the
surface of the metal substrate 1 by means of the growth film
forming apparatus 100, as shown in FIG. 4 (b).
[0151] The catalyst film formation step in step S103 is a step for
further forming a catalyst film 3 on the surface of the silicon
film 2 by means of the catalyst film forming apparatus 200, as
shown in FIG. 4 (c). This step forms the growth substrate 50.
[0152] The aligned growth step in step S104 is a step for causing
the aligned growth of the carbon nanotubes 4 . . . on the surface
of the silicon film 2 by means of the aligned growth apparatus 300,
as shown in FIG. 4 (d).
[0153] It should be noted here that the carbon nanotubes 4 . . .
grow while trapping as the nuclei the particles of the substance
forming the catalyst film 3 as nuclei.
[0154] The aligned growth step (S104) in the aligned growth
apparatus 300 is described in greater details herein below.
[0155] The aligned growth step mainly comprises a first step where
the vaporized gas (vapor) of a predetermined carbon-containing
compound which is the raw material for forming the carbon nanotubes
is negatively charged and the vaporized gas is negatively ionized;
a second step where the vaporized gas of the carbon-containing
compound, the vaporized gas being negatively charged, is supplied
to between the anode electrode 23 and cathode electrode 22, with
the electric field being applied across these electrodes; and a
third step where the vaporized gas of carbon-containing compound,
the vaporized gas being negatively charged, comes into contact with
the growth substrate 50 mounted on the anode, electrode 23, to
thereby cause the aligned growth of carbon nanotubes 4 . . . .
[0156] The predetermined carbon-containing compound as the material
for forming the carbon nanotubes is for example an organic
substance containing carbon (C), and includes, for example,
methanol, ethanol, 1-butanol, 1-octanol, etc. In the present
embodiment, an example is described which uses methanol as the
predetermined carbon-containing compound (organic substance).
[0157] On the upper surface of the anode electrode 23 of the
electric field generator 20 serving as a sample stage, the silicon
film 2 having a catalyst film 3 formed in the catalyst film
formation step of the step S103 (growth substrate 50) is
mounted.
[0158] Then, the air in the first chamber 301, the second chamber
302, and the connecting part 303 of the aligned growth apparatus
300 shown in FIG. 2 is removed by means of a vacuum pump, and then
an inert gas (such as argon) is fed into the first chamber 301, the
second chamber 302, and the connecting part 303 to fill the
apparatus with the inert gas so as to perform the gas flushing.
[0159] Next, methanol vapor M . . . , which is a vaporized gas
obtained by heating or by placing under a high vacuum the methanol
stored in a storage tank not shown in the figure, is fed to the
first chamber 301.
[0160] The methanol vapor M . . . fed to the first chamber 301
passes between the negative high-voltage electrode 12 and the
ground electrode 13 of the negative ion generator 10, as shown in
FIG. 5. When the methanol vapor M . . . passes between the negative
high-voltage electrode 12 and the ground electrode 13 of the
negative ion generator 10, electrons emitted from the negative
high-voltage electrode 12 collide with the methanol vapor M . . .
to cause the methanol vapor M . . . to be negatively charged to
ultimately become methanol ions Mi . . . . Although negatively
charged methanol ions Mi . . . are drawn to the ground electrode
13, they are pushed out from the first chamber 301 by the methanol
vapor M . . . which follows. This is the first step.
[0161] The methanol ions Mi . . . then pass through the connecting
part 303 to second chamber 302.
[0162] Next, the methanol ions Mi . . . fed into the second chamber
302 passes between the cathode electrode 22 and the anode electrode
23 of the electric field generator 20, as shown in FIG. 6. During
this step, the electric field generator 20 applies an electric
field extending from the anode electrode 23 toward the cathode
electrode 22 (the electric field in the direction of the arrow A in
FIG. 6). This is the second step.
[0163] As shown in FIG. 7, the high frequency electromagnetic waves
output from the high frequency heater 30 generates an eddy current
in the anode electrode 23 to heat the anode electrode 23 to a high
temperature (for example, 600 to 1200 degrees centigrade). The
growth substrate 50 mounted on the upper surface of the anode
electrode 23 also is heated through the anode electrode 23 to a
similarly high temperature.
[0164] The methanol ions Mi . . . fed to between the cathode
electrode 22 and the anode electrode 23 of the electric field
generator 20 are negatively charged, so that the effect of electric
field extending from the anode electrode 23 to the cathode
electrode 22, namely the Coulomb force, draws ions toward the anode
electrode 23. The methanol ions Mi . . . drawn up to the growth
substrate 50 mounted on the anode electrode 23 come into contact
with the catalyst film 3 formed on the metal substrate 1 of the
growth substrate 50. Since the metal substrate 1 as well as the
catalyst film 3 of the growth substrate 50 are heated to a high
temperature (e.g., 600 to 1200 degrees centigrade) by the high
frequency heater 30 through the anode electrode 23, the methanol
ions Mi . . . are pyrolyzed on the growth substrate 50 (the
catalyst film 3). The reaction time of the pyrolysis is preferably
about thirty minutes, and the more preferable reaction time is not
less than thirty minutes. As shown in FIG. 8, the carbons contained
in the methanol ions Mi . . . are left behind on the metal
substrate 1 (the catalyst film 3) of the growth substrate 50, while
the water (H.sub.2O) and hydrogen (H.sub.2) produced during the
pyrolysis are exhausted out of the apparatus (the second chamber
102).
[0165] It should be noted here that the preferred condition for the
reaction efficiency is such that the methanol ions Mi . . . are
pyrolyzed on the surface of the growth substrate 50 and fed
according to the reaction rate of the formation of carbon nanotubes
4 . . . . It is also preferable in view of safety with respect to
the maintenance and control of the apparatus such that excess
methanol ions Mi . . . more than required are not supplied.
[0166] The Iterative repetition of pyrolysis of the methanol ions
Mi . . . provides the accumulation of carbons on the metal
substrate 1 (the catalyst film 3) of the growth substrate 50. The
accumulated carbons trap as catalyst the particles of iron and the
like, which form the catalyst film 3, to thereby form the carbon
nanotubes 4 . . . . This is the third step.
