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As-polished and homoepitaxial diamond (100)- and (111)-oriented single crystals, natural diamond powders of 0.12-6 μm diameter, and high-pressure/hightemperature (HPHT) diamond powders of 50-100 μm diameter were treated in a microwave hydrogen plasma under four sets of conditions. Negligible changes in the weights (±10 μg) of the as-polished and homoepitaxial diamonds were observed.Post-treatment atomic force microscopy (AFM) showed a combination of smoothing and pit formation on (100) surfaces, the details of which were sensitive to the structure of the starting surface. Asymmetric pits formed on an as-polished (111) surface, but no qualitative changes in the structure of highly defective (100) and (111) films were observed. Natural diamond powders, which were quite irregular and rough prior to treatment, became markedly smoother and well-faceted, as observed by scanning electron microscopy (SEM). The degree of faceting was sensitive to plasma power level but was independent of H2 flow rate. The size and degree of faceting appeared to be the same after plasma treatment for isolated and closelypacked particles; however, the latter fused into a quasi-continuous film. “Regrown” crystallites were observed on the surfaces of synthetic type Ib diamond particles following plasma treatment. We argue that surface diffusion is the dominant mechanism for the observed morphological changes.

Pu O'C reoDrt'i turoen for this collection of information is estimated to average 1 hour Per response. including the time for reviewing instructions. searching existing data sources. gatheri o antid -intaining the data needed, and completing and revie.ng the :ollec-ton of information Send comments regarding this burden estimate Or any other aspect of this Collecti of information, includong suggestions for reducing this ouraren to Washington Headduarters Services. )iDectorate for information Operations and Repofts, Approved for public release; distribution is unlimited. ABSTRACT (Maximum 200 words)A novel method for chemical vapor deposition and atomic layer epitaxy using radical precursors under medium vacuum conditions is being developed. Fluorine atoms are generated by thermal dissociation in a hot tube and abstract hydrogen atoms from precursor molecules injected immediately downstream of the source, generating radicals with complete chemical specificity.The radical precursors are then transported to the growing substrate surface under nearly collision-free conditions. To date we have grown diamond films from CC13 or CH 3 radicals together with atomic hydrogen, generated by injecting CHCI3 or C-4 and H2 into the F atom stream at reactor pressures between 10-4 and 10-2 Tort. This approach should be ideal for lowtemperature growth and atomic layer epitaxy: growth rates remain relatively high because activation energies for radical reactions are typically small and because the cycle times for atomic layer epitaxy can be reduced to the msec range by fast gas-stream switching, and cont tion and segregation are minimized by keeping the surface "capped' by chemisobe intermediates. ABSTRACT A novel method for chemical vapor deposition and atomic layer epitaxy using radical precursors under medium vacuum conditions is being developed. Fluorine atoms are generated by thermal dissociation in a hot tube and abstract hydrogen atoms from precursor molecules iajected immediately downstream of the source, generating radicals with complete chemical specificity. The radical precursors are then transported to the growing substrate surface under nearly collisionfree conditions. To date we have grown diamond films from CC1 3 or CH3 radicals together with atomic hydrogen, generated by injecting CHC1 3 or CM 4 and H2 into the F atom stream at reactor pressures between 10 -4 and 10-2 Torr. This approach should be ideal for low-temperature growth and atomic layer epitaxy: growth rates remain relatively high because activation energies for radical reactions are typically small and because the cycle times for atomic layer epitaxy can be reduced to the msec range by fast gas-stream switching, and contamination and segregation are minimized by keeping the surface "capped" by chemisorbed intermediates.