Large-area diamond deposition by microwave plasma

Diamond films of up to 1 mm thickness and of 30 cm(2) area have been grown in a 8 kW MW plasma reactor ASTeX PDS-19 using CH4/H-2/O-2 gas mixtures. Growth rate, film thickness radial profiles, diamond morphology and quality were evaluated in dependence substrate temperature (T=690-900 degrees C), and feed gas composition (CH4/H-2=2.5%, O/C=0-0.7). Translucent diamond wafers have been produced without ally sign of nondiamond carbon phases, Raman diamond peak being as narrow as 2.5 cm(-1). The presence of some impurities (N, H, Si and Al) was detected and analyzed with SIMS and IR optical absorption spectroscopy. An interesting type of diamond growth instability at certain deposition conditions is observed that manifests itself in the form of accelerated growth of selected diamond crystallites of very big lateral size (approximate to 1 mm), and of more perfect structure compared to the rest of the film. (C) 1997 Elsevier Science S.A.