[0167] To induce the chemical reaction of the carbon with the
catalyst, the energy level of the electrons in the outermost shell
should be increased, so that the reaction under a high temperature
environment as have been described above (the carbon nanotube
formation step) is necessary.
[0168] The silicon film 2 of the growth substrate 50 on which the
carbon nanotubes 4 . . . are formed is positively charged by the
direct-current power supply 21 through the anode electrode 23, so
that the carbon nanotubes 4 . . . are also positively charged.
There is applied, between the cathode electrode 22 and the anode
electrode 23, an electric field extending from the anode electrode
23 to the cathode electrode 22 (the electric field in the direction
of the arrow A in FIG. 6 and in FIG. 8), the tips 4b of the carbon
nanotubes 4 . . . are drawn toward the upper side of the cathode
electrode 22. The effect of the electric field causes the carbon
nanotubes 4 . . . to be formed and grown while the tips 4b thereof
are being pulled upwardly. This causes the aligned growth of the
carbon nanotubes 4 . . . quasi-vertically from the growth substrate
50. The carbon nanotubes 4 . . . , during this step, grow while
trapping the catalyst particles which form the catalyst film 3.
[0169] Since the direction of the aligned growth of the carbon
nanotubes 4 . . . , is in the direction of the electric field
extending from the anode electrode 23 toward the cathode electrode
22, the carbon nanotubes 4 . . . are aligned and grown in the
direction normal to the metal substrate 1 of the growth substrate
50, if the growth substrate 50 is disposed perpendicularly to the
electric field.
[0170] As can be seen from the foregoing, the aligned growth of the
carbon nanotubes 4 . . . is effectuated on the metal substrate 1 of
the growth substrate 50 in step S104.
[0171] The growth film removal step in step S105 is a step for
removing the silicon film 2 serving as the growth film by the
growth film removing apparatus 400, as shown in FIG. 4 (e).
[0172] When the silicon film 2 is dissolved and removed by the
silicon dissolving solution contained in the growth film removing
apparatus 400, the carbon nanotubes 4 . . . formed on the metal
substrate 1 through the silicon film 2 are arranged and disposed on
the surface of the metal substrate 1.
[0173] By slowly dissolving the silicon film 2 with the silicon
dissolving solution as described above, the carbon nanotubes 4 . .
. on the silicon film 2 gradually fall and settle on the metal
substrate 1, so that the carbon nanotubes 4 . . . are arranged and
disposed on the surface of the metal substrate 1, with the form of
aligned growth being maintained.
[0174] The substrate formation step in the step S106 is a step for
embedding one end 4a of each of the carbon nanotubes 4 . . .
disposed on the surface of the metal substrate 1 in the metal
substrate 1 to implant the carbon nanotubes 4 . . . in the metal
substrate 1, as shown in FIG. 4 (f), by the substrate forming
apparatus 500.
[0175] When the metal substrate 1 is formed from for example copper
(Cu), the substrate forming apparatus 500 heats and melts the metal
substrate 1 to its melting point (approximately 1084 degrees
centigrade) or over, so as to submerge and embed to a predetermined
depth one end 4a of each of the carbon nanotubes 4 . . . disposed
on the surface of the metal substrate 1. Then the substrate forming
apparatus 500 cools the metal substrate 1 and solidifies the metal
substrate 1 to fix and implant the carbon nanotubes 4 . . . in the
metal substrate 1.
[0176] The carbon nanotubes 4 . . . implanted on the metal
substrate 1 have a diameter of a few nanometers to over ten
nanometers and a length of 1 micrometer to several tens
micrometers, and they are formed in the order of a million to ten
billions per each square millimeter (mm.sup.2).
[0177] As can be appreciated from the foregoing description, the
carbon nanotube manufacturing method by using the carbon nanotube
manufacturing apparatus 1000 in accordance with the present
invention, the methanol ions Mi . . . , which are obtained by
negatively charging methanol vapor M . . . by the negative ion
generator 10, are pyrolyzed on the surface of the growth substrate
50 placed within an electric field, so as to cause the aligned
growth of the carbon nanotubes 4 . . . on the surface of the metal
substrate 1 of the growth substrate 50 to thereby form and
manufacture the carbon nanotubes 4 . . . . Thus, well aligned
carbon nanotubes 4 . . . can be arranged and disposed on the metal
substrate 1.
[0178] In accordance with the present invention, the formation of
carbon nanotubes within an electric field easily allows the well
aligned growth of carbon nanotubes.
[0179] Methanol, the raw material for carbon nanotubes, is stored
in a storage reservoir not shown in the figure. Only the methanol
ions Mi . . . required for forming the carbon nanotubes 4 . . . by
pyrolysis are fed to the anode electrode 23 and the growth
substrate 50 both having been heated to a high temperature, so that
the maintenance and control of the apparatus is facilitated in
preventing the explosion and fire caused by the excessively fed
methanol. In particular, since the gas within the apparatus is
replaced with an inert gas, methanol is never mixed with air
(oxygen), making it much safer than ever.
[0180] The methanol ions Mi . . . to be pyrolyzed on the surface of
the growth substrate 50 are fed according to the reaction rate of
forming the carbon nanotubes 4 . . . allowing the carbon nanotubes
4 . . . to be manufactured at a high production efficiency.
[0181] The carbon nanotubes 4 . . . manufactured in this manner
have one ends 4a each being embedded in the metal substrate 1, and
are implanted quasi-vertically on the surface of the metal
substrate 1, so that the well aligned carbon nanotubes 4 . . . are
arranged in quasi-parallel to the longitudinal direction. With a
plurality of carbon nanotubes 4 . . . being well aligned as such,
an electric field can be applied in the longitudinal direction of
almost all of the carbon nanotubes 4 . . . , and the electric field
is concentrated at the tips of the carbon nanotubes 4 . . . , thus
the electrons are locally concentrated thereto, allowing the
electron emission at a high efficiency and lowering the resistance
value to facilitate the electric current to flow easily, to thereby
increase the electron emission efficiency. In other words, the
carbon nanotubes 4 . . . can be suitably used for such as the
electron emission electrodes which emits electrons.
