Effect of vacuum arc deposition parameters on the properties of amorphous carbon thin films

Abstract

Hard and smooth films of amorphous carbon with thicknesses in the nanometer to micrometer range were formed on silicon substrates using a vacuum arc deposition technique. In this technique, a carbon plasma is generated by a vacuum arc plasma source coupled with a magnetic filter for obtaining macroparticle-free amorphous carbon films. The influence of the substrate bias voltage and pulsed bias duty cycle on the film properties was investigated. A significant enhancement of the film quality and adhesion was achieved by applying a negative pulsed bias voltage to the substrate. Nanoindentation, pin-on-disk tribotesting, surface profilometry, Rutherford backscattering spectroscopy, elastic recoil spectroscopy, and Raman spectroscopy were used to characterize the properties and structure of the amorphous carbon films. It was found that the hardest films with the highest density and lowest friction coefficient were obtained at - 100 V pulsed bias voltage, whereas higher pulsed bias voltages improved the film adhesion and reduced the internal stress. For -100 V pulsed bias voltage, the maximum film hardness was achieved with a 50% duty cycle, and was significantly higher than that produced with a d.c. bias.