Systematic investigation on the deposition of thin silicon-carbon-nitride films by reactive rf magnetron sputtering from SiC-C composite target in nitrogen-argon atmosphere was studied. The significant effect of deposition pressures on the hardness of the deposited SiCN films was found, which varied between 4.7 and 44 GPa. The films were found to be amorphous from x-ray diffraction analysis but localized crystallization was noticed during atomic force microscopy (AFM) studies on these deposited films. The AFM studies also suggested that the increased hardness was due to reduction in particle size and localized formation of beta-C3N4 and beta-Si3N4 phase in the films. The x-ray photoelectron spectroscopy analyses showed the formation of C-N and Si-N bonds for the harder film. The increased nitrogen concentration in the sputtering gas mixture to 99% resulted in large particle growth and graphitic phase formation, which exhibited a low hardness value of 4.7 GPa. The high C content and low Si content in the deposited films facilitated the graphitic phase formation. (c) 2006 American Vacuum Society.