Stable low friction of sp2 nanocrystallited carbon films in different vacuum pressures

Abstract

This study reported the stable low friction of sp2 nanocrystallited carbon films in vacuum environment. Carbon film with larger sp2 nanocrystallites size demonstrated consistently low friction in different vacuum pressures. The lowest friction coefficient arrived 0.018 at 10–6 Pa with a long stable sliding cycles. The mechanisms were ascribed to the stable contact interfaces formed by the rapidly transferred sp2 nanocrystallites and the oxidation passivation layer. The low shear force at the nanocrystallited interface reduced the friction and the oxidation passivation promised the stabilization of interface. Carbon film with smaller sp2 nanocrystallite size only achieved low friction of 0.023 at 10–6 Pa, and the film exhibited high friction at 10-1∼10-3 Pa due to the insufficient passivation and large dangling bonds. As pure carbon film, sp2 nanocrystallited carbon films offer broadly application possibilities for vacuum micro-/nano- devices.