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MATERIALS RESEARCH

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Coalesced oriented diamond films on nickel P. C. Yang, C. A. Wolden, W. Liu, R. Schlesser, and R. F. Davis Department of Materials Science and Engineering, NCSU, Raleigh, North Carolina 27695-7919

J. T. Prater Army Research Office, RTP, North Carolina 27709

Z. Sitar Department of Materials Science and Engineering, NCSU, Raleigh, North Carolina 27695-7919 (Received 19 May 1997; accepted 15 December 1997)

The growth of coalesced, highly oriented diamond films has been achieved on nickel substrates using a multistep process that consisted of (i) seeding the Ni surface with 0.5 mm diamond powder, (ii) annealing at 1100 ±C in a hydrogen atmosphere, and (iii) growth at 900 ±C in a mixture of hydrogen and 0.5% methane. Auger depth profile analysis of a sample quenched after the annealing stage showed the presence of significant amounts of carbon (6 at. %) close to the substrate surface and about 3 at. % deeper in the substrate. The loss of carbon into the substrate resulted in relatively low nucleation density. The addition of methane into the gas phase during the annealing stage proved very effective in compensating for the diffusion. An addition of 0.5% methane in the gas phase produced optimum results, as the nucleation density, orientation of diamond particles, and uniformity were substantially improved. Substrates nucleated under these conditions were grown out into coalesced, 30 mm thick films. Both (100) and (111) oriented films showed a high degree of orientation and Raman spectra obtained from these orientations showed intense and narrow diamond signature peaks with FWHM’s of 5 and 8 cm21 , respectively.

Nucleation and growth of coalesced, oriented diamond films on non-diamond substrates is important for many applications. Transition metals, and nickel in particular, are attractive substrates for the heteroepitaxial growth of single crystalline diamond films because of their close lattice match to diamond and their catalytic properties.1 Dewan and co-workers2 reported on precipitation of diamond particles from different mixtures of diamond and metal powders. Tachibana et al.3 achieved near heteroepitaxial growth of diamond on (111) platinum. We have observed that under certain conditions and in the presence of atomic hydrogen oriented diamond nuclei form from a supersaturated Ni–C–H surface solution.4 Following this initial success, we developed a multistep growth process and achieved reproducible heteroepitaxial nucleation of diamond on Ni substrates.5 Despite producing oriented and well-faceted diamond nuclei on Ni, the nucleation density was rather low and nonuniform across the substrate. This limitation has prevented the production of continuous, oriented diamond films. In this communication we report on the improvement of the nucleation density and uniformity through methane enrichment during the annealing stage of the process. These advances allowed the first production of coalesced, oriented diamond films on nickel substrates. 1120

J. Mater. Res., Vol. 13,