Thermal stability of a-C:H:SiOx thin films in hydrogen atmosphere

Abstract

a-C:H:SiOx thin films were deposited by the plasma assisted chemical vapor deposition method, using polyphenylmethylsiloxane as a precursor. The thermal stability of a-C:H:SiOx films deposited on stainless steel substrates was investigated after thermal annealing of samples in a hydrogen atmosphere for 4 h at temperatures ranging from 300 to 700 °C. The sample analysis by optical and atomic force microscopy, nanoindentation, glow discharge optical emission spectrometry and Raman spectroscopy is reported here. Characterization of the mechanical properties of films (hardness, modulus, endurance capability, elastic recovery) was accomplished using the nanoindentation method. The investigation revealed that the above mechanical characteristics of a-C:H:SiOx films are very good up to 600 °C in hydrogen compared to un-doped diamond-like coatings. The hardness of the as-deposited a-C:H:SiOx films (11–13 GPa) showed no decrease after annealing at 600 °C. It is shown that the properties of films begin to change after annealing in hydrogen at a temperature of 200 °C more than during annealing in an air atmosphere. It is demonstrated that graphitization of a-C:H:SiOx films in hydrogen occurs at higher temperatures than in air.