Controlling the initial phase of PECVD growth of vertically aligned carbon nanofibers on TiN |
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Authors: | Farzan A. GhavaniniAuthor Vitae Maria Lopez-DamianAuthor VitaeDamon RafieianAuthor Vitae Krister SvenssonAuthor VitaePer LundgrenAuthor Vitae Peter EnokssonAuthor Vitae |
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Affiliation: | a Micro and Nanosystems Group, Department of Microtechnology and Nanoscience (MC2), Chalmers University of Technology, Göteborg, Sweden b Department of Physics and Electrical Engineering, Karlstad University, SE-651 88 Karlstad, Sweden |
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Abstract: | We explore the growth of vertically aligned carbon nanofibers by plasma enhanced chemical vapor deposition, using lithographically defined Ni catalyst seeds on TiN. TiN is selected for being an electrically conducting diffusion barrier suitable for the realization of electronic devices. We show that the rate of Ni diffusion correlates to both the level of oxygen content in the TiN film and to the film resistivity. The synthesis of the nanofibers was characterized using electron microscopy with an emphasis on three growth parameters: substrate temperature, plasma power, and chamber pressure. We propose that a catalyst surface free from carbon deposits throughout the process will induce diffusion-limited growth. The growth will shift towards a supply-limited process when the balance between acetylene, as the effective carbon bearing gas, and atomic hydrogen, as the main etching agent, is skewed in favor of acetylene. This determines whether the dominating growth mode will be vertically aligned ‘tip-type’ or disordered ‘base-type’, by affecting the competition between the formation of the first graphitic sheets on the catalyst surface and at the catalyst-substrate interface. |
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Keywords: | Vertically aligned carbon nanofiber VACNF TiN PECVD synthesis Growth mechanism |
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