US20100047152A1 - Growth of carbon nanotubes using metal-free nanoparticles - Google Patents
Growth of carbon nanotubes using metal-free nanoparticles Download PDFInfo
- Publication number
- US20100047152A1 US20100047152A1 US12/441,132 US44113207A US2010047152A1 US 20100047152 A1 US20100047152 A1 US 20100047152A1 US 44113207 A US44113207 A US 44113207A US 2010047152 A1 US2010047152 A1 US 2010047152A1
- Authority
- US
- United States
- Prior art keywords
- metal
- nanoparticle
- substrate
- carbon
- nanoparticles
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 title claims abstract description 172
- 239000002105 nanoparticle Substances 0.000 title claims abstract description 117
- 239000002041 carbon nanotube Substances 0.000 title claims abstract description 103
- 229910021393 carbon nanotube Inorganic materials 0.000 title claims abstract description 102
- 239000003054 catalyst Substances 0.000 claims abstract description 66
- 238000000034 method Methods 0.000 claims abstract description 50
- 229910052799 carbon Inorganic materials 0.000 claims abstract description 47
- 239000000758 substrate Substances 0.000 claims description 70
- 238000005229 chemical vapour deposition Methods 0.000 claims description 32
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims description 24
- 239000000463 material Substances 0.000 claims description 19
- 239000004065 semiconductor Substances 0.000 claims description 15
- 239000005543 nano-size silicon particle Substances 0.000 claims description 14
- HSFWRNGVRCDJHI-UHFFFAOYSA-N Acetylene Chemical compound C#C HSFWRNGVRCDJHI-UHFFFAOYSA-N 0.000 claims description 12
- 239000000377 silicon dioxide Substances 0.000 claims description 11
- 238000000137 annealing Methods 0.000 claims description 10
- 229910052681 coesite Inorganic materials 0.000 claims description 10
- 229910052906 cristobalite Inorganic materials 0.000 claims description 10
- 229910052682 stishovite Inorganic materials 0.000 claims description 10
- 229910052905 tridymite Inorganic materials 0.000 claims description 10
- 230000004888 barrier function Effects 0.000 claims description 9
- 239000004215 Carbon black (E152) Substances 0.000 claims description 6
- YBMRDBCBODYGJE-UHFFFAOYSA-N germanium dioxide Chemical compound O=[Ge]=O YBMRDBCBODYGJE-UHFFFAOYSA-N 0.000 claims description 6
- 229930195733 hydrocarbon Natural products 0.000 claims description 6
- 150000002430 hydrocarbons Chemical class 0.000 claims description 6
- 230000003993 interaction Effects 0.000 claims description 4
- 125000004432 carbon atom Chemical group C* 0.000 claims description 3
- 229910052710 silicon Inorganic materials 0.000 abstract description 15
- 229910052751 metal Inorganic materials 0.000 abstract description 11
- 239000002184 metal Substances 0.000 abstract description 11
- 229910052732 germanium Inorganic materials 0.000 abstract description 10
- 239000012535 impurity Substances 0.000 abstract description 9
- 239000007789 gas Substances 0.000 description 37
- 230000015572 biosynthetic process Effects 0.000 description 13
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 description 9
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 8
- 239000010703 silicon Substances 0.000 description 8
- 239000011148 porous material Substances 0.000 description 7
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 6
- 229910052755 nonmetal Inorganic materials 0.000 description 6
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 5
- 229910052739 hydrogen Inorganic materials 0.000 description 5
- 239000001257 hydrogen Substances 0.000 description 5
- 230000007246 mechanism Effects 0.000 description 5
- 229910052581 Si3N4 Inorganic materials 0.000 description 4
- 230000008901 benefit Effects 0.000 description 4
- 238000000151 deposition Methods 0.000 description 4
- 239000011261 inert gas Substances 0.000 description 4
- 238000004519 manufacturing process Methods 0.000 description 4
- 229910021420 polycrystalline silicon Inorganic materials 0.000 description 4
- 235000012239 silicon dioxide Nutrition 0.000 description 4
- 238000006243 chemical reaction Methods 0.000 description 3
- 230000001419 dependent effect Effects 0.000 description 3
- 230000008021 deposition Effects 0.000 description 3
- GNPVGFCGXDBREM-UHFFFAOYSA-N germanium atom Chemical compound [Ge] GNPVGFCGXDBREM-UHFFFAOYSA-N 0.000 description 3
- 239000002082 metal nanoparticle Substances 0.000 description 3
- 239000002071 nanotube Substances 0.000 description 3
- 229910052757 nitrogen Inorganic materials 0.000 description 3
- 238000000623 plasma-assisted chemical vapour deposition Methods 0.000 description 3
- 238000002203 pretreatment Methods 0.000 description 3
- 239000010453 quartz Substances 0.000 description 3
- 238000004626 scanning electron microscopy Methods 0.000 description 3
- HBMJWWWQQXIZIP-UHFFFAOYSA-N silicon carbide Chemical compound [Si+]#[C-] HBMJWWWQQXIZIP-UHFFFAOYSA-N 0.000 description 3
- 229910010271 silicon carbide Inorganic materials 0.000 description 3
- 239000000126 substance Substances 0.000 description 3
- 238000011282 treatment Methods 0.000 description 3
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 description 2
- JBRZTFJDHDCESZ-UHFFFAOYSA-N AsGa Chemical compound [As]#[Ga] JBRZTFJDHDCESZ-UHFFFAOYSA-N 0.000 description 2
- VGGSQFUCUMXWEO-UHFFFAOYSA-N Ethene Chemical compound C=C VGGSQFUCUMXWEO-UHFFFAOYSA-N 0.000 description 2
- 239000005977 Ethylene Substances 0.000 description 2
- 229910000577 Silicon-germanium Inorganic materials 0.000 description 2
- 229910021486 amorphous silicon dioxide Inorganic materials 0.000 description 2
- 238000000231 atomic layer deposition Methods 0.000 description 2
- 150000001722 carbon compounds Chemical class 0.000 description 2
- 238000005336 cracking Methods 0.000 description 2
- 125000002534 ethynyl group Chemical group [H]C#C* 0.000 description 2
- 238000011066 ex-situ storage Methods 0.000 description 2
- 238000002474 experimental method Methods 0.000 description 2
- 239000012634 fragment Substances 0.000 description 2
- 239000011521 glass Substances 0.000 description 2
- 238000010438 heat treatment Methods 0.000 description 2
- 230000006872 improvement Effects 0.000 description 2
- 238000011065 in-situ storage Methods 0.000 description 2
- 239000000203 mixture Substances 0.000 description 2
- 239000002245 particle Substances 0.000 description 2
- 238000000746 purification Methods 0.000 description 2
- 238000003786 synthesis reaction Methods 0.000 description 2
- 229910052715 tantalum Inorganic materials 0.000 description 2
- 238000002230 thermal chemical vapour deposition Methods 0.000 description 2
- 229910052721 tungsten Inorganic materials 0.000 description 2
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 1
- UGFAIRIUMAVXCW-UHFFFAOYSA-N Carbon monoxide Chemical compound [O+]#[C-] UGFAIRIUMAVXCW-UHFFFAOYSA-N 0.000 description 1
- 229910001218 Gallium arsenide Inorganic materials 0.000 description 1
- GPXJNWSHGFTCBW-UHFFFAOYSA-N Indium phosphide Chemical compound [In]#P GPXJNWSHGFTCBW-UHFFFAOYSA-N 0.000 description 1
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 description 1
- 229910003921 SiC(111) Inorganic materials 0.000 description 1
- LEVVHYCKPQWKOP-UHFFFAOYSA-N [Si].[Ge] Chemical compound [Si].[Ge] LEVVHYCKPQWKOP-UHFFFAOYSA-N 0.000 description 1
- 229910021529 ammonia Inorganic materials 0.000 description 1
- 229910003481 amorphous carbon Inorganic materials 0.000 description 1
- 238000013459 approach Methods 0.000 description 1
- 238000012769 bulk production Methods 0.000 description 1
- 229910002090 carbon oxide Inorganic materials 0.000 description 1
- 238000003421 catalytic decomposition reaction Methods 0.000 description 1
- 239000000919 ceramic Substances 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 238000003618 dip coating Methods 0.000 description 1
- 238000004090 dissolution Methods 0.000 description 1
- 238000010891 electric arc Methods 0.000 description 1
- 208000021302 gastroesophageal reflux disease Diseases 0.000 description 1
- 238000004050 hot filament vapor deposition Methods 0.000 description 1
- 239000003999 initiator Substances 0.000 description 1
- 230000000977 initiatory effect Effects 0.000 description 1
- 238000010849 ion bombardment Methods 0.000 description 1
- 238000005468 ion implantation Methods 0.000 description 1
- 238000000608 laser ablation Methods 0.000 description 1
- 239000007769 metal material Substances 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 229910003465 moissanite Inorganic materials 0.000 description 1
- 239000002159 nanocrystal Substances 0.000 description 1
- 229910017604 nitric acid Inorganic materials 0.000 description 1
- 230000003647 oxidation Effects 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- 230000001590 oxidative effect Effects 0.000 description 1
- 239000004033 plastic Substances 0.000 description 1
- 239000002243 precursor Substances 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- 230000008569 process Effects 0.000 description 1
- 238000012545 processing Methods 0.000 description 1
- 239000012495 reaction gas Substances 0.000 description 1
- 230000006798 recombination Effects 0.000 description 1
- 238000005215 recombination Methods 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 230000003252 repetitive effect Effects 0.000 description 1
- 229910052594 sapphire Inorganic materials 0.000 description 1
- 239000010980 sapphire Substances 0.000 description 1
- 239000011856 silicon-based particle Substances 0.000 description 1
- GUVRBAGPIYLISA-UHFFFAOYSA-N tantalum atom Chemical compound [Ta] GUVRBAGPIYLISA-UHFFFAOYSA-N 0.000 description 1
- WFKWXMTUELFFGS-UHFFFAOYSA-N tungsten Chemical compound [W] WFKWXMTUELFFGS-UHFFFAOYSA-N 0.000 description 1
- 239000010937 tungsten Substances 0.000 description 1
- 239000010457 zeolite Substances 0.000 description 1
Images
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B82—NANOTECHNOLOGY
- B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
- B82Y40/00—Manufacture or treatment of nanostructures
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B32/00—Carbon; Compounds thereof
- C01B32/15—Nano-sized carbon materials
- C01B32/158—Carbon nanotubes
- C01B32/16—Preparation
- C01B32/162—Preparation characterised by catalysts
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J21/00—Catalysts comprising the elements, oxides, or hydroxides of magnesium, boron, aluminium, carbon, silicon, titanium, zirconium, or hafnium
- B01J21/06—Silicon, titanium, zirconium or hafnium; Oxides or hydroxides thereof
- B01J21/08—Silica
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
- B01J23/14—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of germanium, tin or lead
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J27/00—Catalysts comprising the elements or compounds of halogens, sulfur, selenium, tellurium, phosphorus or nitrogen; Catalysts comprising carbon compounds
- B01J27/20—Carbon compounds
- B01J27/22—Carbides
- B01J27/224—Silicon carbide
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B82—NANOTECHNOLOGY
- B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
- B82Y30/00—Nanotechnology for materials or surface science, e.g. nanocomposites
Definitions
- the present invention relates to the growth of carbon nanotubes. More particularly, the present invention relates to the growth of carbon nanotubes using metal-free nanoparticles.
