ELASTIC, PLASTIC AND CRACKING INDENTATION BEHAVIOR OF SILICON-CRYSTALS

The ambient temperature indentation hardness properties of silicon cry stals have been studied over the full range of their nanoscale elastic /plastic and microscale elastic/plastic/cracking behaviors. The materi al properties are interpreted on the basis of applied force versus res idual indentation size or crack size measurements and, also, on the ba sis of computed hardness stress-strain dependencies. Cracking, when it occurs, is attributed to sessile dislocation reactions that are initi ated at microslip system intersections. Significant hardening was reve aled in nanoindentation tests of carbon-ion implanted material, partic ularly, for crack-free plastic deformation obtained when silicon carbi de was formed in the crystal surface layer by high temperature implant ation. Otherwise, continuous force vs. displacement curves were employ ed to track the occurrence of cracking during indenter loading and cra ck growth on unloading, as facilitated in the latter case by the resid ual plastic deformation produced during the loading part of the hardne ss cycle.