Sp3 content in ta-C films vs pulse bias width to the substrate: A correlative structural analysis

Tetrahedral amorphous carbon (ta-C) films were studied with and without applying fixed pulse bias and frequency at variable pulse widths in double bent Filtered Cathodic Vacuum Arc (FCVA) system. Both from Raman and X-ray photoelectron spectroscopy (XPS) analyses it has been observed that the ratio of sp3/sp2 is maximal at pulse width of 15 µs with fixed pulse bias 3 kV and frequency 200 Hz. Increasing or decreasing pulse width from this threshold value accompanies the decreasing sp3 content in the film. It is also observed that with applying pulse bias width at said frequency and bias voltage G peak position was shifted to lower values and after reaching a minimum at 15 µs G peak position shifted to higher wave numbers. At the 15 µs pulse width, 3 kV bias voltage and 200 Hz frequency we have formed ta-C films with maximum sp3 content. This study clearly suggests that it is possible to tune the ta-C film's most important properties such as percentage of sp3 content, internal stress, and hardness by applying pulse width at particular frequency and bias voltage.