Effects of negative bias on the structural, topological and tribological properties of amorphous carbon films prepared by magnetron sputtering

Amorphous carbon films were prepared in a magnetron sputtering system at different d.c. negative substrate biases(-50, -100, -150, -200 and -250 V). The surface roughness, hardness and tribological properties of as-deposited films were investigated based on the films' structural evolution. Compared with the films deposited at the negative bias of -50 and -250 V, the microstructure and bond configuration of the films deposited at negative bias of -150 V favored a more graphite-like structure, which had the maximum of graphiticclusters and ordering structures; meanwhile, the films deposited at bias of -150 V showed the minimum coefficient of friction (COF) in air, while the wear rate showed a decrease of two orders of magnitude. The tribotesting results were attributed to the increase of graphitic domains of amorphous carbon films which decreased the interfacial shear force and lowered the COF. The uniform and ordering structure induced steady and smooth friction curves. Copyright (C) 2010 John Wiley & Sons, Ltd.