Diamond nucleation on nickel substrates seeded with non-diamond carbon
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Oriented diamond films have been nucleated on single crystal nickel substrates seeded with non-diamond carbon and annealed at high temperatures in atomic hydrogen. The non-diamond carbon seeds included graphite powders, fullerene (60) powders, and gaseous carbon species. It was found that these different non-diamond carbon powders or species were effective in the enhancement of oriented nucleation of diamond. The morphologies of diamond films were similar regardless of the types of carbon used, suggesting a common nucleation mechanism involved. Based on the experimental observations, a revised model was developed for the oriented nucleation of diamond on Ni.
The heteroepitaxy of diamond films on Ni by chemical vapor deposition (CVD) has been the subject of intensive research both experimentally and theoretically.1"11 Sato et al. have reported oriented diamond nuclei formed on both (100) and (111) oriented Ni surfaces by microwave plasma CVD.4-5 The present authors have also demonstrated recently the oriented nucleation and growth of diamond on Ni by multi-step hot filament CVD.6"9 The process involves seeding the Ni surface with diamond powders, followed by high temperature annealing in atomic hydrogen. Diamond subsequently nucleates on such a seeded and annealed Ni surface with the same orientation as the underlying substrate, while the formation of graphite is inhibited. Tentative models for the nucleation of diamond on Ni substrate have been proposed.9 It is believed that the formation of certain surface intermediate states consisting of nickel, carbon, and hydrogen during the high temperature annealing process is critical for the successful nucleation and growth of oriented diamond films on the Ni substrates. Whereas previous research was limited to diamond seeds, this paper reports the use of non-diamond carbon powders and gaseous species as seeding materials on the Ni surfaces. The purposes of such experiments are (i) to expand the existing process parameters, (ii) to improve the nucleation density and orientation of the diamond films, and (iii) to test and refine the proposed nucleation models, thus furthering our understanding of the fundamental mechanisms involved. Non-diamond carbon powders of graphite and fullerenes (C6o) were used as seeds on the Ni substrates prior to the annealing and growth. In addition, gaseous carbon in hydrogen was also used to generate a "seeded surface" by saturating the Ni at high substrate temperatures prior to the growth. J. Mater. Res., Vol. 9, No. 5, May 1994
It will be shown that seeding and annealing with these different types of non-diamond carbon on the Ni surfaces was effective in the enhancement of oriented nucleation of diamond. The deposition experiments were carried out in a hot filament chemical vapor deposition system. Detailed descriptions of the growth system and the experimental procedures for the multi-step deposition process involving seeding, annealing, and nucleation have been given in earlier publications.6'7 Both (100) and (111) oriented Ni single crys
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