Atomistic understanding toward the improved scratching properties of GaAs coated with monolayer graphene

Molecular dynamics simulation was performed to study the surface nanotribological behavior and subsurface damage of gallium arsenide (GaAs) substrate coated with monolayer graphene when subjected to the scratching action of diamond abrasive. Simulation result shows that the coefficient of friction and wear volume of GaAs/graphene surface are evidently lower than those of the bare GaAs surface for various scratching depths. The material removal of the graphene-coated GaAs workpiece is primarily attributed to compression- and shear-induced plastic deformation of GaAs, whereas abrasive wear is the dominant material-removal mechanism for bare GaAs workpiece. On the contrary, the GaAs workpiece coated with graphene exhibits severe subsurface damage due to the higher stress and that graphene can suppress the stress released within the GaAs workpiece during scratching; hence, the stress has to spread deeply. The scratching-induced slight deformation of graphene occurs when the scratching depth is higher than 15 Å. The deformed graphene induced by scratching is still capable of protecting GaAs substrate to some extent, but its C-C bond is vulnerable to be ruptured at the end of the scratching path due to a scratching-induced bulge structure. Increasing temperature can promote the scratching-induced surface wear and subsurface damage of GaAs workpiece. Monolayer graphene can improve the surface tribological properties of GaAs at each temperature. This work can provide atomic insights into the antifriction and antiwear design for GaAs when graphene is used as a coating.