Deformation of silicon – Insights from microcompression testing at 25–500 °C

The plastic deformation of silicon and other brittle materials near room temperature has conventionally been studied under high confining pressures, although it has been suggested that these may modify the dislocation core structure. Here, the possibility of using microcompression has been studied. Using this method the yield stress of silicon micropillars was measured for different pillar diameters and between 25 and 500 °C for a constant diameter of 2 μm. No pronounced effect of size on the yield stress was found, but the transition from failure by cracking to predominately plastic deformation was shown to be consistent with a previously proposed simple model for axial splitting. Deformed specimens were analysed by transmission electron microscopy to elucidate the operative dislocation mechanisms. This showed that at 500 °C deformation occurs by twinning and formation of partial dislocations, whereas at 100 °C it is associated with micro-cracking and only weakly dissociated dislocations.