- Carbon nanotubes in general exhibit very good electronic and mechanical properties. Therefore, CNTs are expected to find a large diversity of industrial applications. One of these applications could be the use as both passive and active components in nano-electronic devices.
- the most commonly accepted growth mechanism for CNTs is based on catalytic decomposition of a carbon source on a surface of a metal nanoparticle which acts as catalyst in the CNT synthesis.
- the hydrocarbon source decomposes on front-exposed surfaces of the metal nanoparticle thereby releasing hydrogen and carbon, which dissolves in the nanoparticle.
- the dissolved carbon then diffuses through the metal nanoparticle and is precipitated to initiate formation of CNTs.
- One of the key issues in the growth mechanisms described in the prior art is the need for a metal catalyst particle to initiate the carbon nanotube growth.
- a disadvantage thereof is that the metal catalyst particles can lead to the presence of impurities in the grown CNTs. Before the CNTs can be used in many applications, these impurities have to be removed.
- a variety of chemical and thermal oxidative treatments are usually required to remove the unwanted metal impurities from the CNTs. For example, a multi-step purification procedure may be used which involves the use of nitric acid reflux and thermal oxidation.
- Catalyst-free growth of CNTs has been achieved previously by using laser ablation and arc discharge CNT growth.
- these methods require very high temperatures, i.e. temperatures of above 3000° C. Due to these high required temperatures, these methods are not suitable for in-situ CNT growth and consequently require an ex-situ approach.
- these methods may give low production yields compared to CVD methods that can be performed at relatively low temperatures (450-1100° C.), can be in-situ or ex-situ, and give mass production yields.
- catalyst-free CNT growth has been reported to occur on SiC(111) above 1500° C.
- the catalyst-free growth of CNTs is in this document achieved by repetitive annealing a carbon face of hexagonal silicon carbide in vacuum at predefined temperature ranges.
- the CNTs are produced without the use of a metal catalyst but these CNTs grow with their axis parallel to the surface, or in other words aligned to the substrate, and cannot be considered feasible for mass production of CNTs.
- carbon nanotips are grown on a silicon substrate without the use of a catalyst by using plasma-enhanced hot filament chemical vapor deposition using a mixture of methane, ammonia and hydrogen as reaction gas.
- the carbon nanotips formation is realized by first growing a carbon film on the silicon substrate during a time period of an hour. A combination of further growth of the carbon film and ion bombardment by applying a negative bias of 430 V to the silicon substrate produces glow discharge and makes growth of the carbon nanotips possible.
- a method according to embodiments of the invention may use Chemical Vapour Deposition.
- the present invention provides a method for forming at least one carbon nanotube.
- the method comprises:
- a method according to embodiments of the present invention leads to formation of carbon nanotubes which do not comprise metal impurities.
- the temperature of the substrate may be kept between 800° C. and 1000° C.
- providing at least one metal-free catalyst nanoparticle to the Chemical Vapor Deposition reactor may be performed by:
- the at least one carbon nanotube can be formed on a substrate.
- decomposing the carbon source gas may be performed by using a hot filament, by using a plasma, or by using a combination of a hot filament and a plasma.
- the hot filament may be a metallic filament such as a W filament or a Ta filament.
- the hot filament may have a temperature suitable for decomposing or cracking the carbon source gas.
- the filament may be kept at a temperature of 950° C.
- providing at least one metal-free catalyst nanoparticle to a Chemical Vapor Deposition reactor may be performed by providing at least one semiconductor comprising nanoparticle, e.g. a Si or Ge comprising nanoparticle.
- the at least one Si comprising nanoparticle may, for example, be a SiC, a SiO 2 or a pure silicon nanoparticle.
- the at least one Ge comprising nanoparticle may, for example, be a GeO 2 or a pure Ge nanoparticle.
- providing at least one metal-free catalyst nanoparticle on a substrate is performed by:
- metal-free catalyst material e.g. a semiconductor material catalyst material
- Annealing may be performed at temperatures of between 500° C. and 800° C.
- the at least one metal-free catalyst nanoparticle may have a diameter of between 0.4 nm and 100 nm or of between 0.4 nm and 50 nm.
- the method may furthermore comprise, before providing at least one metal-free catalyst nanoparticle on the substrate, providing a barrier layer on the substrate for preventing interaction, e.g. chemical interaction, of the at least one metal-free catalyst nanoparticle with the substrate.
- the method may furthermore comprise pre-treating the at least one metal-free catalyst nanoparticle before providing it to the Chemical Vapor Deposition reactor.
- a pre-treatment may be removal of a native oxide (e.g. SiO 2 in case of Si nanoparticles) by means of, for example a HF dip (e.g. a dip in 2% HF for 5 minutes).
- the carbon source gas may be a hydrocarbon gas having one (C1) up to three (C3) carbon atoms.
- the carbon source gas may, for example, be CH 4 , C 2 H 4 , C 2 H 2 or C 3 H 6 .
- the carbon source gas may be CO.
- the CVD reactor in which the method according to embodiments of the invention is performed may comprise an inert gas and hydrogen.
- the inert gas may, for example, be nitrogen.
- the flow of gasses in the CVD reactor may, for example, be 4 l/min N 2 , 2 l/min H 2 , 0.5 l/min C 2 H 2 or 0.1 l/min C 2 H 2 .
- the present invention provides a carbon nanotube grown from a metal-free catalyst nanoparticle. It is an advantage that these nanotubes are free from metal impurities.
- the present invention provides the use of a metal-free catalyst nanoparticle to grow a carbon nanotube. It is an advantage that these nanotubes are free from metal impurities.
- FIG. 1 illustrates a method for forming metal-free CNT onto Si particles according to embodiments of the present invention.
- FIG. 2 and FIG. 3 schematically illustrate a reactor which can be used for growing metal-free CNTs on a substrate according to embodiments of the present invention.
- FIG. 4 , FIG. 5 and FIG. 6 illustrate a Scanning Electron Microscopy picture after growth of CNTs onto Si nanoparticles according to embodiments of the present invention.
- the present invention provides a method for forming at least one carbon nanotube (CNT).
- the method comprises:
- the at least one carbon nanotube may be formed on a substrate.
- the at least one metal-free catalyst nanoparticle may be provided on a substrate and the substrate with the at least one metal-free catalyst on it may then be transferred to the CVD reactor for the growth of CNTs.
- the CVD method used for growing CNTs may be thermal CVD or Plasma enhanced CVD (PE-CVD).
- PE-CVD Plasma enhanced CVD
- the method according to embodiments of the invention can be applied for growing CNTs according to a “base growth” principle or a “tip growth” principle. Occurring of a particular kind of growth principle depends on interactions between the catalyst nanoparticle and the underlying substrate.
- base growth also referred to as “rooth growth” refers to a growth mechanism where the nanoparticles used to initiate the CNT growth stay located at the substrate during growth.
- tip growth also referred to as “top down growth” refers to a growth mechanism where the CNTs growth having the CNT situated at the surface during growth and the catalyst nanoparticle on top of the CNT.
