Bonding and hardness in nonhydrogenated carbon films with moderate sp3 content

Abstract

Amorphous carbon films with an sp3 content up to 25% and a negligible amount of hydrogen have been grown by evaporation of graphite with concurrent Ar + ion bombardment. The sp3 content is maximized for Ar + energies between 200 and 300 eV following a subplantation mechanism. Higher ion energies deteriorate the film due to sputtering and heating processes. The hardness of the films increases in the optimal assisting range from 8 to 18 GPa, and is explained by crosslinking of graphitic planes through sp3 connecting sites.