# US 2013/0156679 A1 · Method and apparatus for forming nanoparticles > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2013/0156679 A1 - Document ID: US20130156679A1 - Status: Published application - Kind: A1 - Application number: 13/811,645 - Filed: 2011-07-19 - Published: 2013-06-20 - Earliest claimed: 2010-07-19 - Assignees: Cambridge Enterprise Limited - Inventors: John Robertson; C. Santiago Esconjauregui - Web page: https://patentgrep.com/patent/US20130156679A1 ## CPC - B01J 37/0221: {of particles} - B01J 19/088: {giving rise to electric discharges (for heating purposes H05B7/00; for the production of ozone C01B13/11, H01T19/00)} - B01J 23/74: Iron group metals - B01J 23/745: Iron - B01J 23/75: Cobalt - B01J 23/755: Nickel - B01J 23/881: and iron - B01J 23/882: and cobalt - B01J 23/883: and nickel - B01J 35/393: {Metal or metal oxide crystallite size} - B01J 35/395: {Thickness of the active catalytic layer} - B01J 37/0201: {Impregnation} - B01J 37/0205: {in several steps} - B01J 37/0238: {via the gaseous phase-sublimation} - B01J 37/024: {Multiple impregnation or coating} - B01J 37/0244: {Coatings comprising several layers} - B01J 37/08: Heat treatment {(B01J37/0009, B01J37/0018 take precedence)} - B01J 37/12: Oxidising - B01J 37/18: with gases containing free hydrogen - B01J 37/349: {making use of flames, plasmas or lasers} - B82Y 30/00: Nanotechnology for materials or surface science, e.g. nanocomposites - B82Y 40/00: Manufacture or treatment of nanostructures - C01B 32/162: characterised by catalysts - B01J 2235/00: Indexing scheme associated with group B01J35/00, related to the analysis techniques used to determine the catalysts form or properties - B01J: CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS - B82Y: SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES - C01B: NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; {METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C} ## Abstract A first layer of a catalyst material is formed on a substrate and heat treated to form a first plurality of nanoparticles. A second layer of a catalyst material is then formed over the substrate and the first plurality of nanoparticles and heat treated to form a second plurality of nanoparticles. The first layer of nanoparticles is advantageously not affected by the deposition or heat treatment of the second layer of catalyst material, for example being pinned or immobilised, optionally by oxidation, before formation of the second layer. ## Claims ### Claim 1 A method for fabricating catalyst nanoparticles to serve as growth nuclei for carbon nanotubes (CNTs), comprising the steps of: (A) forming a layer of a catalyst material over a substrate, and heat treating the layer to form a plurality of catalyst nanoparticles; and (B) forming a further layer of catalyst material over the substrate and the catalyst nanoparticles, and heat treating the further layer to form a further plurality of catalyst nanoparticles. ### Claim 2 (depends on 1) A method according to claim 1, in which step (B) is repeated to form one or more additional further pluralities of nanoparticles. ### Claim 3 (depends on 1) A method according to claim 1, in which each layer of catalyst material is of less than 1 nm average thickness. ### Claim 4 (depends on 1) A method according to any preceding claim 1, in which at least one or more of the layer and the further layers are is not closed. ### Claim 5 (depends on 1) A method according to any preceding claim 1, in which the layer and the further layer(s) are of the same material. ### Claim 6 (depends on 1, 2, 3, 4) A method according to any of claims 1 to 4, in which the layer and the further layer(s) are not of the same material. ### Claim 7 (depends on 1) A method according to any preceding claim 1, in which at least one of the layer and the further layer(s) is a composite layer comprising more than one sub-layer. ### Claim 8 (depends on 1) A method according to any preceding claim 1, in which at least 90% of the nanoparticles are of less than 2 nm diameter. ### Claim 9 (depends on 1) A method according to any preceding claim 1, in which the catalyst material comprises Fe, Co or Ni. ### Claim 10 (depends on 1) A method according to any preceding claim 1, in which the substrate comprises a material selected from the group consisting of alumina, silica, silica following an oxidising pre-treatment, metal silicides and metal