- non-metal containing nanoparticles refers to nanoparticles comprising a material different from a metal and suitable to be used as a catalyst nanoparticle for initiating the growth of CNTs.
- any non-metal containing nanoparticles can be used.
- the nanoparticles may comprise a semiconductor material such as silicon or germanium.
- the nanoparticles may be silicon comprising nanoparticles and may, for example, comprise pure Si, SiO 2 or SiC or may be germanium comprising nanoparticles and may, for example, comprise pure Ge or GeO 2 .
- the nanoparticles may be pure Si nanoparticles or pure Ge nanoparticles. Whenever in the description of the present invention reference is made to catalyst nanoparticles it has to be understood that non-metal containing catalyst nanoparticles are meant.
- a method according to embodiments of the invention allows synthesis of CNTs which do not comprise metal impurities because the growth starts from suitable non-metal containing catalyst nanoparticles onto which the CNT growth according to embodiments of the invention can take place. Hence, no purification process is required after formation of the CNTs.
- a method according to embodiments of the invention is suitable to be used for massive CNT growth and can be used in high production yield applications.
- the size of the catalyst nanoparticles may have an impact on the final diameter of the CNTs formed or, in other words, may determine the final diameter of the CNTs.
- the catalyst nanoparticles suitable to be used for growing CNTs according to a method of embodiments of the present invention may have a diameter in the range of between 0.4 nm and 100 nm or between 0.4 nm and 50 nm.
- a substrate 10 is provided (see FIG. 1 ).
- the term “substrate” may include any underlying material or materials that may be used, or upon which CNTs may be grown.
- the term “substrate” may include a semiconductor substrate such as e.g. a doped or undoped silicon, gallium arsenide (GaAs), gallium arsenide phosphide (GaAsP), indium phosphide (InP), germanium (Ge), or silicon germanium (SiGe) substrate.
- GaAs gallium arsenide
- GaAsP gallium arsenide phosphide
- InP indium phosphide
- Ge germanium
- SiGe silicon germanium
- the “substrate” may include, for example, an insulating layer such as a SiO 2 or an Si 3 N 4 layer in addition to a semiconductor substrate portion.
- the term “substrate” also includes glass, plastic, ceramic, silicon-on-glass, silicon-on-sapphire substrates.
- the term “substrate” is thus used to define generally the elements for layers that underlie a layer or portions of interest, in particular for the present invention the CNTs to be grown.
- the substrate 10 may be a semicondcutor wafer, e.g. a Si wafer or a Ge wafer.
- a major surface of the substrate 10 should be inert with respect to CNT growth or should be such that it does not interact with the catalyst nanoparticles formed on it. Therefore, according to embodiments of the invention a barrier layer 11 may be provided onto the substrate before catalyst nanoparticles are formed on it (see further).
- a thin layer 12 of non-metal material is provided, e.g. deposited onto a major surface of the substrate 10 .
- This layer 12 may, for example, comprise seumiconductor material such as Si or Ge.
- this thin layer 12 may be a uniformly deposited thin layer, such as a poly-Si (polycrystalline Silicon), amorphous silicon or silicon dioxide layer deposited by commonly used deposition techniques such as, for example, CVD (Chemical Vapor Deposition).
- the thickness of the thin layer 12 may be less than 15 nm and may, for example, be between 0.4 nm and 5 nm.
- the thin layer 12 may also be a non-uniform sub-atomic layer deposited by e.g. ALD (Atomic Layer Deposition). Alternatively spin-on and dip coating techniques may be used to deposit a uniform thin layer 12 .
- ALD Atomic Layer Deposition
- spin-on and dip coating techniques may be used to deposit a uniform thin layer 12 .
- a barrier layer 11 can be deposited onto the substrate 10 before the deposition of the thin layer 12 (see FIG. 1 ).
- the barrier layer 11 may, for example, be used to prevent reaction of the material of the thin layer 12 , e.g. semiconductor layer such as Si or Ge layer, and/or formed nanoparticles with the substrate 10 underneath.
- the barrier layer 11 may, for example, be a Si 3 N 4 layer or any other suitable layer that prevents reaction of the material of the thin layer 12 with the substrate 10 .
- an annealing step may be performed to break up the thin layer 12 and to form nanoparticles 14 (see step 13 in FIG. 1 ).
- the formed nanoparticles 14 may have a diameter of between 0.4 nm and 100 nm and may, for example, have a diameter of between 0.4 nm and 50 nm.
- FIG. 1 illustrates the formation of the nanoparticles 14 .
- the thickness of the deposited thin layer 12 as well as the temperature and time of the annealing step may be controlled or well-chosen.
- the optimal temperature and time to create the nanoparticles 14 depends on the type and the thickness of the deposited thin layer 12 of metal-free material.
- the temperature for annealing may range between 500° C. and 800° C.
- the anneal step may be performed in a reactor. In the reactor, gases such as nitrogen and/or hydrogen can be used as ambient gases.
- nanoparticles 14 which may, for example, comprise pure semiconductor material, e.g. pure Si, may be formed in a thin dielectric layer, e.g. a SiO 2 layer, which is provided, e.g. deposited for example by CVD, onto the substrate 10 , for example onto a semiconductor wafer, e.g. Si wafer.
- a low energy Si ion implantation step may be performed on the SiO 2 layer followed by an annealing step to create Si nanocrystals.
- a dissolving treatment e.g. HF treatment (e.g. HF vapor or dilute solution), can then be applied to remove the SiO 2 such that Si nanoparticles 14 which are suitable for use as initiators of CNT growth are left on the substrate 10 .
- the substrate 10 onto which the nanoparticles 14 are formed or deposited may be formed of a porous material.
- suitable porous materials to be used with embodiments of the present invention may be zeolites and porous low-k materials (commonly used in semiconductor processing and commercially available).
- Using porous material or in other words using a substrate 10 having inner pores makes it possible to deposit the thin layer 12 not only on the major surface of the substrate 10 but also within these inner pores of the substrate 10 . This significantly increases the surface area onto which nanoparticles 14 can be formed. As a result the amount of CNTs which can be formed by the method according to embodiments of the invention may also significantly increase.
- a thin layer 12 of, for example, semiconductor material, e.g. Si, the layer being continuous or non continuous, may be deposited onto a major surface of the porous substrate 10 and on the surface of the inner pores of the porous substrate 10 .
- nanoparticles 14 may be formed on the major surface of the substrate 10 and in the inner pores of the substrate 10 . These nanoparticles 14 can then be used as catalysts to grow CNTs.
- bulk catalyst nanoparticles may be provided to grow CNTs.
- the bulk nanoparticles should be such that a carbon source gas is able to flow in between neighbouring nanoparticles such that, when the bulk catalyst nanoparticles are provided in a reactor, CNTs can be grown onto the catalyst nanoparticles (see further).
- the nanoparticles 14 e.g. semiconductor nanoparticles such as Si or Ge nanoparticles
- An example of such a pre-treatment may be removal of a native oxide (e.g. SiO 2 in case of Si nanoparticles) by means of, for example a HF dip (e.g. a dip in 2% HF for 5 minutes).
- the substrate 10 on which the nanoparticles 14 are formed, or according to alternative embodiments the bulk nanoparticles are transferred to a suitable reactor chamber of a reactor such as a Chemical Vapor Deposition (CVD) reactor to grow the CNTs 16 (see step 15 in FIG. 1 ).
- the CVD reactor can, for example, be a Plasma Enhanced CVD reactor or a Thermal CVD reactor.
- a carbon source gas is decomposed or cracked by heating it. Cracking the carbon source gas leads to formation of different carbon fragments such that these fragments can be recombined on the catalyst nanoparticles to form a CNT. Recombination thus takes place at a surface of the formed nanoparticles 14 , e.g. semiconductor comprising nanoparticles such as Si or Ge comprising nanoparticles.
- Heating the carbon source gas may, according to embodiments of the invention, be done by using a hot filament, by using a plasma or by using a combination of a hot filament and a plasma.
- this hot filament may be located in the reactor chamber such that cracked or decomposed carbon species do not recombine before they have reached the catalyst nanoparticles so as to grow CNTs (see further).
- the hot filament may be a metallic filament and can comprise W (Tungsten) or Ta (Tantalum) and is kept at high temperatures. The height of the temperature depends on the carbon source used and needs to be high enough to crack the carbon source. For example, the temperature of the hot filament may be 950° C. or higher.
- the temperature of the catalyst nanoparticles 14 and/or the substrate 10 on which the catalyst nanoparticles 14 are formed may be in the range of between 800° C. up to 1000° C.
- any suitable carbon source gas known by a person skilled in the art may be used.
- the carbon source gas may be a hydrocarbon source and may be a hydrocarbon gas having one (C1) up to three (C3) carbon atoms.
- suitable hydrocarbon gases to be used for CVD assisted CNT growth may be CH 4 , C 2 H 4 , C 2 H 2 or C 3 H 6 .
- alternative carbon sources such as carbon oxide (CO) can also be used as a carbon source gas.
- the amount of carbon source gas used in the reactor chamber determines the growth, morphology and properties of CNTs formed.
- the amount of carbon gas and/or the amount of cracked carbon fragments in the reactor chamber should be sufficient, i.e. high enough, to achieve CNT growth but on the other hand should be low enough so as to avoid formation of amorphous carbon onto the catalyst nanoparticles as in that case no CNT growth will occur.
