Carbon nanotube with ZnO asperities

• US 7,462,499 B2
• Filed: 10/28/2005
• Issued: 12/09/2008
• Est. Priority Date: 10/28/2005
• Status: Expired due to Fees

• Current Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.)
• Original Assignee: Sharp Laboratories of America Incorporated (Hon Hai Precision Industry Co., Ltd.)
• Inventors: Hsu, Sheng Teng, Ono, Yoshi, Conley, John F. Jr., Stecker, Lisa H., Jiao, Jun, Dong, Lifeng, Green, Josh M.
• Primary Examiner(s): Baumeister; Bradley W.
• Assistant Examiner(s): Reames; Matthew L
• Application Number:
  US11/262,439
• Publication Number:
  US 20070099441A1
• Time in Patent Office: 1,138 Days
• Field of Search: 438/20, 977/754
• US Class Current: 438/20
• CPC Class Codes: B82Y 10/00 Nanotechnology for information processing, storage or transmission, e.g. quantum computing or single electron logic
• CPC Class Codes: B82Y 30/00 Nanotechnology for materials or surface science, e.g. nanocomposites
• CPC Class Codes: B82Y 40/00 Manufacture or treatment of nanostructures
• CPC Class Codes: C01B 2202/34 Length
• CPC Class Codes: C01B 2202/36 Diameter
• CPC Class Codes: C01B 32/162 characterised by catalysts
• CPC Class Codes: C01B 32/168 After-treatment
• CPC Class Codes: H01J 1/304 Field-emissive cathodes
• CPC Class Codes: H01J 2201/30469 Carbon nanotubes (CNTs)
• CPC Class Codes: H01J 9/025 of field emission cathodes
• CPC Class Codes: H01L 21/0237 Materials
• CPC Class Codes: H01L 21/02381 Silicon, silicon germanium, germanium
• CPC Class Codes: H01L 21/02444 Carbon, e.g. diamond-like carbon
• CPC Class Codes: H01L 21/02472 Oxides
• CPC Class Codes: H01L 21/02483 Oxide semiconducting materials not being Group 12/16 materials, e.g. ternary compounds
• CPC Class Codes: H01L 21/02513 Microstructure
• CPC Class Codes: H01L 21/02554 Oxides
• CPC Class Codes: H01L 21/02601 Nanoparticles fullerenes H10K85/211
• CPC Class Codes: Y10S 977/754 Dendrimer, i.e. serially branching or "tree-like" structure

Abstract

A ZnO asperity-covered carbon nanotube (CNT) device has been provided, along with a corresponding fabrication method. The method comprises: forming a substrate; growing CNTs from the substrate; conformally coating the CNTs with ZnO; annealing the ZnO-coated CNTs; and, forming ZnO asperities on the surface of the CNTs in response to the annealing. In one aspect, the ZnO asperities have a density in the range of about 100 to 1000 ZnO asperities per CNT. The density is dependent upon the deposited ZnO film thickness and annealing parameters. The CNTs are conformally coating with ZnO using a sputtering, chemical vapor deposition (CVD), spin-on, or atomic layer deposition (ALD). For example, an ALD process can be to deposit a layer of ZnO over the CNTs having a thickness in the range of 1.2 to 200 nanometers (nm).

Claims

1. A method for fabricating a nanotube with ZnO asperities, the method comprising:

forming a substrate;

growing carbon nanotubes (CNTs), with a surface, from the substrate;

conformally coating the CNTs with ZnO;

annealing the ZnO-coated CNTs; and

,

forming ZnO asperities on the surface of the CNTs in response to the annealing.

2. The method of claim 1 wherein forming ZnO asperities on the surface of the CNTs includes forming a ZnO asperity density in the range of about 100 to 1000 ZnO asperities per CNT.

3. The method of claim 1 wherein forming the substrate includes implanting an n+ dopant in a Si substrate, forming an n+ layer of Si substrate.

4. The method of claim 3 wherein conformally coating the CNTs with ZnO includes depositing ZnO using a deposition process selected from the group consisting of sputtering, chemical vapor deposition (CVD), spin-on, and atomic layer deposition (ALD).

5. The method of claim 1 wherein conformally coating the CNTs with ZnO includes using an ALD process to deposit a layer of ZnO over the CNTs having a thickness in the range of 1.2 to 200 nanometers (nm).

6. The method of claim 1 wherein annealing the ZnO-coated CNTs includes:

heating the substrate to a temperature in the range of about 400 to 950°

C.;

exposing the ZnO-coated CNTs to an inert gas environment, selected from the group consisting of N₂, Ar, and He; and

,

exposing the ZnO-coated CNTs for a duration in the range of about 10 to 300 seconds.

7. The method of claim 1 wherein forming ZnO asperities on the surface of the CNTs includes agglomerating the ZnO into nanoparticles.

8. The method of claim 1 wherein forming the substrate includes forming a substrate from a material selected from the group consisting of Si, sapphire, SiC, quartz, glass, and plastic.

9. The method of claim 1 wherein growing CNTs from the substrate includes growing CNTs selected from the group consisting of single and multi-walled CNTs.

10. The method of claim 1 wherein growing CNTs includes growing CNTs having a diameter in the range of about 1 nm to 100 nm.

11. The method of claim 1 wherein growing CNTs from the substrate includes growing CNTs as follows:

heating the substrate to a temperature of about 700°

C.; and

,

using Fe to catalyze the decomposition of acetylene (C₂H₂).

12. The method of claim 1 wherein growing CNTs from the substrate includes growing CNTs having a minimum length in the range of about 20 to 100 nm and a maximum length of about 100 micrometers.

13. The method of claim 1 wherein growing CNTs from the substrate includes growing CNTs having a diameter of about 60 nm and having a length;

wherein conformally coating the CNTs with ZnO includes coating the CNTs with a ZnO layer of about 10 nm; and

,

wherein forming ZnO asperities on the surface of the CNTs includes forming one ZnO asperity about every 20 nm, along the length of a CNT.

14. The method of claim 13 wherein forming ZnO asperities on the surface of the CNTs includes forming ZnO asperities, each having a surface area of about 3600 square-nanometers and a volume of about 33,000 cubic nanometers.

15. The method of claim 1 wherein conformally coating the CNTs with ZnO includes decreasing the thickness of the deposited ZnO;

and,

wherein forming ZnO asperities on the surface of the CNTs includes decreasing the distance between ZnO asperities, and decreasing the volume of each ZnO asperity, in response to decreasing the ZnO thickness.