Deposition of hydrogenated amorphous carbon films from CH4/Ar plasmas: Ar dilution effects

Hydrogenated amorphous carbon (a-C :H) films were deposited, at room temperature, from a CH4/Ar plasma produced by a radio frequency (r.f.) glow discharge system at 13.56 MHz, and different power values. Two different characterisation techniques, Raman and FTIR spectroscopies, have been used to investigate correlations between deposition conditions and properties of hydrogenated amorphous carbon films. The composition of the initial gaseous mixture and the r.f. power input are shown to affect significantly both mechanical and microstructural properties of deposited films. As the fraction of argon in the feed gas is increased, the deposition rate increases and the deposited film shows a higher friction coefficient, thus suggesting the production of a softer material. On the other hand, Raman measurements suggest the occurrence of a lower degree of structural order in the sp2 lattice. Experimental findings are discussed in terms of the different chemical composition of the plasma.