In situ observation of twin formation during the growth of ZnSe single crystals from the vapor phase

Single crystals of ZnSe are grown by sublimation in closed ampoules of fused silica at temperatures between 1300 and 1400 K. With a video camera it is observed that the crystals develop preferably {1 1 0} faces. The free corner of three {1 1 0} faces appears as the preferred place of formation of a nucleus in twinned position. Repeated twin formation leads to a dominant growth in the [1 1 1] direction. Pn the presence of SiS2, however, {1 0 0} and {1 1 1} faces appear near equilibrium and twins form on {1 1 1} faces resulting in a preferred growth in [1 1 2] directions. These observations are qualitatively explained by an idealized atomic arrangement of growth steps. (C) 1999 Elsevier Science B.V. All rights reserved.