Second Embodiment
[0182] The second embodiment in accordance with the present
invention is described in greater details herein below. The same
reference numerals are used for the same elements as those of the
first embodiment, and only the different elements are described in
details.
[0183] FIG. 9 shows a schematic block diagram illustrating a carbon
nanotube manufacturing apparatus in accordance with the second
embodiment of the present invention.
[0184] An shown in FIG. 9, the carbon nanotube manufacturing
apparatus 2000 includes a catalyst film forming apparatus 200 for
forming a catalyst film 3 on the surface of a silicon substrate 5,
which is a silicon layer, to form a growth substrate 55, an aligned
growth apparatus 300 for using the catalytic function of the
catalyst film 3 to cause the aligned growth of a plurality of
carbon nanotubes 4 . . . on the growth substrate 55 (the silicon
substrate 5), a substrate forming apparatus 550 for inserting the
tips 4b of the carbon nanotubes 4 . . . alignedly grown on the
surface of the growth substrate 55 (the silicon substrate 5) into
the molten metal substrate 1A to implant the carbon nanotubes 4 . .
. in the metal substrate 1A, and a substrate separating apparatus
600 for separating the carbon nanotubes 4 . . . from the silicon
substrate 5.
[0185] The substrate forming apparatus 550 is an apparatus for
heating and melting the metal substrate 1A and for cooling and
solidifying the metal substrate 1A, as well as an apparatus for
embedding the tips 4b of the carbon nanotubes 4 . . . grown on the
surface of the silicon substrate 5 in the molten metal substrate 1A
to implant the carbon nanotubes 4 . . . in the metal substrate
1A.
[0186] The substrate separating apparatus 600 is an apparatus for
separating the carbon nanotubes 4 . . . from the silicon substrate
5, and for disposing the carbon nanotubes 4 . . . on the metal
substrate 1A.
[0187] The carbon nanotube manufacturing method in the carbon
nanotube manufacturing apparatus 2000 is described in greater
details herein below.
[0188] FIG. 10 shows a schematic flow diagram illustrating the
manufacturing steps of the carbon nanotube manufacturing method in
accordance with the second embodiment of the present invention, and
FIG. 11 shows a series of schematic diagrams corresponding to the
manufacturing steps shown in FIG. 10.
[0189] As shown in FIG. 10, the carbon nanotube manufacturing
method in accordance with the second embodiment mainly comprises
following five processes (five steps): a growth substrate
preparation step (step S201) for preparing a silicon substrate 5, a
catalyst film formation step (step S202) for forming a catalyst
film 3 on the silicon substrate 5, an aligned growth step (step
S203) for causing the aligned growth of the carbon nanotubes 4 . .
. on the surface of the silicon substrate 5 while the carbon
nanotubes are trapping as the nuclei the catalyst particles which
form the formed catalyst film 3, a substrate forming step (step
S204) for inserting the tips 4b of the carbon nanotubes 4 . . .
alignedly grown on the surface of the silicon substrate 5 into the
molten metal substrate 1A and thereafter solidifying the metal
substrate 1A, and a substrate separation step (step S205) for
separating the carbon nanotubes 4 . . . from the silicon substrate
5.
[0190] The growth substrate preparation step in step S201 is a step
for preparing the silicon substrate 5 for forming the carbon
nanotubes 4 . . . , as shown in FIG. 11 (a).
[0191] The silicon substrate 5 may be a plate-like member made of
for example an n-type silicon.
[0192] The catalyst film formation step in step S202 is a step for
forming the catalyst film 3 on the surface of the silicon substrate
5 by the catalyst film forming apparatus 200, to thereby form the
growth substrate 55, as shown in FIG. 11 (b).
[0193] The aligned growth step in step S203 is a step for causing
the aligned growth of the carbon nanotubes 4 . . . on the surface
of the silicon substrate 5 of the growth substrate 55 by the
aligned growth apparatus 300, as shown in FIG. 11 (c).
[0194] The carbon nanotubes 4 . . . are alignedly grown and formed
by the aligned growth apparatus 300 shown in FIG. 2.
[0195] The aligned growth method of the carbon nanotubes 4 . . . in
the aligned growth step is generally similar to the step S104 of
the first embodiment, and the aligned growth apparatus 300 also is
identical, so that the detailed description is omitted here.
[0196] The substrate formation step in step S204 is a step for
inserting the tips 4b of the carbon nanotubes 4 . . . alignedly
grown on the surface of the silicon substrate 5 into the metal
substrate 1A and then solidifying the metal substrate 1A
thereafter, as shown in FIG. 11 (d), by the substrate forming
apparatus 550.
[0197] The metal substrate 1A may be made of a conductive material
such as for example copper, aluminum, stainless steel, and the
like.
[0198] When the metal substrate 1A is made of for example copper,
the substrate forming apparatus 550 heats the metal substrate 1A to
its melting point (approximately 1084 degrees centigrade) or over
and melts it, so as to submerge the tips 4b of the carbon nanotubes
4 . . . alignedly grow on the surface of the silicon substrate 5 in
the aligned growth step (S203) to a predetermined depth. Then, the
substrate forming apparatus 550 cools the metal substrate 1A and
solidifies the metal substrate 1A to thereby fix and implant the
carbon nanotubes 4 . . . in the metal substrate 1A. This substrate
formation step may be also called as a carbon nanotube implanting
step, and the substrate forming apparatus 550 may be also called as
a carbon nanotube implanting apparatus.
[0199] The substrate separation step in step S205 is a step for
separating the carbon nanotubes 4 . . . from the silicon substrate
5 by the substrate separating apparatus 600 to thereby arrange and
dispose the carbon nanotubes 4 . . . on the metal substrate 1A, as
shown in FIG. 11 (e).
[0200] As for the method of separating the carbon nanotubes 4 . . .
from the silicon substrate 5, there is a method, for instance, in
which the silicon substrate 5 is heated by the heater device
serving as the substrate separating apparatus 600, to cause the
carbon nanotubes 4 . . . to be pulled out of the silicon substrate
5.
