Microstructure, mechanical and tribological properties of graphite-like amorphous carbon films prepared by unbalanced magnetron sputtering

Graphite-like amorphous carbon (GLC) films were fabricated by unbalanced magnetron sputtering on silicon and stainless steel substrates. The effects of deposition bias voltage on the microstructure, mechanical and tribological properties of the resultant films were investigated by means of X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, atomic force microscopy (AFM), high resolution transmission electron microscopy (HRTEM), nano-indentation and tribological experiments, respectively. The results show that the present films are dominated by sp2 sites, and the microstructure and properties of the resultant films strongly depend upon the deposition bias voltage. Namely, the sp3 content, hardness, elastic modulus and critical load monotonically increase with increasing deposition bias voltage from 50 to 150 V, and then they decrease with further increasing the bias voltage to 185 V, while internal stress decreases at first and then increases with further increasing of deposition bias voltage. The films deposited at different bias voltages have high surface roughness. Tribological properties of the films are closely related with the deposition bias voltage, 150 V is the optimum value for obtaining good wear resistance.