Effect of frequency and pulse width on the properties of ta:C films prepared by FCVA together with substrate pulse biasing

An investigation has been carried out to study the effect of frequency and pulse width on the deposition rate, intrinsic stress, morphological, micro-structural, mechanical and adhesive behaviour of tetrahedral amorphous carbon (ta:C) films prepared by a Filtered Cathodic Vacuum Arc (FCVA) system in conjunction with substrate pulse biasing. It is observed that the deposition rate increases with increasing frequency and pulse width in the lower ranges before it reaches to a more or less steady value of 25 nm/min at higher frequencies and pulse widths. The intrinsic stress in the film is reduced to a greater extent by the application of substrate pulse biasing. A stress reduction of approximately 85% can be easily obtained with an on-time (duty cycle) of 0.125%. The stress reduces further with increase in on-time, but at a slower rate. The morphological surface roughness increases with both frequency and pulse width. The micro-structural evaluation of the film using visible Raman spectroscopy shows that the intensity ratio of D-peak to G-peak (ID/IG) increases with increasing frequency. It is also observed that the G-peak width (FWHM) and the stress display a second order logarithmic correlation. The hardness shows a decrease in trend with increasing frequency. A noticeable increase in adhesion (critical load) with frequency is also observed in the lower ranges.