Combustion CVD of diamond: Gas phase diagnostics and mechanistic studies

With the aim of providing a more detailed understanding of the reaction mec hanism in the combustion chemical vapor deposition (CVD) of diamond, two fl ame CVD systems were investigated. In an acetylene-oxygen flame at ambient pressure, the influences of important deposition parameters including stoic hiometry, substrate temperature and pretreatment as well as the effect of g as phase additives were studied systematically, and conditions for controll ed diamond growth were defined. From a large number of deposition experimen ts, film and growth properties such as growth rate, morphology, stress and purity were thus linked to the global gas phase composition. In a low-press ure CVD flame, gas phase constituents including important intermediates wer e analyzed in situ under selected deposition conditions to provide further insight into the reaction mechanism. For this, a combination of molecular b eam sampling mass spectrometry (MBMS) and laser spectroscopy was employed. The species profiles obtained from these experiments were compared with sim ulation results of the flame chemistry.