Quality improvement of plasma-beam-deposited amorphous hydrogenated carbon with higher growth rate

An improved plasma beam deposition set-up, based on an expanding thermal plasma, is presented. Amorphous hydrogenated carbon films have been deposited on glass and crystalline silicon, under variation of the arc current and admixed acetylene flow. The films have been analysed ex situ with infrared absorption spectroscopy, broadband visible light transmission and nano-indentation measurements. These techniques reveal the growth rate, refractive index, bonded C - H density, optical bandgap and hardness. The growth rate and refractive index are found to increase with decreasing arc current and increasing acetylene flow admixture. The quality of the films in terms of refractive index and hardness increases with increasing growth rate and inverse energy coefficient, whereas the bonded hydrogen concentration and optical bandgap then decrease. From comparison of the growth rate dependency with the inverse energy coefficient dependency, we conclude that the growth rate is the preferred parameter in terms of which to describe the film properties because it is directly related to the plasma composition.