Structures and mechanical properties of diamond like carbon films prepared by closed-field unbalanced magnetron sputtering

Diamond like carbon (DLC) films were synthesized by closed-field unbalanced magnetron sputtering (CFUBM) using carbon targets in Ar and Ar/C2H2 atmosphere. The deposition rate, structure and mechanical properties of these films were studied as a function of applied bias voltage on the substrate during deposition. The film structures were investigated using Raman spectroscopy. The hardness and elastic modulus were measured by nano-indentation tests and the friction coefficient of DLC films was measured by a ball-on-disc type wear tester. Raman analysis showed that sp3/sp2 ratio in DLC films changed with increasing substrate bias voltage. Hydrogenated DLC films deposited at the bias of −200 V exhibited a maximum hardness of 28 GPa and a relatively low friction coefficient of about 0.1.