Influence of phosphine on the diamond growth mechanism: a molecular beam mass spectrometric investigation

We have used a molecular beam mass spectrometer to investigate the effects of addition of phosphine on the growth behaviour of diamond films in a hot filament chemical vapour deposition (CVD) reactor. Films were grown using gas mixtures of 1% CH4 with increasing amounts of PH3 (1000-5000 ppm). Gas phase species prevalent during the growth process (e.g. CH4, CH3, C2H2, PH3 and HCP) have been monitored quantitatively and compared with the corresponding growth rates, quality and properties of the resulting films. We find that addition of up to 2000 ppm PH3 increases the film growth rate by a factor of 2-3, and changes the crystal morphology in favour of(100). At higher PH3 concentrations (3000-5000 ppm) the growth rate decreases again, with predominantly (111) faceted crystals. These observations are discussed in terms of a model of the gas phase chemistry during the growth process. (C) 1998 Elsevier Science S.A. All rights reserved.