Sulfur and Sodium: Diffusion of Potential Donors into Natural Diamond

The principal author reports here the main elements of work performed as part of his 1999 Ph.D. dissertation (Matthew Keith West, ''Diffusion of Sulfur into Natural Diamond: Characterization and Applications in Radiation Detection''. Ph.D. Dissertation, University of Missouri-Columbia, USA (1999)). In this study a Field Enhanced Diffusion with Optical Activation (FEDOA) reactor was constructed, tested, and employed to diffuse sulfur and sodium into polished, natural diamond plates. Various chemical sources of sulfur were used for diffusion from the gaseous, liquid, and solid phases. Diffusion coefficients in the range of 10 � 15 cm 2 /s to 10 � 14 cm 2 /s for temperatures 450-1050 � C, have been calculated for sulfur from concentration profiles determined from secondary ion mass spectroscopy (SIMS) analysis. Sulfur demonstrated n-type behavior with an activation energy of 0.9 eV. Sodium was found to diffuse into diamond with an average diffusion coefficient of 7.2 � 10 � 14 cm 2 /s at 750 � C. The different sources of sulfur provided qualitative information about competing mechanisms in the diffusion process.