Analysis of grain boundary dislocations by large angle convergent beam electron diffraction

Large angle convergent beam electron diffraction (LACBED) is used to analyse secondary dislocations in Σ3 and Σ9 grain boundaries in silicon. By selecting reflections from crystal planes common to the adjoining grans, LACBED images are insensitive to the boundaries except where dislocations are present. The dislocation images are closely similar to those for dislocations in single crystals and can be analysed by standard Cherns-Preston rules. It is shown that, for both boundaries, sufficient common reflections can be selected for a complete analysis, and that dislocations can be analysed assuming integer values of g · b, implying that the Burgers vectors are Displacement Shift Complete (DSC) lattice vectors. For both Σ3 and Σ9 boundaries, DSC dislocations are identified which are specific to these boundaries. The experimental conditions for the analysis of grain boundaries are explained, and the extension of the method to other coincidence boundaries is discussed.