Towards a general concept of diamond chemical vapour deposition

A C H O phase diagram is introduced providing a common scheme for all major diamond chemical vapour deposition (CVD) methods used to date. It reveals that low pressure diamond synthesis is only feasible within a well-defined field of the phase diagram, a diamond domain that allows general predictions of gas phase compositions and starting materials suitable for diamond synthesis. It gives an explanation for the quality variations of diamonds deposited from different gas mixtures. The concept originates from the thorough analysis of experiments by thermal CVD, hot filament CVD, various plasma deposition techniques and combustion flames. This analysis also shows that the large deposition rate differences between the various methods correlate well with the coirresponding gas temperatures, indicating that a hot spot in the gas phase fosters high rate diamond growth.