Quantifying the pressure-dependence of work of adhesion in silicon-diamond contacts

Abstract

Continuum mechanics models for contacting surfaces assume a constant interfacial energy, or work of adhesion, between materials. Recent studies have challenged this assumption, instead demonstrating that stress-dependent chemical reactions across the interface modify the work of adhesion. Here, we perform 77 adhesion tests on diamond-silicon contacts using in situ transmission electron microscopy and atomistic simulations to quantify how the adhesion changes as a function of applied pressure. The results show a sevenfold increase in the work of adhesion (from approximately 1 to 7 J/m2) with an increase in the mean applied pressure from 0 to 11 GPa, where the most significant increase occurs above 5 GPa. We rule out alternative explanations for the changing work of adhesion, such as electron-beam artifacts, bulk shape change by inelastic deformation, and time-dependent processes such as creep. Therefore, these results confirm the presence of stress-driven chemical reactions in the contact and quantify the resulting change in the adhesion of these materials with applied pressure.