Influence of deposition conditions on mechanical properties of a-C:H:SiOx films prepared by plasma-assisted chemical vapor deposition method

A series of a-C:H:SiOx films was deposited on polished silicon and glass substrates by plasma-assisted chemical vapor deposition combined with pulsed bipolar substrate bias from mixtures of argon and polyphenylmethylsiloxane vapors. Different Ar pressures and substrate bias voltages were applied for the synthesis of a-C:H:SiOx films having different mechanical properties. Detailed characterization of the mechanical properties of a-C:H:SiOx films was made using the nanoindentation. Hardness and elastic modulus were used for the evaluation of the endurance capability (H/E) and resistance to plastic deformation (H3/E2). The structural properties of the deposited films were analyzed by Fourier transform infrared spectroscopy (FTIR) and Raman spectroscopy. It was shown that the Ar pressure and substrate bias variation can change the film properties and the growth rate and these changes are not linear. So, depending upon application, deposition conditions are to be optimized. In all of the examined coatings, increase of Ar pressure and amplitude of negative pulse of substrate bias lead to improvement in mechanical properties. According to the results of FTIR and Raman spectroscopy; this improvement is due to an increase in the sp3 bonded carbon content and decrease of hydrogen content in the films.