- the CVD reactor chamber may furthermore comprise an inert gas and hydrogen.
- the inert gas may, for example, be nitrogen.
- the total flow of gasses in the CVD reactor during the step of forming CNTs 16 may be around 4 l/min N 2 , 2 l/min H 2 and 0.01 up to 1 l/min carbon gas such as e.g. C 2 H 2 .
- a suitable gas flow can be 4 l/min N 2 , 2 l/min H 2 and 0.1 l/min carbon gas such as C 2 H 2 .
- FIG. 2 and FIG. 3 Examples of a simplified reactor which may be used to perform CNT growth according to embodiments of the present invention is schematically illustrated in FIG. 2 and FIG. 3 .
- the difference between FIG. 2 and FIG. 3 is the location of the hot filament 2 .
- the reactor comprises a quartz tube 6 in which the substrate 10 comprising the nanoparticles 14 , e.g. semiconductor comprising nanoparticles such as Si or Ge comprising nanoparticles, is placed.
- a furnace 3 is situated at the outside of the quartz tube 6 and is used to create an optimal reaction temperature within the quartz tube 6 . With optimal temperature is meant a temperature at which CNT growth can take place.
- a hot filament 2 is placed at the entrance or gas inlet 1 of the reactor such that the carbon source, e.g.
- the carbon source gas is cracked into fragments which may then recombine on the nanoparticles 14 to form CNTs 16 .
- the hot filament 2 may be located above the substrate 10 . In the latter case, more extensive growth of CNTs may be obtained because in that case the cracked carbon species do not have to travel a long way to reach the catalyst nanoparticles 14 , and thus have a lower chance, with respect to the case illustrated in FIG. 2 , of recombining before having assisted in CNT growth.
- a simple release process such as, for example, chemical dissolution of the substrate 10 can be done.
- a silicon wafer was provided as a substrate 10 to grow the CNTs 16 on.
- a Si 3 N 4 barrier layer 11 was deposited in a vacuum reactor.
- a thin layer 12 of 5 nm poly-Si was deposited. Without breaking the vacuum the sample was annealed in conditions such that the thin layer 12 broke into nanoparticles 14 .
- the anneal step to break up the poly-Si layer 12 into Si nanoparticles 14 was performed at 530° C. during a time period of 20 minutes.
- the obtained Si nanoparticles 14 had a diameter of approximately 5 nm.
- the substrate 10 with the nanoparticles 14 on was then placed in a standard HF solution (2% HF) for a couple of minutes (e.g. 5 minutes) at room temperature so as to remove a possibly present native oxide formed after the nanoparticles have been exposed to air.
- the substrate 10 comprising the Si nanoparticles 14 was placed in a CVD reactor at 900° C. for 5 min.
- the reactor gases were N 2 and H 2 at a ratio of 4 l/min N 2 to 4 l/min H 2 .
- the Si nanoparticles 14 were found to be suitable for growing CNTs 16 according to a method of embodiments of the present invention.
- the nanoparticles 14 being suitable is meant that they can act as a template or precursor for CNT formation, in other words, that they can be used to initiate CNT growth.
- C 2 H 2 gas was added to the reactor at a flow of 0.5 l/min.
- N 2 and H 2 were also present in the reactor chamber during CNT growth at a ratio of 4 l/min N 2 to 2 l/min H 2 .
- the substrate temperature was in the range of between 800° C. and 1000° C., for example 900° C.
- FIG. 4 illustrates a scanning electron microscopy (SEM) picture of CNTs grown onto Si catalyst nanoparticles. It can be seen from FIG. 4 that, in the experiment conducted, nanotubes are grown at a pm scale distance.
- the substrates 10 with nanoparticles 14 on were etched in HF (2%) for 1 min. at room temperature in order to remove a possibly present native oxide from the Si nanoparticles 14 .
- the samples were placed in the CVD reactor chamber with temperatures ranging between 600° C. and 9000° C., under reducing atmosphere in N 2 :H 2 (4:2 l/min.) for 5 minutes at atmospheric pressure.
- a W wire was used as a hot filament 2 and was located above the substrate 10 comprising the catalyst nanoparticles 14 .
- a flow of 0.1 l/min. of acetylene, ethylene or methane in addition to the other gases (N 2 :H 2 ) was flown over the hot filament 2 such that the Carbon source gas was cracked.
- the gas composition used for this experiment was N 2 :H 2 :C at a ratio 4:2:0.1 l/min.
- the Carbon source used was either one of acetylene, ethylene or methane.
- the CNTs 16 were grown for half an hour at atmospheric pressure.
- FIG. 5 and FIG. 6 illustrate SEM pictures after growth of CNTs onto the Si nanoparticles according to embodiments of the present example. Massive growth of CNTs 16 was observed, i.e. CNTs were grown much closer to each other when compared to FIG. 4 . A more intensive growth was observed in the area where the Si nanoparticles are closer to the hot filament 2 (see upper row of CNTs 16 in FIG. 5 ).
Landscapes
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Nanotechnology (AREA)
- Organic Chemistry (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Physics & Mathematics (AREA)
- Condensed Matter Physics & Semiconductors (AREA)
- General Physics & Mathematics (AREA)
- Crystallography & Structural Chemistry (AREA)
- Inorganic Chemistry (AREA)
- Composite Materials (AREA)
- Manufacturing & Machinery (AREA)
- Carbon And Carbon Compounds (AREA)
- Catalysts (AREA)
Abstract
Description
- The present invention relates to the growth of carbon nanotubes. More particularly, the present invention relates to the growth of carbon nanotubes using metal-free nanoparticles.
- Carbon nanotubes (CNTs) in general exhibit very good electronic and mechanical properties. Therefore, CNTs are expected to find a large diversity of industrial applications. One of these applications could be the use as both passive and active components in nano-electronic devices.
- The most commonly accepted growth mechanism for CNTs is based on catalytic decomposition of a carbon source on a surface of a metal nanoparticle which acts as catalyst in the CNT synthesis. According to this growth mechanism, the hydrocarbon source decomposes on front-exposed surfaces of the metal nanoparticle thereby releasing hydrogen and carbon, which dissolves in the nanoparticle. The dissolved carbon then diffuses through the metal nanoparticle and is precipitated to initiate formation of CNTs.
- One of the key issues in the growth mechanisms described in the prior art is the need for a metal catalyst particle to initiate the carbon nanotube growth. A disadvantage thereof is that the metal catalyst particles can lead to the presence of impurities in the grown CNTs. Before the CNTs can be used in many applications, these impurities have to be removed. A variety of chemical and thermal oxidative treatments are usually required to remove the unwanted metal impurities from the CNTs. For example, a multi-step purification procedure may be used which involves the use of nitric acid reflux and thermal oxidation.
- Catalyst-free growth of CNTs has been achieved previously by using laser ablation and arc discharge CNT growth. However, these methods require very high temperatures, i.e. temperatures of above 3000° C. Due to these high required temperatures, these methods are not suitable for in-situ CNT growth and consequently require an ex-situ approach. Furthermore, these methods may give low production yields compared to CVD methods that can be performed at relatively low temperatures (450-1100° C.), can be in-situ or ex-situ, and give mass production yields.
- In Nanoletters, 2002 Vol. 2, No. 10, 1043-1046 (Derycke et al.), catalyst-free CNT growth has been reported to occur on SiC(111) above 1500° C. The catalyst-free growth of CNTs is in this document achieved by repetitive annealing a carbon face of hexagonal silicon carbide in vacuum at predefined temperature ranges. The CNTs are produced without the use of a metal catalyst but these CNTs grow with their axis parallel to the surface, or in other words aligned to the substrate, and cannot be considered feasible for mass production of CNTs.
- In Applied Surface Science 245 (2005) 21-25 (Wang et al.) carbon nanotips are grown on a silicon substrate without the use of a catalyst by using plasma-enhanced hot filament chemical vapor deposition using a mixture of methane, ammonia and hydrogen as reaction gas. The carbon nanotips formation is realized by first growing a carbon film on the silicon substrate during a time period of an hour. A combination of further growth of the carbon film and ion bombardment by applying a negative bias of 430 V to the silicon substrate produces glow discharge and makes growth of the carbon nanotips possible.
- It is an object of embodiments of the present invention to provide a good method for growing carbon nanotubes on a substrate.
- The above objective is accomplished by a method according to the present invention.
- It is an advantage of a method according to embodiments of the invention that the carbon nanotubes grown by this method do substantially not comprise metal impurities.
- A method according to embodiments of the invention may use Chemical Vapour Deposition.
- The present invention provides a method for forming at least one carbon nanotube. The method comprises:
- providing at least one metal-free catalyst nanoparticle to a Chemical Vapor Deposition reactor,
- forming reactive carbon fragments by decomposing a carbon source gas in the Chemical Vapor Deposition reactor, and
- recombining the reactive carbon fragments on top of the at least one metal-free catalyst nanoparticle to grow the at least one carbon nanotube.
- A method according to embodiments of the present invention leads to formation of carbon nanotubes which do not comprise metal impurities.
- During decomposing the carbon source gas and growing the at least one carbon nanotube, the temperature of the substrate may be kept between 800° C. and 1000° C.
