GROWTH OF LARGE TETRAPOD-LIKE ZNO CRYSTALS .2. MORPHOLOGICAL CONSIDERATIONS ON GROWTH-MECHANISM

A newly developed method to grow large tetrapod-like ZnO crystals, described in part I, has made possible morphological observations of the products formed at each stage of the growth process. The octahedral nuclei are formed and grown in the oxide scales accompanying the generation of stresses and these crystals are expelled out of the grain boundary when they become unable to resist the internal stress. The emerged octahedral crystals begin to develop their alternative faces to form large and uniform tetrapod-like crystals in the vapor of zinc and oxygen. The octahedral nucleus as well as the accurate shape of the fourlings can be understood by supposing that at the initial stages of growth a nucleus was formed with cubic symmetry, corresponding to zinc-blende type ZnO.