X-ray topographic investigation of characteristic dislocation structure in sapphire single crystals

The characteristic triangular cross-grid dislocation structure in sapphire single crystals has been investigated by means of x-ray transmission topography. Dislocations lay on (0001) basal planes and primarily appeared as three parallel groups of straight dislocation lines. At high temperature these dislocations can move easily on their slip planes and form different configurations by interacting and pinning. The analysis of Burgers vector and image width of dislocation lines confirmed that three parallel groups of straight dislocation lines are pure edge type having 〈112̄0〉-type Burgers vector, and a few dislocation reactions are the type of [112̄0]+[12̄10]+[2̄110]=0. The characteristic dislocation structure is closely related to the growth orientation.