Dislocation controlled wear in single crystal silicon carbide

For better design and durability of nanoscale devices, it is important to understand deformation in small volumes and in particular how deformation mechanisms can be related to frictional response of an interface in the regime where plasticity is fully developed. Here, we show that when the size of the cutting tool is decreased to the nanometer dimensions, silicon carbide wears in a ductile manner by means of dislocation plasticity. We present different categories of dislocation activity observed for single asperity sliding on SiC as a function of depth of cut and for different sliding directions. For low dislocation density, plastic contribution to frictional energy dissipation is shown to be due to glide of individual dislocations. For high dislocation densities, we present an analytical model to relate shear strength of the sliding interface to subsurface dislocation density. Furthermore, it is shown that a transition from plowing to cutting occurs as function of depth of cut and this transition can be well described by a macroscopic geometry-based model for wear transition.