Investigation of growth modes of manganese mercury thiocyanate crystal by atomic force microscopy

The growth mechanism and defect formation of the {110} faces of manganese mercury thiocyanate crystals were investigated by atomic force microscopy. A dislocation-controlled mechanism and a two-dimensional nucleation mechanism operate simultaneously during growth. Previous observations showed that two-dimensional nuclei appeared at interstep terraces of spiral hillocks. In this work, it is found for the first time that layers of two-dimensional islands cover up the outcrops of screw dislocations. The spiral hillocks grow fast along the <114> directions, which is probably due to the small interplanar distances of the {114} faces. Two-dimensional islands often appear as pairs of islands of nearly the same size, at the larger step terraces. Crystallization of the liquid inclusions occurs during the separation of the sample from the mother solution. Small three-dimensional islands, in high density, induce extra stress, which subsequently generates after-growth dislocations.