Comparative analysis of working gas composition impact on diamond films microstructure

Abstract

The paper report a diamond films with dendrite-like or nanofeathers structure. Such structures was synthesized both in CH4/H2 (12.2–19.3 vol.% CH4) and CH4/H2/N2 (7–18.5 vol.% N2) working gas mixture. The resulting diamond dendrites are composed of diamond crystallites of various sizes, as well as non-diamond carbon, with a height comparable to the film thickness and a lateral size does not exceed 200 nm (the minimum size of detected diamond crystallites is ∼ 5 nm). Such diamond structure seems cannot be classified to either conventionally nano- or ultrananocrystalline films. It is shown that nitrogen-rich diamond films have a larger size of both individual diamond crystallites and dendrites, as well as a higher level of residual stresses and roughness, compared to nitrogen-free diamond films. At the same time, nitrogen-free films have higher values of hardness and Young's modulus.