Chemical Vapor Deposition of 12C Isotopically Enriched Polycrystalline Diamond

C-12 isotopically enriched polycrystalline diamond free-standing plates were synthesized by microwave plasma-assisted chemical vapor deposition. Diamond plates 30 mm in diameter and 100-600 mu m in thickness were successfully obtained at a typical growth rate of 3-5 mu m/h. The C-12 isotopic enrichment was 99.997%, whereas the nitrogen content was as low as 4 ppb. The preferential orientation of the (110) crystallographic direction normal to the substrate plane was proved using the X-ray diffraction pattern. The sharp Raman peak with a low background and a clear free-exciton recombination emission in a cathodoluminescence measurement at room temperature indicate that the polycrystalline diamond has a substantially high crystalline quality. (C) 2012 The Japan Society of Applied Physics