Fabrication of transparent very thin SiO_x doped diamond-like carbon films on a glass substrate

A novel direct current (DC) magnetron sputtering system via radio frequency (RF) bias with hexamethyldisiloxane (HMDSO) plasma polymerization was developed for the deposition of SiO_x-doped diamond-like carbon (DLC) films on a glass substrate. As the RF bias increased, the ratio of intensity of D peak and G peak (I(D)/I(G)) decreased and the G peak shifted to a low position, leading to high hardness and a large portion of sp³ bonds. Additionally, weak sp² graphite bonds were broken and sp³ diamond bonds formed because the RF bias attracted hydrogen ion bombarding the DLC films. Increasing DC power was helpful to improve the hardness of the DLC films because the proportion of sp³ bonds and the I(D)/I(G) ration was increased. HMDSO was introduced into this process to form SiO_x:DLC films with enhanced optical performance. The average transmittance in the visible region of these very thin SiO_x:DLC films with a thickness of 37.5 nm was 80.3% and the hardness of the SiO_x:DLC films was increased to 7.4 GPa, which was 23.3% higher than that of B270 substrates.