Deformation mechanisms of Σ = 9 bicrystals of silicon

Abstract

Interactions between dislocations and Σ = 9 grain boundaries were studied in slightly deformed silicon bicrystals by several imaging techniques. A very complex dislocation arrangement in the grains close to the grain boundary was revealed by TEM : pile-ups, networks with Lomer-Cottrell barriers, profuse cross-slip, local stress reversals. In situ observations by synchrotron X-ray topography suggest the possibility of dislocation transmission by Σ = 9 grain boundaries. Except for dislocations with the a/2 [011 Burgers vector, common to both grains, the reality of a direct transmission mechanism at the atomic scale was not confirmed by HREM investigations which proved that lattice dislocations dissociate in the grain boundary into DSC dislocations. These apparently contradictory results are discussed in terms of deformation conditions and core structures of dislocations.