On the cyclic indentation behavior of crystalline silicon with a sharp tip

Detailed cyclic indentation experiments of crystalline silicon in this study show interesting behavior depending on the end phase from the previous cycle. To enable the behavior of these phases to be studied on reloading, the cyclic indentation response of the material is examined under conditions where the pressure-induced Si-II phase transforms either to amorphous (a-Si) or high pressure Si-XII/Si-III phases on unloading. For an amorphous end phase the subsequent reloading is hysteretic, and for high pressure crystalline end phases it is elastic. This indicates that, whereas a-Si re-transforms readily to Si-II upon reloading, Si-XII/Si-III does not retransform to Si-II even at the maximum indentation load. Based on the concept of the effective indenter shape and stresses induced in the material, we show that Si-XII/Si-III has a greater critical hydrostatic pressure for retransformation to Si-II than that of the diamond cubic Si-I.