[0201] As for the method of separating the carbon nanotubes 4 . . .
from the silicon substrate 5, there is a method, for instance, in
which a laser radiation device serving as the substrate separating
apparatus 600 irradiates a laser beam to the carbon nanotubes 4 . .
. at a point near the silicon substrate 5, to thereby cut the
carbon nanotubes 4 . . . .
[0202] As for the method of separating the carbon nanotubes 4 . . .
from the silicon substrate 5, there is a method, for instance, in
which a magnet (electromagnet or permanent magnet) serving as the
substrate separating apparatus 600 may be used to pull the iron
dispersed in the silicon substrate 5 as the catalyst or the iron
dispersed for the separation toward the magnet, to thereby exert a
force to the silicon substrate 5 to separate the carbon nanotubes 4
. . . therefrom.
[0203] The carbon nanotubes 4 . . . implanted in the metal
substrate 1A have a diameter of a few nanometers to over ten
nanometers and a length of 1 micrometer to several tens
micrometers, and they are formed in the order of a million to ten
billions per each square millimeter (mm.sup.2).
[0204] In accordance with the carbon nanotube manufacturing method
of the present embodiment, the negatively charged methanol ions Mi
. . . obtained by negatively charging the methanol vapor M . . .
using the negative ion generator 10 are pyrolyzed on the surface of
the silicon substrate 5 of the growth substrate 55 placed within an
electric field, to cause an aligned growth of the carbon nanotubes
4 . . . on the surface of the silicon substrate 5, then implant
them in the metal substrate 1A to form and manufacture the carbon
nanotubes 4 . . . . In accordance with the present invention, the
formation of carbon nanotubes within an electric field easily
allows the wall aligned growth of the carbon nanotubes.
[0205] In particular, since the carbon nanotubes 4 . . . alignedly
grown on the surface of the silicon substrate 5 are implanted and
transplanted in the metal substrate 1A, an expensive silicon
substrate 5 can be reused for a plurality of cycles, allowing the
reduction of manufacturing cost.
[0206] The methanol ions Mi . . . to be pyrolyzed on the surface of
the silicon substrate 5 of the growth substrate 50 are fed
according to the reaction rate of formation of the carbon nanotubes
4 . . . , allowing the manufacturing of carbon nanotubes 4 . . . at
a high production efficiency, while on the other hand since only
the required amount of methanol ions Mi . . . for forming the
carbon nanotubes 4 . . . is fed to the anode electrode 23 and the
metal substrate 1 both having been heated to a high temperature, it
is safer and easier with respect to the maintenance and control of
the apparatus in preventing the explosion and fire caused by the
excessively fed methanol.
[0207] Another modification of the second embodiment is described
in greater details herein below.
[0208] FIG. 12 shows a schematic diagram illustrating the carbon
nanotube manufacturing steps in accordance with another
modification of the second embodiment.
[0209] As shown in FIG. 12, the carbon nanotube manufacturing
method in accordance with the another modification of the second
embodiment mainly comprises following seven steps: a growth
substrate preparation step (FIG. 12 (a)) for preparing the silicon
substrate 5, a catalyst film formation step (FIG. 12 (b)) for
forming a catalyst film 3 on the surface of the silicon substrate
5, an aligned growth step (FIG. 12 (c)) for causing an aligned
growth of the carbon nanotubes 4 . . . on the surface of the
silicon substrate 5 while the carbon nanotubes 4 . . . are trapping
as the nuclei the catalyst particles which form the formed catalyst
film 3, a metal film vapor deposition step (FIG. 12 (d)) for vapor
depositing a metal film 111a that covers around the sides of the
alignedly grown carbon nanotubes 4 . . . , a substrate formation
step (FIG. 12 (e)) for inserting the tips 4b of the carbon
nanotubes 4 . . . into the molten metal substrate 1A and then
solidifying the metal substrate 1A thereafter, a substrate
separation step (FIG. 12 (f)) for separating the carbon nanotubes 4
. . . from the silicon substrate 5, and metal film removal step
(FIG. 12(g)) for removing the metal film 111a.
[0210] The growth substrate preparation step shown in FIG. 12 (a)
is a step for preparing the silicon substrate 5 on which the carbon
nanotubes 4 . . . is formed.
[0211] The silicon substrate 5 may be a plate-like member made of
for example an n-type silicon.
[0212] The catalyst film formation step shown in FIG. 12 (b) is a
step for forming the catalyst film 3 on the surface of the silicon
substrate 5 by the catalyst film forming apparatus 200, to thereby
form the growth substrate 55.
[0213] The aligned growth step shown in FIG. 12 (c) is a step for
causing the aligned growth of the carbon nanotubes 4 . . . on the
surface of the silicon substrate 5 of the growth substrate 55 by
the aligned growth apparatus 300.
[0214] The carbon nanotubes 4 . . . are alignedly grown and formed
by the aligned growth apparatus 300 shown in FIG. 2.
[0215] Since the method of aligned growth of the carbon nanotubes 4
. . . in the aligned growth step is generally similar to the step
S104 of the first embodiment and the aligned growth apparatus 300
is identical with that used therein, the detailed description is
omitted here.
[0216] The metal film vapor deposition step shown in FIG. 12 (d) is
a step for vapor depositing a metal film 111a around the sides of
the carbon nanotubes 4 . . . as well as on the surface of the
silicon substrate 5 by using for example a metal film vapor
deposition apparatus. The metal film deposition apparatus is
similar to the catalyst film forming apparatus 200, and may be for
example one of the vacuum vapor deposition apparatus, molecular
beam epitaxy (MBE) apparatus, ion plating apparatus, ion beam
epitaxy apparatus, sputtering apparatus, and plating apparatus.
[0217] The metal film vapor deposition apparatus deposits, on the
surface side of the silicon substrate 5, a metal film 111a having a
thickness of a few nanometers to several hundreds nanometers and
being made of a conductive metal including such as for example
aluminum, copper, silver, and nickel.
