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Plasma CVD Carbon Nanotubes

Plasma CVD Carbon Nanotubes. Instructor: Yonhua Tzeng An-Jen Cheng February 25 2004. Questions. What are the advantages of plasma in growing carbon nanotubes? How can we change the carbon nanotubes’ properties?. Introduction.

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Plasma CVD Carbon Nanotubes

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  1. Plasma CVD Carbon Nanotubes Instructor: Yonhua Tzeng An-Jen Cheng February 25 2004

  2. Questions • What are the advantages of plasma in growing carbon nanotubes? • How can we change the carbon nanotubes’ properties?

  3. Introduction • Carbon nanotubes are synthesized in plasmas containing ionized carbon atoms. • Many materials are composed by carbon such as: diamond, graphite and so on • Carbon nanotubes have preeminent electric, thermal, and mechanical properties such as high aspect ratio, high stress, high resistance to chemical and physics attack.

  4. Structures of carbon nanotubes • Carbon nanotubes • 1.Single-walled carbon nanotube http://www.applied-nanotech.com http://www.fundp.ac.be/~amayer/Gallery.html

  5. 2.Multi-walled carbon nanotubes http://www.fundp.ac.be/~amayer/Gallery.html

  6. Methods to grow carbon nanotubes • 1.arc-discharge • 2.laser evaporation • 3.thermal CVD • 4.pyrolysis • 5.microwave plasma-enhanced chemical vapor deposition

  7. Advantages • Uniform films of vertically well-aligned carbon nanotubes have been grown using microwave plasma–enhanced CVD. • Microwave plasma-enhanced CVD allow carbon nanotubes to grow at lower temperature. • MW-PECVD can control the carbon nanotubes structures such as: diameter, growth rate and length more directly.

  8. RF Sputtering system http://www.engj.ulst.ac.uk http://www.

  9. RF/DC Sputter

  10. Pictures of the plasma ring

  11. Ref:L. C. Qin, D. Zhou,A. R. Krauss, D. M. Gruen, Appl. Phys. Lett. 72, 3437(1998)

  12. Microwave plasma system

  13. CH4 (methane) C2H2 C3H4 NH3 N2 Argon CO2 Ni Fe Co Source gas and catalyst

  14. Plasma enhanced CVD

  15. The AFM images shows the surface morphologies of Ni film that is coated by different kinds of RF power density. RF power density (a) 0.25W/cm2 (b) 0.5 W/cm2 (c) 1.0 W/cm2 Ref:Y. C. Choi, Y. M. Shin, Y.H. Lee, B.S. Lee Appl. Phys. Lett 76,2367(2000)

  16. The SEM images show the relation between the growth rate and the RF power density during the Ni sputtering process. Ref:Y. C. Choi, Y. M. Shin, Y.H. Lee, B.S. Lee Appl. Phys. Lett 76,2367(2000)

  17. Ref:Y. C. Choi, Y. M. Shin, Y.H. Lee, B.S. Lee Appl. Phys. Lett 76,2367(2000)

  18. Effect from the catalysts Fig.A-C SEM images of as-grown carbon nanotubes from catalyst A. nickel B.ion C. Cobalt. Ref: Z. P. Huang, D. Z. Wang,J. G. Wen, M. Sennett, H. Gibson, Z.F. Ren, Appl. Phys. A74,387-391(2002)

  19. Processes of vertically-aligned carbon nanotubes • Carbon is disassociated from the source gas (such as:CH4-CO2), and deposited toward the surface of Fe particle, where a physical absorption of carbon atoms occurs. • After carbon absorption, a saturated carbon film is formed from the continuous decomposition of source gas and it encapsulated the metal catalyst. • The catalyst and substrate surfaces were saturated with carbon layers, and Fe catalyst was pushed upward due to the diffusion and osmotic pressure. The wall of CNTs was formed and rolled up in spherical and cylinder shapes. • The CNTs in the lateral direction with multi-walled structure occur due to the additive precipitation of carbon species, with mutual reaction of hydrogen and oxygen, resulting in multi-walled CNTs. • Settlement of the deposited graphite on the inner tube walls induced by catalysts in the axial direction is graduated. Ref: M. Chen,C. M. Chen,H. S. Koo, C. F. Chen Diamond and related materials, 12(2003), 1829-1835

  20. Application • Flat panel displays • Vacuum microelectronics • Chargeable batteries • Field emission transistor

  21. Answer • 1.(a)MWPECVD can grow vertically aligned carbon nanotubes. (b) MWPECVD can grow carbon nanotubes at lower temperature. (c)Carbon nanotubes’ structures can be controlled through MWPECVD. • 2.Carbon nanotubes properties can be controlled by changing their structures ;moreover,their structures can be controlled through the size of catalyst.

  22. Reference • http:// www.applied-nanotech.com • http:// www.fundp.ac.be /~amayer/Gallery.html • http://www.engj.ulst.ac.uk • Ref:L. C. Qin, D. Zhou,A. R. Krauss, D. M. Gruen, Appl. Phys. Lett. 72, 3437(1998) • Ref:Y. C. Choi, Y. M. Shin, Y.H. Lee, B.S. Lee Appl. Phys. Lett 76,2367(2000) • Ref: Z. P. Huang, D. Z. Wang,J. G. Wen, M. Sennett, H. Gibson, Z.F. Ren, Appl. Phys. A74,387-391(2002) • Ref: M. Chen,C. M. Chen,H. S. Koo, C. F. Chen Diamond and related materials, 12(2003), 1829-1835

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