# US 7,744,958 B2 · Method for making carbon nanotube-based device > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 7,744,958 B2 - Document ID: US7744958B2 - Status: Granted - Kind: B2 - Application number: 11/416,748 - Filed: 2006-05-03 - Published: 2007-03-29 - Granted: 2010-06-29 - Earliest claimed: 2005-07-13 - Assignees: Tsinghua University; Hon Hai Precision Industry Co., Ltd. - Inventors: Liang Liu; Shou-Shan Fan - Web page: https://patentgrep.com/patent/US7744958B2 ## CPC - C01B 32/162: characterised by catalysts - B82Y 30/00: Nanotechnology for materials or surface science, e.g. nanocomposites - B82Y 40/00: Manufacture or treatment of nanostructures - C01B 2202/08: Aligned nanotubes - Y10S 977/84: Manufacture, treatment, or detection of nanostructure - Y10S 977/843: Gas phase catalytic growth, i.e. chemical vapor deposition - Y10S 977/89: Deposition of materials, e.g. coating, cvd, or ald - C01B: NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; {METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C} - B82Y: SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES - Y10S: TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS ## Abstract A method for making a carbon nanotube-based device is provided. A substrate with a shadow mask layer formed thereon is provided, to define an unmasked surface area on the substrate. The substrate is rotated around an axis. A catalyst layer including at least one catalyst block is formed on the unmasked surface area of the substrate. A thickness of the at least one catalyst block is decreased gradually from a first end thereof to an opposite second end thereof, and somewhere the at least one catalyst block having a region with a thickness proximal or equal to an optimum thickness at which carbon nanotubes growing fastest. A carbon source gas is introduced. At least one carbon nanotube array extending from the catalyst layer using a chemical vapor deposition process is formed. The at least one carbon nanotube array is arc-shaped, and bend in a direction of deviating from the region. ## Claims ### Claim 1 A method for making a carbon nanotube-based device, the method comprising the steps of: providing a substrate with a shadow mask layer formed thereon, the shadow mask layer being configured for defining an unmasked surface area on the substrate; rotating the substrate around an axis; forming a catalyst layer comprising at least one catalyst block on the unmasked surface area of the substrate, a thickness of the at least one catalyst block being gradually decreased from a first end thereof to an opposite second end thereof, and the at least one catalyst block having a region with a thickness proximal or equal to an optimum thickness at which carbon nanotubes grow the fastest, a thicker region having a thickness that is thicker than the optimum thickness, and a thinner region having a thickness that is thinner than the optimum thickness, such that the carbon nanotubes in the thicker and thinner regions grow slower than the carbon nanotubes at the region; introducing a carbon source gas; and forming at least one carbon nanotube array extending from the catalyst layer using a chemical vapor deposition process, wherein the at least one carbon nanotube array comprises of at least two arc-shaped sections, and each section bending in a direction deviating from the region. ### Claim 2 (depends on 1) The method of claim 1, wherein the step of forming the catalyst layer on the substrate comprising the sub-steps of: disposing a catalyst source on a same side of the substrate with the shadow mask, the catalyst source being configured for supplying a catalyst material and depositing the catalyst material onto the unmasked surface area of the substrate, and a distance from the catalyst source to the axis being larger than a distance from the axis to the substrate; depositing the catalyst material on the substrate by evaporating the catalyst material of the catalyst source, to form an initial catalyst layer; removing the shadow mask layer from the substrate; and defining the initial catalyst layer in a pattern, to form the catalyst layer. ### Claim 3 (depends on 2) The method of claim 2, further comprising a step of marking the region of the initial catalyst layer, before defining the initial catalyst layer in a pattern. ### Claim 4 (depends on 2) The method of claim 2, wherein the catalyst source is selected from the group consisting of a point evaporating source, and a linear evaporating source. ### Claim 5 (depends on 4) The method of claim 4, wherein the linear evaporating source is disposed along the axis. ### Claim 6 (depends on 2) The method of claim 2, wherein the catalyst material is selected from the group consisting of iron, cobalt, nickel, and alloys thereof. ### Claim 7 (depends on 2) The method of claim 2, wherein a distance from the catalyst source to the substrate is no less than ten times the size of the substrate. ### Claim 8 (depends on 7) The method of claim 7, wherein a duration time of depositing the catalyst material is no less than ten times a rotation period of the substrate. ### Claim 9 (depends on 7) The method of claim 7, wherein the shadow mask layer has a plurality of sidewalls substantially perpendicular to the substrate. ### Claim 10 (depends on 9) The method of claim 9, wherein a thickness of a position of the initial catalyst layer distant from the shadow mask layer with a distance of λ satisfies the condition: T(λ)=T0/2×(1+λ/√{square root over (λ2+h2)}) where, the T(λ) is a thickness of the position of the initial catalyst layer distant from the shading masking layer with a distance of λ, T0 is a thickness of the position under a situation that no shadow mask layer formed on the substrate during a process of depositing the catalyst material; h is a height of the shadow mask layer. ### Claim 11 (depends on 1) The method of claim 1, wherein a thickness of the first end of the at least one catalyst block is in the range from 5 to 20 nanometers; a thickness of the second end of the at least one catalyst block is in the range from 1 to 10 nanometers. ### Claim 12 (depends on 1) The method of claim 1, wherein the axis is substantially parallel to the substrate. ### Claim 13 (depends on 1) The method of claim 1, wherein the shadow mask layer is made from a material selected from the group consisting of a photo-resist, a metal, a metallic oxide, and a metallic nitride. ### Claim 14 (depends on 1) The method of claim 1, wherein the step of forming the catalyst layer on the substrate comprising the sub-steps of: disposing a catalyst source beside the substrate, the catalyst source being configured for supplying a catalyst material and radially depositing the catalyst material onto the substrate, and a distance from the catalyst source to the axis being larger than a distance from the axis to the substrate; depositing the catalyst material on the substrate by evaporating the catalyst material of the catalyst source to form the catalyst layer; and removing the shadow mask layer from the substrate. ### Claim 15 (depends on 1) The method of claim 1, further comprising a step of annealing the substrate with the catalyst layer in an oxygen-containing environment, to form nano-sized catalyst oxide particles, before introducing the carbon source gas. ### Claim 16 (depends on 1) The method of claim 1, wherein the optimum thickness of the catalyst layer for growing carbon nanotubes is about 5 nanometers. ### Claim 17 A method for making a carbon nanotube-based device, the method comprising: providing a substrate with an integrated shadow mask layer formed thereon, the shadow mask layer being configured for defining an unmasked surface area on the substrate; rotating the substrate around an axis continuously; forming a catalyst layer comprising at least two catalyst blocks on the unmasked surface area of the substrate, a thickness of the at least two catalyst blocks being gradually decreased from a first end thereof to an opposite second end thereof, and the at least two catalyst blocks having a region with a thickness proximal or equal to an optimum thickness at which carbon nanotubes grow the fastest, a thicker region having a thickness that is thicker than the optimum thickness, and a thinner region having a thickness that is thinner than the optimum thickness, the at least two catalyst blocks being staggeringly positioned at opposite sides of the region; introducing a carbon source gas; and forming at least two carbon nanotube arrays extending from the catalyst layer using a chemical vapor deposition process, wherein the at least two carbon nanotube arrays being arc-shaped, and bending in opposite directions deviating from the region. ### Claim 18 (depends on 17) The method of claim 17, wherein a thinnest one of the at least two catalyst blocks has a thickness proximal or equal to the optimum thickness, and a thickest end of the other of the at least two catalyst blocks has a thickness proximal or equal to the optimum thickness.