[0218] The metal film 111a does not completely cover the carbon
nanotubes 4 . . . , rather the tips 4b of the carbon nanotubes 4 .
. . protrude from the surface of the metal film 111a.
[0219] The substrate formation step shown in FIG. 12 (e) uses the
substrate forming apparatus 550 to insert the tips 4b of the carbon
nanotubes 4 . . . alignedly grown on the surface of the silicon
substrate 5 into the molten metal substrate 1A, then to solidify
the metal substrate 1A to implant the carbon nanotubes 4 . . . in
the metal substrate 1A. The metal substrate 1A is made of a
conductive material including such as for example copper, aluminum,
chrome, stainless steel, and the like.
[0220] The metal film vapor deposition step for covering the carbon
nanotubes 4 . . . with the metal film 111a is preliminarily
employed so as to facilitate the bonding of the carbon nanotubes 4
. . . to the molten metal substrate 1A. This phenomenon is similar
to the so-called wetting phenomenon in such as soldering. Once,
even when it is only once, a metal is attached on the carbon
nanotubes 4 . . . due to such as vapor deposition, the molten metal
substrate 1A is facilitated to easily bond to the carbon nanotubes
4 . . . . By making use of this phenomenon the carbon nanotubes 4 .
. . are suitably implanted in the metal substrate 1A.
[0221] The substrate separation step shown in FIG. 12 (f) is a step
for separating the carbon nanotubes 4 . . . from the silicon
substrate 5 to dispose the carbon nanotubes 4 . . . on the metal
substrate 1A by using the substrate separating apparatus 600. The
step is similar to that in the second embodiment and the detailed
description is omitted here.
[0222] The metal film removal step shown in FIG. 12 (g) is a step
for removing the metal file 111a by using a metal film remover
apparatus.
[0223] The metal film removing apparatus is for example an
apparatus for melting the metal film 111a, which apparatus
selectively melts the metal film 111a by using a metal film
dissolving solution (such as for example hydrochloric acid, nitric
acid, sulfuric acid) stored in the metal film removing
apparatus.
[0224] As for the metal film dissolving solution, it is preferable
to use a dissolving solution which selectively dissolves the metal
film 111a according to the combination of the metal which forms the
metal substrate 1A and the metal which forms the metal film 111a.
It is also preferable to prepare the dissolving solution by paying
a due attention to the metal which forms the metal film 111a and
the metal which forms the metal substrate 1A.
[0225] The carbon nanotube 4 . . . implanted in the metal substrate
1A have for example a diameter of a few nanometers to over ten
nanometers and a length of 1 micrometer to several tens
micrometers, and they are formed in the order of a million to ten
billions per each square millimeter (mm.sup.2).
[0226] The well aligned carbon nanotubes can be easily grown by
such a carbon nanotube manufacturing method as has been described
above. The well aligned carbon nanotubes 4 . . . can be orderly
arranged and disposed on the metal substrate 1A.
[0227] Although the metal substrate 1A shown in FIG. 12 (g) has the
carbon nanotubes 4 . . . being disposed on one side of the metal
substrate 1A with the carbon nanotubes 4 . . . being exposed from
the one side, the carbon nanotubes 4 . . . may also be formed on
both sides of the metal substrate 1A with the carbon nanotubes 4 .
. . being exposed from the both sides.
[0228] For instance, a member having carbon nanotubes 4 . . .
embedded across two layers of metal substrate 1A and metal film
111a shown in FIG. 13 (a), as has been formed in the substrate
separation step (c.f., FIG. 12 (f)) of the carbon nanotube
manufacturing method in accordance with the another modification of
the second embodiment of the present invention, can be dipped in a
predetermined dissolving solution (for example, hydrochloric acid,
nitric acid, sulfuric acid) to dissolve a predetermined amount of
the metal substrate 1A and the metal film 111a to obtain the carbon
nanotubes 4 . . . being exposed from both sides of the metal
substrate 1A, as shown in FIG. 13 (b). The carbon nanotubes 4 . . .
extend through the metal substrate 1A to be exposed from both sides
thereof.
[0229] The extent of exposure of the carbon nanotubes 4 . . . from
the surface of the metal substrate 1A may be adjusted by the degree
of dissolving the metal substrate 1A and metal film 111a. The
carbon nanotubes 4 . . . protrude and are exposed by a suitable
length from the surface of the metal substrate 1A.
[0230] The dissolving solution may be a solution which dissolves
both the metal substrate 1A and the metal film 111a, or may be a
series of solutions each of which dissolves the metal substrate 1A
and metal film 111a respectively.
[0231] The application field of the member having carbon nanotubes
4 . . . being exposed from both sides of the metal substrate 1A as
shown in FIG. 13 (b) is described herein below.
[0232] The carbon nanotube 4 is known as a material which emits
electrons e within an electric field, and may be used as the
electron emission electrode.
[0233] The phenomenon of electron emission is generally referred to
as electron field emission, in which, when a strong electric field
is applied to a solid surface, the potential barrier of the surface
that traps the electrons within the solid body becomes lower and
thinner, so that the electrons are emitted into a vacuum due to the
tunneling effect. In particular, when a substance having a small
radius of curvature is placed in an electric field, the charges are
concentrated at the pointed area having a smaller radius of
curvature, facilitating the emission of electrons. This phenomenon
is referred to as tip concentration phenomenon of charges, which is
well known in the field of discharge engineering. A substance
having a diamond structure in particular has a negative electron
affinity, being capable of facilitating the emission of conduction
electrons.
[0234] Substances having such diamond structure include a substance
mainly formed from carbon atoms, such as carbon nanotubes 4. Since
the carbon nanotube 4 is a substance having a small diameter, the
electrons within a carbon nanotube 4 are concentrated at the area
nearest to the positive potential due to the Coulomb force, because
of the tip concentration phenomenon of charges. If the electric
field applied to the carbon nanotube 4 is larger than the threshold
value of electron emission, then a part of electrons having being
concentrated at the tip of carbon nanotube 4 having a smaller
radius of curvature are emitted into the space. Since the carbon
nanotube 4 is an extremely thin tube-like substance having a
diameter of a few nanometers, electrons can be emitted even in a
weak electric field.
