Published online by Cambridge University Press: 10 February 2011
The early stages of plasticity have been studied by nanoindentation at room temperature, with a new apparatus, in GaAs and MgO single crystals. On both materials a very well defined pop-in has been observed, whose characteristics depends on the initial dislocation density in the indented zone. On (100) cleaved surfaces of MgO crystals, several special surface features, including the presence of rosette arms, have been observed by SFM. Starting from these observations a dislocation mechanism has been proposed.