Effect of bias voltage on Diamond-like carbon film deposited on PMMA substrate

Bilayered films composed of Diamond-like carbon (DLC) and silicon (Si) were prepared on the surface of polymethylmethacrylate (PMMA) substrates using plasma enhanced chemical vapor deposition (PECVD) and magnetron sputtering deposition. The deposited films were investigated by means of Atomic force microscopy, X-ray photoelectron spectroscopy and UV-Raman spectroscopy. Subsequently, the following mechanical and friction properties of the films were measured: The hardness by Nano-indenter, the friction coefficient and the wear rate by a ball-on-disk tribometer. After DLC film deposition, the higher hardness, lower friction coefficient and lower wear rate can be obtained for PMMA substrate. Results indicate that Chemical state, hardness and friction properties of DLC films on PMMA greatly depend on the negative bias voltage, applied on the substrate during the deposition. The friction coefficient values and the wear rate of DLC films are correlated to the hardness and sp3 content.