SiO_x containing diamond like carbon (DLC) films have been deposited on silicon and stainless steel substrates under varying in fluence of RF self bias (−25 to −225 V) using a capacitively coupled RF generated plasma of argon (Ar), methane (CH₄) and hexamethyl disiloxane (HMDSO) gases. The deposited coatings have been char-acterized by load depth sensing nano indentation, spectroscopic elliposometry, X-ray photoelectron spectrosco-py, Fourier transform infra-red spectroscopy and Raman spectroscopy. Plasma has also been characterized by emissive probe and results indicate that impinging ion energy is mainly controlled by the self-bias values in this case. Characterization of deposited films indicate that sp³ bonded carbon content in the films is increasing with the RF self bias values on the substrates. A clear improvement in the optical, mechanical properties of the deposited films is seen with the increasing magnitude of RF self-bias. It is seen that with increasing magnitude of bias values, C content increases continuously in these films at the expanse of Si and O content and they finally got close towards ideal diamond like character beyond −150 V bias values.