Emission of partial dislocations in silicon under nanoindentation

This paper investigates the critical loading condition that causes the emission of dislocations in silicon subjected to nanoindentation. A theoretical model is established, which follows the deformation process that with increasing the indentation load, a phase transformation takes place, followed by partial dislocations emitting from the interface between the phase-transformed zone and the originally crystalline silicon when the indentation load reaches a critical value. In the model, the emission process represents the generation of a dipole of Shockley partial dislocations. One partial dislocation of the dipole, located at the interface, is considered immobile, whereas the other partial dislocation moves into the bulk of silicon. The effects of the indenter geometry and of the location of dislocation nucleation on the critical indentation load are discussed. The model predicts that a sharp indenter leads to a relatively smaller critical indentation load. The model prediction is verified by an indentation experiment.