Low-Temperature Wear of Silica Induced by Diamond Single Asperities

Atomic force microscopy is used to analyze the temperature dependence of nanoscale wear occurring during reciprocal line scanning of a SiO_{2} surface using diamond atomic force microscopy tips. Unexpectedly, our experiments show a wear rate that decreases with temperature. Thereby, the results cannot readily be reconciled with the common model of atomic scale wear, which assumes an abrasive process of thermally activated and shear-assisted atom-by-atom removal. Instead, shear-assisted tribochemical processes are taken into account. This is done based on a multibond model for single-asperity tribochemical wear as well as recent analysis of contact aging driven by bond formation for silica and diamond systems. We consider how thermally activated bond formation at different temperatures is met by temperature-dependent probabilities for bond rupture accompanied by wear. This allows us to rationalize the experimental results and link the temperature dependence of wear to the way an increasing number of interfacial bonds are ruptured at lower temperatures. Ultimately, our experiments thereby expand the emerging multibond model of single-asperity nanofriction and tribochemical wear to the temperature domain.