nitrides. ### Claim 11 (depends on 1) A method according to any preceding claim 1 for forming nanoparticles over the substrate at a density equal to or greater than 5×1012 cm2 or 1013 cm2, or preferably 5×13 cm2, or particularly preferably 1014 cm2. ### Claim 12 (depends on 1) A method according to any preceding claim 1, in which each heat treatment heat treating includes a step of increasing temperature to a predetermined annealing temperature, and in which the rate of the temperature increase is higher in step (A) than in step (B). ### Claim 13 (depends on 1) A method according to any preceding claim 1, including the step of exposing the substrate and the nanoparticles formed over the substrate to an oxidizing or nitriding atmosphere, such as a plasma, or an atmosphere containing surphur or sulphides, before the formation of the further layer of catalyst material. ### Claim 14 (depends on 13) A method according to claim 13, in which the exposure to the oxidizing or other atmosphere nitriding occurs during the heat treatment to form the nanoparticles. ### Claim 15 (depends on 13, 14) A method according to claim 13 or 14, including the step of depositing a layer comprising a material selected from the group comprising Al, Ti, Cr, Zr and Hf over the substrate and the nanoparticles formed over the substrate, and then exposing the deposited layer to an oxidising atmosphere. ### Claim 16 (depends on 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15) A substrate provided with catalyst nanoparticles to serve as growth nuclei for carbon nanotubes, fabricated using a method as defined in any of claims 1 to 15. ### Claim 17 An electronic device comprising a conducting element formed from carbon nanotubes grown on a substrate provided with catalyst nanoparticles, in which the nanoparticles are fabricated as defined in any of claim(s) 1 to 15. ### Claim 18 A substrate provided with catalyst nanoparticles to serve as growth nuclei for carbon nanotubes, in which the nanoparticles comprise first and second pluralities of nanoparticles formed over the same substrate. ### Claim 19 An electronic device comprising a conducting element formed from carbon nanotubes grown on a substrate provided with catalyst nanoparticles, in which the nanoparticles comprise first and second pluralities of nanoparticles formed over the same substrate. ### Claim 20 An apparatus for fabricating catalyst nanoparticles to serve as growth nuclei for carbon nanotubes, comprising: a reactor for forming a layer of a catalyst material over a substrate; a heater for heat treating the layer of catalyst material to form a plurality of catalyst nanoparticles; and a controller for controlling the apparatus to repeat the formation of layers of catalyst material and the heat treatment to form one or more further pluralities of catalyst nanoparticles. ### Claim 21 (depends on 20) An apparatus according to claim 20, further comprising: an oxidation apparatus for exposing the substrate and any nanoparticles already formed over the substrate to an oxidizing or nitriding atmosphere, such as a plasma, or an atmosphere containing sulphur or sulphides, before the formation of the second and any subsequent layers of catalyst material. ### Claim 22 (depends on 21) An apparatus according to claim 21, further comprising: an intermediate reactor for depositing a layer of a material selected from the group comprising Al, Ti, Cr, Zr and Hf over the substrate and any nanoparticles already formed over the substrate before each exposure to the oxidising atmosphere. ### Claim 23 (canceled) ### Claim 24 (canceled) ### Claim 25 (canceled) ### Claim 26 (depends on 2) A method according to claim 2, in which each layer of catalyst material is of less than 1 nm average thickness. ### Claim 27 (depends on 2) A method according to claim 2, in which at least one layer is not closed. ### Claim 28 (depends on 2) A method according to claim 2, in which the layer and the further layer are of the same material. ### Claim 29 (depends on 2) A method according to claim 2, in which the layer and the further layer are not of the same material. ### Claim 30 (depends on 2) A method according to claim 2, in which at least one of the layer and the further layer is a composite layer comprising more than one sub-layer. ### Claim 31 (depends on 2) A method according to claim 2, in which at least 90% of the nanoparticles are of less than 2 nm diameter.