- According to embodiments of the invention, providing at least one metal-free catalyst nanoparticle to the Chemical Vapor Deposition reactor may be performed by:
- providing at least one metal-free catalyst nanoparticle on a substrate, and
- transferring the substrate with the at least one metal-free nanoparticle on it to the Chemical Vapor Deposition reactor.
- According to these embodiments, the at least one carbon nanotube can be formed on a substrate.
- According to embodiments of the invention, decomposing the carbon source gas may be performed by using a hot filament, by using a plasma, or by using a combination of a hot filament and a plasma.
- The hot filament may be a metallic filament such as a W filament or a Ta filament. The hot filament may have a temperature suitable for decomposing or cracking the carbon source gas. For example when a hot filament is used for decomposing the carbon source gas, the filament may be kept at a temperature of 950° C.
- According to embodiments of the invention, providing at least one metal-free catalyst nanoparticle to a Chemical Vapor Deposition reactor may be performed by providing at least one semiconductor comprising nanoparticle, e.g. a Si or Ge comprising nanoparticle.
- The at least one Si comprising nanoparticle may, for example, be a SiC, a SiO2 or a pure silicon nanoparticle.
- The at least one Ge comprising nanoparticle may, for example, be a GeO2 or a pure Ge nanoparticle.
- According to embodiments of the invention, providing at least one metal-free catalyst nanoparticle on a substrate is performed by:
- providing a thin layer of metal-free catalyst material, e.g. a semiconductor material catalyst material, onto the substrate, and
- annealing the thin layer of metal-free material so as to break it up and form the at least one metal-free catalyst nanoparticle.
- Annealing may be performed at temperatures of between 500° C. and 800° C.
- According to embodiments of the invention, the at least one metal-free catalyst nanoparticle may have a diameter of between 0.4 nm and 100 nm or of between 0.4 nm and 50 nm.
- According to embodiments of the invention, the method may furthermore comprise, before providing at least one metal-free catalyst nanoparticle on the substrate, providing a barrier layer on the substrate for preventing interaction, e.g. chemical interaction, of the at least one metal-free catalyst nanoparticle with the substrate.
- According to further embodiments of the invention, the method may furthermore comprise pre-treating the at least one metal-free catalyst nanoparticle before providing it to the Chemical Vapor Deposition reactor. An example of such a pre-treatment may be removal of a native oxide (e.g. SiO2 in case of Si nanoparticles) by means of, for example a HF dip (e.g. a dip in 2% HF for 5 minutes).
- According to embodiments of the invention, the carbon source gas may be a hydrocarbon gas having one (C1) up to three (C3) carbon atoms. The carbon source gas may, for example, be CH4, C2H4, C2H2 or C3H6.
- According to other embodiments of the invention, the carbon source gas may be CO.
- The CVD reactor in which the method according to embodiments of the invention is performed may comprise an inert gas and hydrogen. The inert gas may, for example, be nitrogen.
- The flow of gasses in the CVD reactor may, for example, be 4 l/min N2, 2 l/min H2, 0.5 l/min C2H2 or 0.1 l/min C2H2.
- In a further aspect, the present invention provides a carbon nanotube grown from a metal-free catalyst nanoparticle. It is an advantage that these nanotubes are free from metal impurities.
- In yet a further aspect, the present invention provides the use of a metal-free catalyst nanoparticle to grow a carbon nanotube. It is an advantage that these nanotubes are free from metal impurities.
- Particular and preferred aspects of the invention are set out in the accompanying independent and dependent claims. Features from the dependent claims may be combined with features of the independent claims and with features of other dependent claims as appropriate and not merely as explicitly set out in the claims.
- Although there has been constant improvement, change and evolution of devices in this field, the present concepts are believed to represent substantial new and novel improvements, including departures from prior practices, resulting in the provision of more efficient, stable and reliable devices of this nature.
- The above and other characteristics, features and advantages of the present invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, which illustrate, by way of example, the principles of the invention. This description is given for the sake of example only, without limiting the scope of the invention. The reference figures quoted below refer to the attached drawings.
- All drawings are intended to illustrate some aspects and embodiments of the present invention. Not all alternatives and options are shown and therefore the invention is not limited to the content of the given drawings. Like numerals are employed to reference like parts in the different figures.
-
FIG. 1 illustrates a method for forming metal-free CNT onto Si particles according to embodiments of the present invention. -
FIG. 2 andFIG. 3 schematically illustrate a reactor which can be used for growing metal-free CNTs on a substrate according to embodiments of the present invention. -
FIG. 4 ,FIG. 5 andFIG. 6 illustrate a Scanning Electron Microscopy picture after growth of CNTs onto Si nanoparticles according to embodiments of the present invention. - In the different figures, the same reference signs refer to the same or analogous elements.
- The present invention will be described with respect to particular embodiments and with reference to certain drawings but the invention is not limited thereto but only by the claims. The drawings described are only schematic and are non-limiting. In the drawings, the size of some of the elements may be exaggerated and not drawn on scale for illustrative purposes. The dimensions and the relative dimensions do not correspond to actual reductions to practice of the invention.
- It is to be noticed that the term “comprising”, used in the claims, should not be interpreted as being restricted to the means listed thereafter; it does not exclude other elements or steps. It is thus to be interpreted as specifying the presence of the stated features, integers, steps or components as referred to, but does not preclude the presence or addition of one or more other features, integers, steps or components, or groups thereof. Thus, the scope of the expression “a device comprising means A and B” should not be limited to devices consisting only of components A and B. It means that with respect to the present invention, the only relevant components of the device are A and B.
- Reference throughout this specification to “one embodiment” or “an embodiment” means that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, appearances of the phrases “in one embodiment” or “in an embodiment” in various places throughout this specification are not necessarily all referring to the same embodiment, but may. Furthermore, the particular features, structures or characteristics may be combined in any suitable manner, as would be apparent to one of ordinary skill in the art from this disclosure, in one or more embodiments.
- Similarly it should be appreciated that in the description of exemplary embodiments of the invention, various features of the invention are sometimes grouped together in a single embodiment, figure, or description thereof for the purpose of streamlining the disclosure and aiding in the understanding of one or more of the various inventive aspects. This method of disclosure, however, is not to be interpreted as reflecting an intention that the claimed invention requires more features than are expressly recited in each claim. Rather, as the following claims reflect, inventive aspects lie in less than all features of a single foregoing disclosed embodiment. Thus, the claims following the detailed description are hereby expressly incorporated into this detailed description, with each claim standing on its own as a separate embodiment of this invention.
- Furthermore, while some embodiments described herein include some but not other features included in other embodiments, combinations of features of different embodiments are meant to be within the scope of the invention, and form different embodiments, as would be understood by those in the art. For example, in the following claims, any of the claimed embodiments can be used in any combination.
- In the description provided herein, numerous specific details are set forth. However, it is understood that embodiments of the invention may be practiced without these specific details. In other instances, well-known methods, structures and techniques have not been shown in detail in order not to obscure an understanding of this description.
- The invention will now be described by a detailed description of several embodiments of the invention. It is clear that other embodiments of the invention can be configured according to the knowledge of persons skilled in the art without departing from the true spirit or technical teaching of the invention, the invention being limited only by the terms of the appended claims.
- The present invention provides a method for forming at least one carbon nanotube (CNT). The method comprises:
- providing at least one metal-free catalyst nanoparticle to a Chemical Vapor Deposition (CVD) reactor,
- forming reactive carbon fragments by decomposing a carbon source gas in the Chemical Vapor Deposition reactor, and
- recombining the reactive carbon fragments on top of the at least one metal-free catalyst nanoparticle to grow the at least one carbon nanotube.
- According to embodiments of the invention, the at least one carbon nanotube may be formed on a substrate. According to these embodiments the at least one metal-free catalyst nanoparticle may be provided on a substrate and the substrate with the at least one metal-free catalyst on it may then be transferred to the CVD reactor for the growth of CNTs.
- The CVD method used for growing CNTs may be thermal CVD or Plasma enhanced CVD (PE-CVD).
- The method according to embodiments of the invention can be applied for growing CNTs according to a “base growth” principle or a “tip growth” principle. Occurring of a particular kind of growth principle depends on interactions between the catalyst nanoparticle and the underlying substrate. The term “base growth”, also referred to as “rooth growth” refers to a growth mechanism where the nanoparticles used to initiate the CNT growth stay located at the substrate during growth. The term “tip growth”, also referred to as “top down growth” refers to a growth mechanism where the CNTs growth having the CNT situated at the surface during growth and the catalyst nanoparticle on top of the CNT.
- Furthermore, the term “non-metal containing” nanoparticles refers to nanoparticles comprising a material different from a metal and suitable to be used as a catalyst nanoparticle for initiating the growth of CNTs. According to embodiments of the invention, any non-metal containing nanoparticles can be used. According to embodiments of the invention, the nanoparticles may comprise a semiconductor material such as silicon or germanium. For example, the nanoparticles may be silicon comprising nanoparticles and may, for example, comprise pure Si, SiO2 or SiC or may be germanium comprising nanoparticles and may, for example, comprise pure Ge or GeO2. According to specific embodiments of the invention, the nanoparticles may be pure Si nanoparticles or pure Ge nanoparticles. Whenever in the description of the present invention reference is made to catalyst nanoparticles it has to be understood that non-metal containing catalyst nanoparticles are meant.
