Chemical erosion of graphite by hydrogen impact: A summary of the database relevant to diamond film growth

Abstract

It is now established that diamond can be grown by vapor deposition, a condition where graphite is the more thermodynamically stable state. This supposed contradiction of thermodynamics is explained by the recognition that hydrogen is more likely to chemically erode graphite than diamond. In most diamond growth environments, hydrogen gas must be kept above a certain concentration (>95% of the mixture) to deposit films with nearly no graphitic component. This paper discusses the chemical interactions of hydrogen with graphite. The discussion is primarily based on the database collected from studies in the fusion research community. The studies cover interactions using both energetic and low-energy atomic hydrogen. Kinetic models have also been developed which can explain reasonably well the observed interaction characteristics. The majority of the interaction studies used graphite as the target material for hydrogen; a few were also carried out with carbon and diamond films.