[0235] The amount of electron emission from the carbon nanotubes 4
increases exponentially in proportion to their surface temperature.
To cause a large amount of electrons to be emitted from the carbon
nanotubes 4, the temperature of the carbon nanotubes 4 needs to be
raised by means of a heat source H as shown in FIG. 14, so as to
increase the energy of the electrons inside the carbon nanotubes 4.
Since the heat is conducted extremely fast through the carbon
nanotubes 4, the electron emission efficiency can be increased by
directly conducting the heat to the carbon nanotubes 4 than by
indirectly conducting the thermal energy to the carbon nanotubes 4
from the heat source H through the metal film 111a or the metal
substrate 1A. Accordingly, the most suitable structure for the
electron emission electrode is such that the carbon nanotubes 4 are
exposed and protruding from both sides of the electrodes while
extending therethrough, as shown in FIG. 14.
[0236] As shown in FIG. 14, when the carbon nanotubes 4 being
exposed from the surface of the metal film 111a is directly heated
by a heat source H to emit electrons from the carbon nanotubes 4
being exposed from the surface of the metal substrate 1A, the
thermal energy is converted to the kinetic energy of electrons at a
higher efficiency. To sustain the electron emission from the tips
of the carbon nanotubes 4, it is required for the electrons to be
supplied to the carbon nanotubes 4 by way of the metal substrate
1A. The electrons to be supplied are those electrons which
originated from the electrons emitted from the carbon nanotubes 4
and which routed back through the electron collector electrode and
load resistance to the electron emission electrode. When the
electron emission and the electron supply, as shown in FIG. 14, are
continuously repeated, the electrons circulate and do not
dissipate. The kinetic energy of electrons is released to the
outside as the thermal energy when the electrons pass through the
load resistance, while at the same time the thermal energy
corresponding to the dissipated energy is supplied from the heat
source H, thus the energy conservation law is satisfied.
[0237] As the heat source, any waste heat including the thermal
energy produced from the engine of a motor vehicle and the thermal
energy produced when the garbage is burnt in an incinerator can be
effectively used. A technology that makes use of such waste heat
energy is the technology required to sustain the earth
environment.
Third Embodiment
[0238] The third embodiment in accordance with the present
invention is described in greater details herein below. The same
reference numerals are used for the same elements as those of the
first and second embodiments, and only the different elements are
described in details.
[0239] FIG. 15 shows a schematic block diagram illustrating a
carbon nanotube manufacturing apparatus in accordance with the
third embodiment of the present invention.
[0240] As shown in FIG. 15, the carbon nanotube manufacturing
apparatus 3000 includes a catalyst film forming apparatus 200 for
forming a catalyst film 3 on the surface of a silicon substrate 5
which is a silicon layer, to thereby form a growth substrate 55, an
aligned growth apparatus 300 for using the catalytic function of
the catalyst film 3 to cause the aligned growth of a plurality of
carbon nanotubes 4 . . . on the growth substrate 55 (silicon
substrate 5), a metal film vapor depositing apparatus 700 for vapor
depositing a metal film 111a on the side having the tips 4b of the
alignedly grown carbon nanotubes 4 . . . , a metal layer plating
apparatus 800 for plating further a metal layer 111b on the vapor
deposited metal film 111a, and a substrate separator apparatus 600
for separating the carbon nanotubes 4 . . . from the silicon
substrate 5.
[0241] The carbon nanotube manufacturing method using the carbon
nanotube manufacturing apparatus 3000 is described in greater
details herein below.
[0242] FIG. 16 shows a flow diagram illustrating the manufacturing
steps of the carbon nanotube manufacturing method in accordance
with the third embodiment of the present invention, and FIG. 17
shows a series of schematic diagrams corresponding to the
manufacturing process steps shown in FIG. 16.
[0243] As shown in FIG. 16, the carbon nanotube manufacturing
method in accordance with the third embodiment mainly includes
following six processes (six steps): a growth substrate preparation
step (S301) for preparing a silicon substrate 5, a catalyst film
formation step (S302) for forming a catalyst film 3 on the surface
of the silicon substrate 5, an aligned growth step (S303) for
causing the aligned growth of the carbon nanotubes 4 . . . on the
surface of the silicon substrate 5 while the carbon nanotubes 4 . .
. are trapping as the nuclei the catalyst particles which form the
formed catalyst film 3 as nuclei, a metal film vapor deposition
step (S304) for vapor depositing a metal film 111a on the side
having the tips 4b of the alignedly grown carbon nanotubes 4 . . .
, a metal layer plating step (S305) as a metal layer formation step
for plating a metal layer 111b on the vapor deposited metal film
111a, a substrate separation step (S306) for separating the carbon
nanotubes 4 . . . from the silicon substrate 5.
[0244] The growth substrate preparation step in the step S301 is a
step for preparing the silicon substrate 5 on which the carbon
nanotubes 4 . . . are formed, as shown in FIG. 17 (a).
[0245] The silicon substrate 5 may be a plate-like member made of
for example an n-type silicon.
[0246] The catalyst film formation step in step S302 is a step for
forming the catalyst film 3 on the surface of the silicon substrate
5 by the catalyst film forming apparatus 200, to thereby form the
growth substrate 55, as shown in FIG. 17 (b).
[0247] The aligned growth step in step S303 is a step for causing
the aligned growth of the carbon nanotubes 4 . . . on the surface
of the silicon substrate 5 of the growth substrate 55 by the
aligned growth apparatus 300, as shown in FIG. 17 (c).
[0248] The carbon nanotubes 4 . . . are alignedly grown and formed
by the aligned growth apparatus 300 shown in FIG. 2.
[0249] The aligned growth method of the carbon nanotubes 4 . . . in
the aligned growth step is generally similar to the step S104 of
the first embodiment, and the aligned growth apparatus 300 also is
identical, so that the detailed description is omitted here.
