Effects of Al incorporation on the mechanical and tribological properties of Ti-doped a-C:H films deposited by magnetron sputtering

Ti-and TiAl-doped a-C:H films were deposited on silicon substrates by magnetron sputtering Ti and TiAl target in argon and methane gas mixture atmosphere. To better elucidate the structural evolution after Al adding, X-ray diffraction, Raman spectroscopy, and X-ray photoelectron spectroscopy were used to comparatively analyze the structural transformation in the as-deposited films. Compared with Ti-doped a-C:H films, the introduction of Al enhanced carbon films graphitization effectively lowered the residual stress from 1.35 GPa to 0.65 GPa. Furthermore, though the hardness of TiAl-doped a-C:H films was moderately lowered, TiAl-doped a-C:H films exhibited higher toughness, lower friction coefficient and lower wear rate. The better tribological performances of TiAl-doped a-C:H films may originate from the formation of graphitized transfer layer during the friction test.