UC Berkeley

Basic knowledge of the interfacial interactions, contact deformation, and structure changes in amorphous carbon (a-C) ultrathin films due to irreversible deformation is of critical importance to the protective effectiveness of these films. This paper presents a molecular dynamics (MD) analysis that reveals the role of surface passivation on the contact deformation and adhesion characteristics of ultrathin (<30 Å) a-C films possessing a layered structure consisting of intermixing, bulk, and surface layers. MD simulations reveal much higher interfacial adhesion, destabilization of the film structure resulting in partial sp3-to-sp2 rehybridization, and film delamination in the intermixing layer for unpassivated compared to hydrogen-passivated diamond surfaces. The results of this study illuminate the adhesion and contact deformation behaviors of ultrathin a-C films with layered structures, which are impossible to track experimentally due to the extremely small spatiotemporal scales.