Thermal analysis of hydrogenated amorphous carbon films prepared by plasma enhanced chemical vapour deposition

Hydrogenated amorphous carbon (a-C∶H) films were produced from propane and argon by an inductively coupled radio frequency (r.f.) glow discharge process under a particular deposition condition. Thermal analysis for the deposit by GC, DSC, DTA, and TG gave information for the structural changes upon heating. Most C-H vibration spectra disappeared by heating up to 600 °C. The gas desorption began above 300 °C and reached maxima above 650 °C with several peaks. The desorption reaction was endothermic. Up to 600 °C the desorbed gases was not the hydrogen. The large weight change was observed without the thickness reduction. The weight change rate was maximum at 480 °C. Hydrocarbons are believed to desorb below 600 °C. A hydrocarbon desorption model is suggested. Hydrocarbons are formed in the inner surface of a microvoid and effuse out through the interconnected microvoids in the column boundaries. The proposed desorption reaction is also endothermic.