- A method according to embodiments of the invention allows synthesis of CNTs which do not comprise metal impurities because the growth starts from suitable non-metal containing catalyst nanoparticles onto which the CNT growth according to embodiments of the invention can take place. Hence, no purification process is required after formation of the CNTs.
- Furthermore, a method according to embodiments of the invention is suitable to be used for massive CNT growth and can be used in high production yield applications.
- In general, the size of the catalyst nanoparticles may have an impact on the final diameter of the CNTs formed or, in other words, may determine the final diameter of the CNTs. The catalyst nanoparticles suitable to be used for growing CNTs according to a method of embodiments of the present invention may have a diameter in the range of between 0.4 nm and 100 nm or between 0.4 nm and 50 nm.
- Hereinafter, a method for growing CNTs will be described by means of
FIG. 1 . It has to be understood that the sequence of steps described hereinafter is not intended to limit the invention in any way. - In a first step, a
substrate 10 is provided (seeFIG. 1 ). In embodiments of the present invention, the term “substrate” may include any underlying material or materials that may be used, or upon which CNTs may be grown. According to embodiments, the term “substrate” may include a semiconductor substrate such as e.g. a doped or undoped silicon, gallium arsenide (GaAs), gallium arsenide phosphide (GaAsP), indium phosphide (InP), germanium (Ge), or silicon germanium (SiGe) substrate. The “substrate” may include, for example, an insulating layer such as a SiO2 or an Si3N4 layer in addition to a semiconductor substrate portion. Thus the term “substrate” also includes glass, plastic, ceramic, silicon-on-glass, silicon-on-sapphire substrates. The term “substrate” is thus used to define generally the elements for layers that underlie a layer or portions of interest, in particular for the present invention the CNTs to be grown. According to a specific embodiment of the present invention, thesubstrate 10 may be a semicondcutor wafer, e.g. a Si wafer or a Ge wafer. According to embodiments of the invention, a major surface of thesubstrate 10 should be inert with respect to CNT growth or should be such that it does not interact with the catalyst nanoparticles formed on it. Therefore, according to embodiments of the invention abarrier layer 11 may be provided onto the substrate before catalyst nanoparticles are formed on it (see further). - A
thin layer 12 of non-metal material, also referred to as metal-free material, is provided, e.g. deposited onto a major surface of thesubstrate 10. Thislayer 12 may, for example, comprise seumiconductor material such as Si or Ge. In case of, for example, Si comprising material, thisthin layer 12 may be a uniformly deposited thin layer, such as a poly-Si (polycrystalline Silicon), amorphous silicon or silicon dioxide layer deposited by commonly used deposition techniques such as, for example, CVD (Chemical Vapor Deposition). The thickness of thethin layer 12 may be less than 15 nm and may, for example, be between 0.4 nm and 5 nm. According to embodiments of the invention, thethin layer 12 may also be a non-uniform sub-atomic layer deposited by e.g. ALD (Atomic Layer Deposition). Alternatively spin-on and dip coating techniques may be used to deposit a uniformthin layer 12. - If needed, a
barrier layer 11 can be deposited onto thesubstrate 10 before the deposition of the thin layer 12 (seeFIG. 1 ). Thebarrier layer 11 may, for example, be used to prevent reaction of the material of thethin layer 12, e.g. semiconductor layer such as Si or Ge layer, and/or formed nanoparticles with thesubstrate 10 underneath. Thebarrier layer 11 may, for example, be a Si3N4 layer or any other suitable layer that prevents reaction of the material of thethin layer 12 with thesubstrate 10. - After deposition of the
thin layer 12, an annealing step may be performed to break up thethin layer 12 and to form nanoparticles 14 (seestep 13 inFIG. 1 ). The formednanoparticles 14 may have a diameter of between 0.4 nm and 100 nm and may, for example, have a diameter of between 0.4 nm and 50 nm.FIG. 1 illustrates the formation of thenanoparticles 14. To control the size, more particularly to control the diameter of thenanoparticles 14, the thickness of the depositedthin layer 12 as well as the temperature and time of the annealing step may be controlled or well-chosen. The optimal temperature and time to create thenanoparticles 14 depends on the type and the thickness of the depositedthin layer 12 of metal-free material. For example, the temperature for annealing may range between 500° C. and 800° C. The anneal step may be performed in a reactor. In the reactor, gases such as nitrogen and/or hydrogen can be used as ambient gases. - According to an alternative embodiment,
nanoparticles 14 which may, for example, comprise pure semiconductor material, e.g. pure Si, may be formed in a thin dielectric layer, e.g. a SiO2 layer, which is provided, e.g. deposited for example by CVD, onto thesubstrate 10, for example onto a semiconductor wafer, e.g. Si wafer. After deposition of the thin SiO2 layer a low energy Si ion implantation step may be performed on the SiO2 layer followed by an annealing step to create Si nanocrystals. A dissolving treatment, e.g. HF treatment (e.g. HF vapor or dilute solution), can then be applied to remove the SiO2 such thatSi nanoparticles 14 which are suitable for use as initiators of CNT growth are left on thesubstrate 10. - According to still other embodiments of the invention, the
substrate 10 onto which thenanoparticles 14 are formed or deposited, may be formed of a porous material. Examples of suitable porous materials to be used with embodiments of the present invention may be zeolites and porous low-k materials (commonly used in semiconductor processing and commercially available). Using porous material or in other words using asubstrate 10 having inner pores makes it possible to deposit thethin layer 12 not only on the major surface of thesubstrate 10 but also within these inner pores of thesubstrate 10. This significantly increases the surface area onto whichnanoparticles 14 can be formed. As a result the amount of CNTs which can be formed by the method according to embodiments of the invention may also significantly increase. - In case of such
porous substrates 10, athin layer 12 of, for example, semiconductor material, e.g. Si, the layer being continuous or non continuous, may be deposited onto a major surface of theporous substrate 10 and on the surface of the inner pores of theporous substrate 10. After performing of an annealing step as described above to create nanoparticles,nanoparticles 14 may be formed on the major surface of thesubstrate 10 and in the inner pores of thesubstrate 10. Thesenanoparticles 14 can then be used as catalysts to grow CNTs. - According to yet another alternative embodiment, no substrate is used but bulk catalyst nanoparticles may be provided to grow CNTs. The bulk nanoparticles should be such that a carbon source gas is able to flow in between neighbouring nanoparticles such that, when the bulk catalyst nanoparticles are provided in a reactor, CNTs can be grown onto the catalyst nanoparticles (see further).
- According to embodiments of the invention, the
nanoparticles 14, e.g. semiconductor nanoparticles such as Si or Ge nanoparticles, can be pre-treated before growth of CNTs is started. An example of such a pre-treatment may be removal of a native oxide (e.g. SiO2 in case of Si nanoparticles) by means of, for example a HF dip (e.g. a dip in 2% HF for 5 minutes). - After formation of the
non-metal containing nanoparticles 14, thesubstrate 10 on which thenanoparticles 14 are formed, or according to alternative embodiments the bulk nanoparticles, are transferred to a suitable reactor chamber of a reactor such as a Chemical Vapor Deposition (CVD) reactor to grow the CNTs 16 (seestep 15 inFIG. 1 ). The CVD reactor can, for example, be a Plasma Enhanced CVD reactor or a Thermal CVD reactor. In the CVD reactor a carbon source gas is decomposed or cracked by heating it. Cracking the carbon source gas leads to formation of different carbon fragments such that these fragments can be recombined on the catalyst nanoparticles to form a CNT. Recombination thus takes place at a surface of the formednanoparticles 14, e.g. semiconductor comprising nanoparticles such as Si or Ge comprising nanoparticles. - Heating the carbon source gas may, according to embodiments of the invention, be done by using a hot filament, by using a plasma or by using a combination of a hot filament and a plasma. When using a hot filament for decomposing the carbon source gas, this hot filament may be located in the reactor chamber such that cracked or decomposed carbon species do not recombine before they have reached the catalyst nanoparticles so as to grow CNTs (see further). The hot filament may be a metallic filament and can comprise W (Tungsten) or Ta (Tantalum) and is kept at high temperatures. The height of the temperature depends on the carbon source used and needs to be high enough to crack the carbon source. For example, the temperature of the hot filament may be 950° C. or higher.
- During formation of reactive carbon fragments by decomposing the carbon source gas and during subsequent CNT growth, the temperature of the
catalyst nanoparticles 14 and/or thesubstrate 10 on which thecatalyst nanoparticles 14 are formed may be in the range of between 800° C. up to 1000° C. - According to embodiments of the invention, any suitable carbon source gas known by a person skilled in the art may be used. For example the carbon source gas may be a hydrocarbon source and may be a hydrocarbon gas having one (C1) up to three (C3) carbon atoms. Examples of suitable hydrocarbon gases to be used for CVD assisted CNT growth may be CH4, C2H4, C2H2 or C3H6. According to other embodiments, alternative carbon sources such as carbon oxide (CO) can also be used as a carbon source gas. The amount of carbon source gas used in the reactor chamber determines the growth, morphology and properties of CNTs formed. The amount of carbon gas and/or the amount of cracked carbon fragments in the reactor chamber should be sufficient, i.e. high enough, to achieve CNT growth but on the other hand should be low enough so as to avoid formation of amorphous carbon onto the catalyst nanoparticles as in that case no CNT growth will occur.
