Monocrystalline silicon subjected to multi-asperity sliding: nano-wear mechanisms, subsurface damage and effect of asperity interaction

Nano-sliding between two surfaces often involves the interaction of many asperities. With the aid of molecular dynamics analysis, this study uses a three-asperity model to investigate the effects of the relative orientation and position of the asperities on the nano-wear mechanism of silicon. It was found that when the first asperity has created a damaged layer, the material would deform differently under subsequent sliding. A thin amorphous layer always remains and there is also an absence of dislocations when the depth of asperity penetration is small. On the other hand, when the asperities are not traversing a damaged zone, the forces experienced by the asperities are independent of their relative positions. The results suggest that the microstructural changes are localised and the initial sliding affects the subsequent deformation over a damaged region.