DLC films deposited by a neutral beam source: adhesion to biological implant metals

Hard carbon films have been deposited on implant-grade 316L stainless steel using a saddle source neutral beam system. The properties of the films in terms of hardness, intrinsic stress, adhesion and sp3 content have been investigated as a function of source current, system pressure and process gas mixture. It has been found that there is a strong correlation between the intrinsic stress and the sp3 content, as measured by Raman spectroscopy whereas there is little variation in hardness. The adhesion, as measured by the pull-off test is inversely proportional to the intrinsic stress. The source current has a significant effect on film stress and sp3 content.