Sp 3 content in ta-C films vs pulse bias width to the substrate: A correlative structural analysis

Abstract

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 sp 3/sp 2 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 sp 3 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 sp 3 content. This study clearly suggests that it is possible to tune the ta-C film's most important properties such as percentage of sp 3 content, internal stress, and hardness by applying pulse width at particular frequency and bias voltage.