A molecular dynamics analysis of the effect of surface passivation on the adhesion, deformation behavior and structure stability of amorphous carbon ultrathin films

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 angstrom) 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 sp(3)-to-sp(2) 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. (C) 2021 Elsevier B.V. All rights reserved.