DIRECT EVIDENCE OF DISLOCATION TRANSMISSION THROUGH SIGMA=9 GRAIN-BOUNDARIES IN GERMANIUM AND SILICON BY INSITU HIGH-VOLTAGE ELECTRON-MICROSCOPY OBSERVATIONS

In situ straining experiments of Si and Ge bicrystals in the high-voltage electron microscope have clearly revealed that dislocations can be transmitted across ε = 9 coincidence tilt boundaries even when their Burgers vector is not a lattice vector of the second grain. Observed transmitted dislocations are either perfect dislocations with ½‘110’ Burgers vector or, more often, Shockley partial dislocations trailing behind them extended stacking faults linked to the grain boundary. Dissociation of dislocations into DSC dislocations glissile in the boundary was also observed. Observations of repeated transmission events at a given area of the grain boundary suggest that residual dislocations can be removed from the impact point. The main-but not all-observed features are explained by a simple model based on energy calculations of the possible dislocation configurations formed at successive steps of the transmission process. © 1990 Taylor & Francis Group, LLC.