- The CVD reactor chamber may furthermore comprise an inert gas and hydrogen. The inert gas may, for example, be nitrogen. As an example the total flow of gasses in the CVD reactor during the step of forming
CNTs 16 may be around 4 l/min N2, 2 l/min H2 and 0.01 up to 1 l/min carbon gas such as e.g. C2H2. A suitable gas flow can be 4 l/min N2, 2 l/min H2 and 0.1 l/min carbon gas such as C2H2. - Examples of a simplified reactor which may be used to perform CNT growth according to embodiments of the present invention is schematically illustrated in
FIG. 2 andFIG. 3 . The difference betweenFIG. 2 andFIG. 3 is the location of thehot filament 2. The reactor comprises aquartz tube 6 in which thesubstrate 10 comprising thenanoparticles 14, e.g. semiconductor comprising nanoparticles such as Si or Ge comprising nanoparticles, is placed. Afurnace 3 is situated at the outside of thequartz tube 6 and is used to create an optimal reaction temperature within thequartz tube 6. With optimal temperature is meant a temperature at which CNT growth can take place. In the example given inFIG. 2 , ahot filament 2 is placed at the entrance orgas inlet 1 of the reactor such that the carbon source, e.g. carbon source gas is cracked into fragments which may then recombine on thenanoparticles 14 to formCNTs 16. According to other embodiments and as illustrated inFIG. 3 , thehot filament 2 may be located above thesubstrate 10. In the latter case, more extensive growth of CNTs may be obtained because in that case the cracked carbon species do not have to travel a long way to reach thecatalyst nanoparticles 14, and thus have a lower chance, with respect to the case illustrated inFIG. 2 , of recombining before having assisted in CNT growth. - To release the
CNTs 16 formed on thesubstrate 10, for, for example, bulk production ofCNTs 16, a simple release process such as, for example, chemical dissolution of thesubstrate 10 can be done. - Hereinafter, some examples will be described. It has to be understood that these are only for the ease of understanding the present invention and are not intended to limit the invention in any way.
- 1. Nanoparticles Preparation
- A silicon wafer was provided as a
substrate 10 to grow theCNTs 16 on. Onto thesilicon substrate 10, first a Si3N4 barrier layer 11 was deposited in a vacuum reactor. Onto the Si3N4 barrier layer 11 athin layer 12 of 5 nm poly-Si was deposited. Without breaking the vacuum the sample was annealed in conditions such that thethin layer 12 broke intonanoparticles 14. The anneal step to break up the poly-Si layer 12 intoSi nanoparticles 14 was performed at 530° C. during a time period of 20 minutes. The obtainedSi nanoparticles 14 had a diameter of approximately 5 nm. - 2. Catalyst Nanoparticle Pre-treatment
- The
substrate 10 with thenanoparticles 14 on was then placed in a standard HF solution (2% HF) for a couple of minutes (e.g. 5 minutes) at room temperature so as to remove a possibly present native oxide formed after the nanoparticles have been exposed to air. Immediately after removal of the native oxide, thesubstrate 10 comprising theSi nanoparticles 14 was placed in a CVD reactor at 900° C. for 5 min. The reactor gases were N2 and H2 at a ratio of 4 l/min N2 to 4 l/min H2.The Si nanoparticles 14 were found to be suitable for growingCNTs 16 according to a method of embodiments of the present invention. By thenanoparticles 14 being suitable is meant that they can act as a template or precursor for CNT formation, in other words, that they can be used to initiate CNT growth. - 3. CNT Growth
- After formation of the
Si catalyst nanoparticles 14 in the CVD reactor, C2H2 gas was added to the reactor at a flow of 0.5 l/min. N2 and H2 were also present in the reactor chamber during CNT growth at a ratio of 4 l/min N2 to 2 l/min H2. The substrate temperature was in the range of between 800° C. and 1000° C., for example 900° C. - During CNT growth a W or
Ta filament 2, situated at theentrance 1 of the gas inlet of the reactor, was heated such that incoming C2H2 gas was cracked into different carbon fragments such as C—C, C—H, CH3• radicals, as well as stable species like CH4 or C2H2. The filament temperature was around 950° C. (filament current was 6½-6¾ A).FIG. 4 illustrates a scanning electron microscopy (SEM) picture of CNTs grown onto Si catalyst nanoparticles. It can be seen fromFIG. 4 that, in the experiment conducted, nanotubes are grown at a pm scale distance. - 4. Massive CNT Growth
- Before performing CNT growth, the
substrates 10 withnanoparticles 14 on were etched in HF (2%) for 1 min. at room temperature in order to remove a possibly present native oxide from theSi nanoparticles 14. - The samples were placed in the CVD reactor chamber with temperatures ranging between 600° C. and 9000° C., under reducing atmosphere in N2:H2 (4:2 l/min.) for 5 minutes at atmospheric pressure.
- A W wire was used as a
hot filament 2 and was located above thesubstrate 10 comprising thecatalyst nanoparticles 14. A flow of 0.1 l/min. of acetylene, ethylene or methane in addition to the other gases (N2:H2) was flown over thehot filament 2 such that the Carbon source gas was cracked. The gas composition used for this experiment was N2:H2:C at a ratio 4:2:0.1 l/min. The Carbon source used was either one of acetylene, ethylene or methane. TheCNTs 16 were grown for half an hour at atmospheric pressure. -
FIG. 5 andFIG. 6 illustrate SEM pictures after growth of CNTs onto the Si nanoparticles according to embodiments of the present example. Massive growth ofCNTs 16 was observed, i.e. CNTs were grown much closer to each other when compared toFIG. 4 . A more intensive growth was observed in the area where the Si nanoparticles are closer to the hot filament 2 (see upper row ofCNTs 16 inFIG. 5 ). - It is to be understood that although preferred embodiments, specific constructions and configurations, as well as materials, have been discussed herein for devices according to the present invention, various changes or modifications in form and detail may be made without departing from the scope of this invention as defined by the appended claims.
Claims (19)
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US12/441,132 US20100047152A1 (en) | 2006-09-21 | 2007-09-21 | Growth of carbon nanotubes using metal-free nanoparticles |
Applications Claiming Priority (3)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US84655806P | 2006-09-21 | 2006-09-21 | |
US12/441,132 US20100047152A1 (en) | 2006-09-21 | 2007-09-21 | Growth of carbon nanotubes using metal-free nanoparticles |
PCT/BE2007/000109 WO2008034204A2 (en) | 2006-09-21 | 2007-09-21 | Growth of carbon nanotubes using metal-free nanoparticles |
Publications (1)
Publication Number | Publication Date |
---|---|
US20100047152A1 true US20100047152A1 (en) | 2010-02-25 |
Family
ID=39200861
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
US12/441,132 Abandoned US20100047152A1 (en) | 2006-09-21 | 2007-09-21 | Growth of carbon nanotubes using metal-free nanoparticles |
Country Status (4)
Country | Link |
---|---|
US (1) | US20100047152A1 (en) |
EP (1) | EP2069234A2 (en) |
JP (1) | JP2010504268A (en) |
WO (1) | WO2008034204A2 (en) |
Cited By (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO2014151144A1 (en) * | 2013-03-15 | 2014-09-25 | Seerstone Llc | Carbon oxide reduction with intermetallic and carbide catalysts |
US9586823B2 (en) | 2013-03-15 | 2017-03-07 | Seerstone Llc | Systems for producing solid carbon by reducing carbon oxides |
US9783416B2 (en) | 2013-03-15 | 2017-10-10 | Seerstone Llc | Methods of producing hydrogen and solid carbon |
US10086349B2 (en) | 2013-03-15 | 2018-10-02 | Seerstone Llc | Reactors, systems, and methods for forming solid products |
US10115844B2 (en) | 2013-03-15 | 2018-10-30 | Seerstone Llc | Electrodes comprising nanostructured carbon |
US11752459B2 (en) | 2016-07-28 | 2023-09-12 | Seerstone Llc | Solid carbon products comprising compressed carbon nanotubes in a container and methods of forming same |
Families Citing this family (8)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
FR2937895A1 (en) * | 2008-11-04 | 2010-05-07 | Commissariat Energie Atomique | MOLD COMPRISING A NANOSTRUCTURED SURFACE FOR MAKING NANOSTRUCTURED POLYMERIC PARTS AND METHOD FOR MANUFACTURING SUCH A MOLD |
US8257678B2 (en) | 2009-07-31 | 2012-09-04 | Massachusetts Institute Of Technology | Systems and methods related to the formation of carbon-based nanostructures |
