IN-SITU OBSERVED TWIN FORMATION ON ZNSE CRYSTALS GROWING BY SUBLIMATION

ZnSe crystals were grown by sublimation in closed ampoules between 133 5 K and 1365 K. The growth was observed in situ with a video camera af ter an abrupt change of the supersaturation. The crystals developed pr eferably {110} faces. Repeatedly a nucleus was formed in ortho-twin po sition on a small {111} face which truncated the corner of three adjac ent {110} faces. The repeated twin formation led to a preferred growth into the relevant <111> direction. The twinning already occurred at a low supercooling of less than 1 K and accelerated the growth distinct ly.