Evidence of enhanced atomic hydrogen production with halogens in diamond MWPACVD

Abstract

Abstract Optical emission spectroscopy measurements and exhaust gas mass spectrometry were used for diagnostics in a microwave plasma assisted chemical vapor deposition reactor for diamond growth. An actinometry technique was used to study the atomic hydrogen generation with additions of CF4 and CCl2F2 in the feed gas. The relative emission intensity of the atomic hydrogen line Hα (656.3 nm) was measured with CF4 and CCl2F2 concentrations in the range of 0–5%. The results show an increase in atomic hydrogen concentration up to 80 and 200% when CF4 and CCl2F2 are added in the mixture, respectively. The -ideal actinometry conditions and the validity of the observed increase of atomic hydrogen with an change in electron temperature and density in the plasma was investigated. The dissociation process of CF4 and CCl2F2 associated with HF and HCl formation were discussed by measurements of stable species by mass spectrometry of the exhaust gas. The increase of the atomic hydrogen concentration is correlated with the easy HCl and/or HF dissociation by electron-impact.