WO2011066288A2 (en) * | 2009-11-25 | 2011-06-03 | Massachusetts Institute Of Technology | Systems and methods for enhancing growth of carbon-based nanostructures |
US9663368B2 (en) | 2010-10-28 | 2017-05-30 | Massachusetts Institute Of Technology | Carbon-based nanostructure formation using large scale active growth structures |
US20130072077A1 (en) | 2011-09-21 | 2013-03-21 | Massachusetts Institute Of Technology | Systems and methods for growth of nanostructures on substrates, including substrates comprising fibers |
US9440855B2 (en) * | 2012-02-13 | 2016-09-13 | Osaka University | High purity carbon nanotube, process for preparing the same and transparent conductive film using the same |
WO2014134484A1 (en) | 2013-02-28 | 2014-09-04 | N12 Technologies, Inc. | Cartridge-based dispensing of nanostructure films |
CN113213454B (en) * | 2021-04-21 | 2022-06-24 | 温州大学 | Method for preparing single-walled carbon nanotube by taking graphene as catalyst |
Citations (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US20040071870A1 (en) * | 1999-06-14 | 2004-04-15 | Knowles Timothy R. | Fiber adhesive material |
US20050207964A1 (en) * | 2004-03-22 | 2005-09-22 | Dojin Kim | Method for synthesizing carbon nanotubes |
US20060133982A1 (en) * | 2002-11-14 | 2006-06-22 | Cambridge University Technical Services Limited | Method for producing carbon nanotubes and/or nanofibres |
Family Cites Families (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
CN1239387C (en) * | 2002-11-21 | 2006-02-01 | 清华大学 | Carbon nano transistor array and grwoth method thereof |
GB0426863D0 (en) * | 2004-12-07 | 2005-01-12 | Univ Southampton | Method of manufacturing carbon nanotubes |
-
2007
- 2007-09-21 WO PCT/BE2007/000109 patent/WO2008034204A2/en active Application Filing
- 2007-09-21 JP JP2009528558A patent/JP2010504268A/en active Pending
- 2007-09-21 EP EP07815688A patent/EP2069234A2/en not_active Withdrawn
- 2007-09-21 US US12/441,132 patent/US20100047152A1/en not_active Abandoned
Patent Citations (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US20040071870A1 (en) * | 1999-06-14 | 2004-04-15 | Knowles Timothy R. | Fiber adhesive material |
US20060133982A1 (en) * | 2002-11-14 | 2006-06-22 | Cambridge University Technical Services Limited | Method for producing carbon nanotubes and/or nanofibres |
US20050207964A1 (en) * | 2004-03-22 | 2005-09-22 | Dojin Kim | Method for synthesizing carbon nanotubes |
Cited By (9)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO2014151144A1 (en) * | 2013-03-15 | 2014-09-25 | Seerstone Llc | Carbon oxide reduction with intermetallic and carbide catalysts |
US20160031710A1 (en) * | 2013-03-15 | 2016-02-04 | Seerstone Llc | Carbon oxide reduction with intermetallic and carbide catalysts |
US9586823B2 (en) | 2013-03-15 | 2017-03-07 | Seerstone Llc | Systems for producing solid carbon by reducing carbon oxides |
US9783416B2 (en) | 2013-03-15 | 2017-10-10 | Seerstone Llc | Methods of producing hydrogen and solid carbon |
US9783421B2 (en) * | 2013-03-15 | 2017-10-10 | Seerstone Llc | Carbon oxide reduction with intermetallic and carbide catalysts |
US10086349B2 (en) | 2013-03-15 | 2018-10-02 | Seerstone Llc | Reactors, systems, and methods for forming solid products |
US10115844B2 (en) | 2013-03-15 | 2018-10-30 | Seerstone Llc | Electrodes comprising nanostructured carbon |
US11752459B2 (en) | 2016-07-28 | 2023-09-12 | Seerstone Llc | Solid carbon products comprising compressed carbon nanotubes in a container and methods of forming same |
US11951428B2 (en) | 2016-07-28 | 2024-04-09 | Seerstone, Llc | Solid carbon products comprising compressed carbon nanotubes in a container and methods of forming same |
Also Published As
Publication number | Publication date |
---|---|
EP2069234A2 (en) | 2009-06-17 |
WO2008034204A2 (en) | 2008-03-27 |
WO2008034204A3 (en) | 2008-11-27 |
JP2010504268A (en) | 2010-02-12 |
Similar Documents
Publication | Publication Date | Title |
---|---|---|
US20100047152A1 (en) | Growth of carbon nanotubes using metal-free nanoparticles | |
KR100376197B1 (en) | Low temperature synthesis of carbon nanotubes using metal catalyst layer for decompsing carbon source gas | |
US6350488B1 (en) | Mass synthesis method of high purity carbon nanotubes vertically aligned over large-size substrate using thermal chemical vapor deposition | |
US7491269B2 (en) | Method for catalytic growth of nanotubes or nanofibers comprising a NiSi alloy diffusion barrier | |
Shalav et al. | ${\bf SiO} _ {\bm x} $ Nanowires Grown via the Active Oxidation of Silicon | |
TW201723219A (en) | Metal free graphene synthesis on insulating or semiconducting substrates | |
JP2006036593A (en) | Method and apparatus for manufacturing monolayer carbon nanotube | |
KR101626776B1 (en) | Method for synthesizing graphene using benzene | |
CN113213454A (en) | Method for preparing single-walled carbon nanotube by taking graphene as catalyst | |
JP2007284336A (en) | Method for growing carbon nanotube and method for manufacturing carbon nanotube structure | |
Hesamzadeh et al. | PECVD-growth of carbon nanotubes using a modified tip-plate configuration | |
JP5154801B2 (en) | Method for producing a material layer on a support | |
US20150147525A1 (en) | Method for enhancing growth of carbon nanotubes on substrates | |
KR100382878B1 (en) | Synthesis method of highly purified carbon nanotubes | |
Kim et al. | Self-assembled growth and luminescence of crystalline Si/SiOx core–shell nanowires | |
KR101315763B1 (en) | Vertical alignment method of carbon nanotube array | |
JP4545530B2 (en) | Method for producing fine carbon fiber | |
López-Camacho et al. | The key role of hydrogen in the growth of SiC/SiO2 nanocables | |
KR100372332B1 (en) | Massive synthesis method of purified carbon nanotubes vertically aligned on large-area substrate using the thermal chemical vapor deposition | |
KR20010029644A (en) | Method of fabricating carbon nanotube | |
JP2007284311A (en) | Manufacturing method of carbon nano-material | |
CN115613162B (en) | Composite fiber and preparation method thereof | |
JP4838990B2 (en) | Method for producing carbon nanotube | |
TWI408246B (en) | Manufacturing method for branched carbon nanotubes | |
US20030111336A1 (en) | Large area silicon cone arrays fabrication and cone based nanostructure modification |
Legal Events
Date | Code | Title | Description |
---|---|---|---|
AS | Assignment |
Owner name: INTERUNIVERSITAIR MICROELEKTRONICA CENTRUM (IMEC) Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:WHELAN, CAROLINE;ESCONJAUREGUI, SANTIAGO CRUZ;SIGNING DATES FROM 20090301 TO 20090313;REEL/FRAME:022455/0179 |
|
AS | Assignment |
Owner name: INTERUNIVERSITAIR MICROELEKTRONICA CENTRUM (IMEC) Free format text: CORRECTIVE ASSIGNMENT TO RE-RECORD ASSIGNMENT PREVIOUSLY RECORDED UNDER REEL AND FRAME 022455/0179 TO CORRECT THE ASSIGNEES TO ADDITIONALLY INCLUDE NANOCYL SA;ASSIGNORS:WHELAN, CAROLINE;ESCONJAUREGUI, SANTIAGO CRUZ;SIGNING DATES FROM 20090301 TO 20090313;REEL/FRAME:022533/0007 Owner name: NANOCYL SA,BELGIUM Free format text: CORRECTIVE ASSIGNMENT TO RE-RECORD ASSIGNMENT PREVIOUSLY RECORDED UNDER REEL AND FRAME 022455/0179 TO CORRECT THE ASSIGNEES TO ADDITIONALLY INCLUDE NANOCYL SA;ASSIGNORS:WHELAN, CAROLINE;ESCONJAUREGUI, SANTIAGO CRUZ;SIGNING DATES FROM 20090301 TO 20090313;REEL/FRAME:022533/0007 |
|
AS | Assignment |
Owner name: INTERUNIVERSITAIR MICROELEKTRONICA CENTRUM (IMEC) Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:NANOCYL SA;REEL/FRAME:022691/0480 Effective date: 20090423 |
|
AS | Assignment |
Owner name: IMEC,BELGIUM Free format text: "IMEC" IS AN ALTERNATIVE OFFICIAL NAME FOR "INTERUNIVERSITAIR MICROELEKTRONICA CENTRUM VZW";ASSIGNOR:INTERUNIVERSITAIR MICROELEKTRONICA CENTRUM VZW;REEL/FRAME:024200/0675 Effective date: 19840318 Owner name: IMEC, BELGIUM Free format text: "IMEC" IS AN ALTERNATIVE OFFICIAL NAME FOR "INTERUNIVERSITAIR MICROELEKTRONICA CENTRUM VZW";ASSIGNOR:INTERUNIVERSITAIR MICROELEKTRONICA CENTRUM VZW;REEL/FRAME:024200/0675 Effective date: 19840318 |
|
AS | Assignment |
Owner name: KATHOLIEKE UNIVERSITEIT LEUVEN, K.U. LEUVEN R&D, B Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:IMEC;REEL/FRAME:026914/0218 Effective date: 20110913 |
|
STCB | Information on status: application discontinuation |
Free format text: ABANDONED -- FAILURE TO RESPOND TO AN OFFICE ACTION |