The structure and tribological properties of aluminum/carbon nanocomposite thin films synthesized by reactive magnetron sputtering

Hydrogenated nanocomposite aluminum/carbon thin films (Al/a-C : H) were fabricated on stainless steel and silicon wafer substrates via unbalanced reactive magnetron sputtering from an Al target in CH4/Ar plasma. The composition and structure of Al/a-C : H films were investigated by high-resolution transmission electron microscope (HRTEM), XPS and micro-Raman spectroscopy. Nanoindenter, interferometer and ball-on-disc tribometer were carried out to evaluate the hardness, internal stress and tribological properties of Al/a-C : H films. HRTEM observations confirmed that the metallic Al nanocrystallites were uniformly dispersed in the amorphous carbon matrix. XPS and Raman analyses indicated that the sp(2) content increased with the increase of Al content in the films. Nanoindenter and interferometer tests exhibited that the uniform incorporation of Al nanocrystallites can diminish drastically the magnitude of internal stress with maintaining the higher hardness of as-deposited films. Especially, the ball-on-disc tribometer measurements revealed that the nanocomposite film with 2.3 at.% Al content exhibited relatively better wear resistance and self-lubrication performance with a friction coefficient of 0.06 and wear rate of 3.1 x 10(-16) m(3)/N . m under ambient air, which can be attributed to the relatively higher hardness, the formation of continuous graphitized transfer film on counterface and the reduced reaction of oxygen with carbon. Copyright (C) 2010 John Wiley & Sons, Ltd.