Inelastic deformation and phase transformation of shock compressed silicon single crystals

Silicon crystals were shock compressed along the [100] and [111] orientations to stresses between 15.9 and 21.7 GPa. Transmitted wave profiles exhibited considerable orientation dependence for elastic and inelastic waves but very little orientation dependence for the phase transformation wave. Following the phase transformation wave, the silicon was compressed similar to 23%. This compression is significantly greater than the previously reported compressions for silicon shocked to similar stresses, and the present data are consistent with a completed phase transformation. The measured mechanical impedance of the transformed silicon matches the bulk impedance of the simple hexagonal phase of silicon reported in static high pressure studies. (c) 2007 American Institute of Physics.