Structural and optical properties of diamond like thin films deposited by asymmetric bipolar pulsed-DC reactive magnetron sputtering

In contrast with PECVD technology, reactive sputtering of graphite allows an independent control of the substrate bias. This characteristic permits the modification of film properties without varying the plasma composition. In the present study, the characteristics of DLC films grown by pulsed-DC reactive sputtering were determined as a function of substrate bias. Asymmetric bipolar pulsed-DC in a gas mixture of Ar and 7.5% CH4 with substrate bias in the range of − 300 V to 0 V, provided wear resistant a-C:H films with wear rate values in the range of 15 to 23 · 10− 15 m3 m− 1 N− 1. DLC exhibit characteristics associated to hydrogenated DLC films (DLCH), namely: moderate sp3 content and mass density (up to 1.8 g/cm3), low hydrogen content (∼ 30%) and high transparency (> 90%) up to wavelengths of 700 nm with a Tauc gap energy up to 1.9 eV. Moreover, they also showed low stress values and moderate wear rates, as shown in previous studies.