Investigation on physical properties and structure of amorphous hydrogenated carbon films

Hydrogenated amorphous carbon films were prepared by glow-discharge decomposition of pure CH4 at different gas pressure. Results of a study of optical and electrical properties and of the bonding and structure of the films are presented. The values of optical constants are close to those of dense hydrocarbons and nearly independent from gas pressure. Measurements of the temperature dependence of electrical conductivity indicate a conduction by extended states. The results of infrared spectroscopy indicate the existence of a hydrogen-rich phase with saturated groups. The films exhibit an electron spin resonance signal with g = 2.0027 ± 0.0001 and a line-width of 2.7 × 10-4 T without saturation effects. A density of states of 1020 - 1021 spin/cm3 is deduced.