Elastic, plastic and cracking indentation behavior of silicon crystals

The ambient temperature indentation hardness properties of silicon crystals have been studied over the full range of their nanoscale elastic/plastic and microscale elastic/plastic/cracking behaviors. The material properties are interpreted on the basis of applied force versus residual indentation size or crack size measurements and, also, on the basis of computed hardness stress-strain dependencies. Cracking, when it occurs, is attributed to sessile dislocation reactions that are initiated at microslip system intersections. Significant hardening was revealed in nanoindentation tests of carbon-ion implanted material, particularly, for crack-free plastic deformation obtained when silicon carbide was formed in the crystal surface layer by high temperature implantation. Otherwise, continuous force vs. displacement curves were employed to track the occurrence of cracking during indenter loading and crack growth on unloading, as facilitated in the latter case by the residual plastic deformation produced during the loading part of the hardness cycle.