Deposition of dense hydrocarbon films from a nonbiased microwave plasma

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Abstract
An electron cyclotron resonance plasma was used to prepare C:H layers from methane. The temperature dependence of the deposition rate was investigated at substrate temperatures ranging from room temperature to 700 K, at a gas pressure of 1.6 Pa. Despite low ion energies corresponding to the plasma potential, transparent hard coatings were obtained at elevated temperature with a density up to 2 g cm−3. A deposition model is proposed which describes the growth from an adsorbed layer, including surface reactions with radicals and atomic hydrogen as well as the direct incorporation of ions. Two different deposition processes can be identified, yielding polymerlike films in the temperature range up to 450 K and dense hydrocarbons above this temperature. The observed temperature dependence of the film properties such as H/C ratio, index of refraction, and density is consistent with the predictions of the model.