[0250] The metal film vapor deposition step in the step S304 is a
step for vapor depositing a metal film 111a on the side having the
tips 4b of the carbon nanotubes 4 . . . by using the metal film
vapor deposition apparatus 700, as shown in FIG. 17 (d). The metal
film vapor deposition apparatus 700 is an apparatus similar to the
catalyst film forming apparatus 200, and is for example one of the
vacuum vapor deposition apparatus, molecular beam epitaxy (MBE)
apparatus, ion plating apparatus, ion beam epitaxy apparatus,
sputtering apparatus, and plating apparatus.
[0251] The metal film vapor deposition apparatus 700 vapor deposits
a metal layer 111a made of for instance aluminum, nickel, or copper
to the thickness of a few nanometers to several hundreds nanometers
on the side having the tips 4b of the carbon nanotubes 4 . . .
.
[0252] The metal layer plating step in the step S305 is a step for
plating a metal layer 111b on the deposited metal film 111a by
using the metal layer plating apparatus 800, as shown in FIG. 17
(e). A common plating apparatus can be used for the metal layer
plating apparatus 800.
[0253] The silicon substrate 5 (the silicon substrate 5 in which
the metal film 111a is vapor deposited on the carbon nanotubes 4 .
. . formed on the surface of the silicon substrate 5) is dipped in
a copper plating solution contained in a plating bath of the metal
layer plating apparatus 800 (a solution containing 50 grams of
copper sulfate (CuSO.sub.4), 12.5 cc of sulfuric acid
(H.sub.2SO.sub.4), 225 cc of water (H.sub.2O), a trace of sodium
chloride (NaCl)), and a metal layer 111b (for example, a metal
layer formed from copper) having a thickness of a few nanometers to
several hundreds nanometers is plated on the surface of the metal
film 111a. In the present embodiment, the metal film 111a of the
silicon substrate 5 dipped in a copper plating solution at the
temperature of 40 to 50 degrees centigrade was subjected to plating
for one hour with the electric current density of 0.05 to 0.1
ampere to form the metal layer 111b.
[0254] The plating by the metal layer plating apparatus 800 is not
limited to copper plating, and it may include plating of such
metals as gold, indium, silver, nickel alloys (pure Ni, Ni--Fe,
Ni--Cr, and Ni--Cu), cobalt alloys (pure Co, Co--Ni, Co--Cr, and
Co--Fe), iron alloys (pure Fe, Fe--Cr, and Fe--Ta), and aluminium
alloys (pure Al, Al--Cu, Al--Ti, and Al--Nd).
[0255] The substrate separation step in the step S306 is a step for
separating the carbon nanotubes 4 . . . from the silicon substrate
5 by the substrate separating apparatus 600 to thereby dispose the
carbon nanotubes 4 . . . on a metal substrate (the metal film 111a,
the metal layer 111b), as shown in FIG. 17 (f).
[0256] The methods of separating carbon nanotubes 4 . . . from the
silicon substrate 5 include, in addition to the method described in
the second embodiment above, a method for separation in which a
large current is applied through the silicon substrate 5 to heat
the silicon substrate 5 so as to facilitate the peeling off and
separation of the carbon nanotubes 4 . . . , a method for
separation in which ultrasound waves are applied to the silicon
substrate 5 to facilitate the peeling off and separation of the
carbon nanotubes 4 . . . , and so on.
[0257] The carbon nanotubes 4 . . . implanted in a metal substrate
formed from the metal film 111a and the metal layer 111b have for
example a diameter of a few nanometers to over ten nanometers and a
length of 1 micrometer to several tens micrometers, and they are
formed in the order of a million to ten billions per each square
millimeter (mm.sup.2).
[0258] With such apparatus and method, the carbon nanotubes 4 . . .
can be suitably manufactured similarly to the preceding first and
second embodiments. The well aligned carbon nanotubes 4 . . . can
be orderly grown on a metal substrate.
[0259] The carbon nanotubes 4 . . . on the silicon substrate 5
having metal layer 111b formed thereon by the metal layer plating
step shown in FIG. 17 (e) may further be grown thereafter by the
aligned growth apparatus 300.
Fourth Embodiment
[0260] The fourth embodiment in accordance with the present
invention is described in greater details herein below. The same
reference numerals are used for the same elements as those of the
first, second and third embodiments, and only the different
elements are described in details.
[0261] FIG. 18 and FIG. 19 show schematic diagrams illustrating the
carbon nanotube manufacturing method in accordance with the fourth
embodiment of the present invention.
[0262] As shown FIG. 18 and FIG. 19, the carbon nanotube
manufacturing method in accordance with the fourth embodiment of
the present invention is a method for manufacturing carbon
nanotubes based on the carbon nanotubes substrate (CNT substrate)
having the carbon nanotubes 4 . . . implanted in a metal substrate
comprising a metal film 111a and a metal layer 111b shown in FIG.
17 (f), which substrate was produced in accordance with the third
embodiment of the present invention, so that more CNT substrates
can be produced.
[0263] FIG. 18 (a) shows a CNT substrate produced in accordance
with the third embodiment of the present invention.
[0264] The CNT substrate is mounted on a predetermined place in the
aligned growth apparatus 300 (on the anode substrate 23 of the
electric field generator 20) to cause well aligned carbon nanotubes
4 . . . to be further grown from the tips of the carbon nanotubes 4
. . . disposed on the CNT substrate in the second step of aligned
growth (see FIG. 18 (b)).
[0265] Then, in a manner similar to the metal film vapor deposition
step (see FIG. 12 (d)) in accordance with the second embodiment, a
metal layer 111b is vapor deposited, by a metal layer vapor
depositing apparatus, for example, around the sides of the carbon
nanotube 4 . . . and on the surface of the metal film 111a in the
second step of metal layer formation (see FIG. 18 (c)).
[0266] Thereafter, well aligned carbon nanotubes 4 . . . are
further grown by the aligned growth apparatus 300 (see FIG. 18
(d)), and a metal layer 111b is vapor deposited by the metal layer
vapor deposition apparatus around the sides of the carbon nanotubes
4 . . . and on the surface of the metal layer 111b (see FIG. 18
(e)).
