Growth mechanism and dynamic smoothening behavior of a-C:H:Si films for superlubricity

摘要

Tribological performances of materials significantly rely on the surface and interfacial properties such as chemical bonding state, rheological characteristics and surface roughness. Physically rough surfaces can probably cause high friction and severe wear in most sliding contacts. Ultrasmooth interfaces (i.e., atomic-scale profile roughness Ra) allow growing of pinhole-free films, which are definitely of high interest for producing low-friction or even friction-free lubricating materials. For instance, we have recently demonstrate that Si-containing hydrogenated amorphous carbon (a-C:H:Si) films grown from ion vapor deposition possess ultrasmooth surfaces (Ra～0.1 nm) and can display extremely low friction coefficient (～0.001) in dry N_2 [1,2]. However, the underlying growth mechanism of such an interface that is free of roughness remains unclear. In this work, we use dynamic scaling theory to characterize the evolution of roughness and correlate its effect to the structural properties of a-C:H:Si films.