Friction, wear, and triboelectron emission of hydrogenated amorphous carbon films

Amorphous and hydrogenated amorphous carbon films were prepared on a glass substrate using DC magnetron sputtering deposition in gas mixtures of H-2 and Ar having different H-2 content. Triboemission and friction were measured in a frictional system by sliding an Al2O3 ball across carbon films in a dry air atmosphere. Wear behavior of the carbon films was investigated by observing the worn surfaces with a scanning electron microscope (SEM) and an atomic force microscope (AFM). Carbon films prepared with low level H-2 gas contents showed low friction and low wear in the production of low electron emissions. With intermediate level H-2 gas contents, transitions of friction, wear intensity and electron emissions occurred from low to high. At high H-2 gas content, high friction and high wear occurred to produce high electron emissions. These wear mechanisms and the triboemission behavior are discussed in relation to the surface energy and internal compressive stress of the carbon film.