Dislocations at spinel surfaces

The structure of evaporation patterns created by stationary and moving dislocations which terminate on the (0 0 1) surface of MgAl2O4 is discussed. When the Burgers vectors of the dislocations are inclined with respect to the (0 0 1) crystal plane, these dislocations create evaporation patterns in the form of double spirals. The double evaporation spirals develop through the synergistic rotation of pairs of 2-إ-high half-ledges originating at the dislocation termination points. The dislocations, whose Burgers vectors lie in the (0 0 1) crystal plane, do not form spirals when terminating on the (0 0 1) surface, but may create kinks in the surface steps. The presence of the dislocation-related kinks causes local cusping of the surface steps.