[0267] As can be appreciated from the foregoing description, the
iterative repetition of the aligned growth of the carbon nanotubes
4 . . . and the vapor deposition of metal layer 111b allows the
carbon nanotubes 4 . . . to be alignedly grown much longer, while
forming a CNT substrate like product covered by a thick metal layer
111b, as shown in FIG. 19 (f).
[0268] Next, the thick metal layer 111b of the CNT substrate-like
product shown in FIG. 19 (f) is sliced by a cutting device having
such as a diamond cutter at a predetermined thickness, in the
direction perpendicular to the direction of the aligned growth of
the carbon nanotubes 4 . . . (see FIG. 19 (g)).
[0269] Then, the cut surface side of the metal layer 111b of shown
in FIG. 19 (g) is removed to a predetermined depth by for example a
metal layer removing apparatus. The metal layer removing apparatus
may be an apparatus for dissolving the metal layer 111b, which
apparatus dissolves the metal 111b with a metal layer removing
solution (for instance, hydrochloric acid, nitric acid, sulfuric
acid) stored in the metal layer removing apparatus.
[0270] By dissolving and removing a predetermined thickness of the
metal layer 111b, the carbon nanotubes 4 . . . are exposed by a
predetermined length from the metal layer 111b (see FIG. 19
(h)).
[0271] In this manner, a CNT substrate as shown in FIG. 19 (h) can
be formed, which substrate comprises a metal layer 111b and carbon
nanotube 4 . . . , with the carbon nanotubes 4 . . . protruding
from the metal layer 111b by a predetermined length.
[0272] The carbon nanotubes 4 . . . disposed on a metal substrate
formed from the metal layer 111b have for example a diameter of a
few nanometers to over ten nanometers and a length of 1 micrometer
to several tens micrometers, and they are formed in the order of a
million to ten billions per each square millimeter (mm.sup.2).
[0273] With this method, the carbon nanotubes 4 can be suitably
formed similarly to the first, second and third embodiments. In
addition, well aligned carbon nanotubes 4 . . . can be orderly
disposed on the metal substrate.
[0274] More specifically, by starting from a CNT substrate having
carbon nanotubes 4 . . . disposed on a metal substrate (the metal
film 111a, the metal layer 111b), the iterative repetition of
aligned growth of the carbon nanotubes 4 . . . and the vapor
deposition (lamination) of the metal layer 111b allows the
formation of a number of CNT substrates (a CNT substrate comprising
a metal layer 111b and carbon nanotubes 4).
[0275] This method does not need any expensive silicon substrate in
the manufacturing process, allowing the manufacturing cost to be
reduced.
[0276] In addition, this method does not need a process of forming
a catalyst film by using a catalyst film forming apparatus such as
a sputtering apparatus, allowing also the manufacturing cost to be
reduced.
[0277] In particular, by the application of CNT substrate-like
product as shown in FIG. 19 (f), a copper wire containing extremely
long carbon nanotubes 4 . . . (when the metal layer 111b is made of
copper) can be manufactured. The well aligned carbon nanotubes 4 .
. . are orderly disposed along the direction of electric power
transmission of the copper wire (conducting wire), making the
conducting wire super low resistant, thus providing a conducting
wire which allows the electric power transmission loss to be
significantly decreased.
[0278] At the time when the metal layer removing apparatus
dissolves and removes a predetermined thickness from the cut
surface side of the metal layer 111b of the slice shown FIG. 19
(g), the metal layer 111b can be dissolved not only in one single
cut surface side as shown in FIG. 19 (h), but also can be dissolved
in both sides of the metal layer 111b, as shown in FIG. 19 (i), so
as to form a CNT substrate having a structure in which the carbon
nanotubes 4 . . . extend through the metal layer 111b and are
exposed from both sides of the metal layer 111b.
[0279] By using the carbon nanotube manufacturing apparatus and
manufacturing method in accordance with the present invention well
aligned carbon nanotubes 4 . . . can be produced at a higher
productivity. The carbon nanotube manufacturing apparatus as
described above, which uses methanol for the raw material of carbon
nanotube 4 . . . though, facilitates easier maintenance and control
of the apparatus in preventing the explosion and fire of
methanol.
[0280] Although, in the description of the preferred embodiments
above, methanol has been cited for the organic substance as the raw
material by way of example, the present invention should not be
considered to be limited thereto, and the usable organic substances
may be any substance that contains carbons (C), such as for example
ethanol, 1-butanol, 1-octanol, and the like.
[0281] Depending on the type of organic substances being used, a
variety of types and shapes of carbon nanotubes can be
manufactured.
[0282] It should be noted here that any other details and
structures can be appropriately modified.
[0283] For instance, when the carbon nanotubes are being grown, the
growth substrate may be rotated in order to eliminate the
non-uniformity due to the growth location.
[0284] For instance, instead of replacing the gas in the apparatus
with an inert gas (argon), the gas can be replaced with nitrogen
gas.
INDUSTRIAL APPLICABILITY
[0285] The carbon nanotube manufacturing method using the carbon
nanotube manufacturing apparatus in accordance with the present
invention allows the manufacture of well aligned carbon nanotubes
by growing carbon nanotubes in a gas phase in the direction of the
applied electric field by the effect of electric field.
Consequently, the present invention can manufacture well aligned
carbon nanotubes, with easier maintenance and control than the
conventional method in which carbon nanotubes are formed by dipping
a silicon substrate in the alcohol solution.
[0286] With a plurality of well aligned carbon nanotubes, the
electric field can be applied in the longitudinal direction of
almost all of the carbon nanotubes, so that the electric field is
concentrated at the tips of the carbon nanotubes and electrons are
locally concentrated thereto. The electrons can be emitted from the
tips of the carbon nanotubes at a high efficiency, allowing the
emission efficiency to be increased.
[0287] Consequently, the product can be used as the electron
emission electrode which emits electrons from the carbon nanotubes,
and by recycling the electrons emitted from the electron emission
electrode, the product can be applied to an electric power
generator for generating electric current.
* * * * *