Investigations of the gas phase mechanism of diamond deposition in combustion CVD

Two diamond combustion CVD systems have been investigated with respect to t he reaction mechanism in the gas phase: an atmospheric acetylene-oxygen wel ding torch and a flat, premixed acetylene-oxygen-argon flame at 50 mbar. Th e atmospheric pressure flame was used to study the influence of important d eposition parameters including stoichiometry, deposition time, substrate te mperature and pretreatment as well as that of some chemical additives. In t he low-pressure flame, the chemical composition in the gas phase was invest igated in detail for some specific deposition conditions. A combination of laser techniques and molecular beam mass spectrometry was used to measure s patially-resolved temperature and species concentrations with and without a substrate present. The results for some stable and intermediate species ar e compared with recent numerical models of the gas phase chemistry. An over view is given of some recent experiments, and perspectives for further work an discussed. (C) 2000 Elsevier Science S.A. All rights reserved.