Influence of Si on the Microstructure and Mechanical and Tribological Properties of Ag/a-C:H Films

The relatively high toughness, high adhesion to steel, and low internal stress of hydrogenated amorphous carbon (a-C:H) films containing Ag make them good candidate materials for various applications in sensors, tribology, and biomaterials; however, the relatively low hardness and poor tribological properties in oxidizing environments hinder their broad use. Incorporating a small amount of Si in Ag/a-C:H films may modify the film microstructure and, in turn, improve their mechanical and tribological properties. To test this hypothesis, Ag/Si/a-C:H films were synthesized by magnetron sputtering and their microstructure, composition, and mechanical/tribological properties were examined with various microanalysis techniques and mechanical testing methods. The Si content of the films was varied by controlling the rotational speed of the substrate. It is shown that the incorporation of Si in the films increases thesp(3)C,sp(3)CH, andsp(3)CH(2)contents, slightly roughens the film surface, and greatly improves the mechanical and tribological properties through the formation of a SiC phase. The results of this study also show that there is a critical Si content for optimal tribological properties.