One dimensional rod-shaped and two dimensional twin-crystal shaped ZnO crystals were fabricated by thermal evaporation of a mixture of ZnS and graphite powders in air at atmospheric pressure. Twin-crystal shaped ZnO crystals were formed at 1050°C, while rod-shaped ZnO crystals were synthesized at 1150°C. The morphology of ZnO crystals was drastically changed according to the growth temperature. It is particularly interesting that two hexagonal plates formed a twin crystal, in which hexagonal shaped ZnO plates were symmetrically grown on both sides of a mirror-like plane. The twin crystal looked like a yo-yo. X-ray diffraction analysis showed that the rod and twin-crystal shaped ZnO crystals exhibited a wurtzite crystallographic structure. A strong green emission peak at 500 nm was observed in the cathodoluminescence spectra of the ZnO crystals at room temperature.
2017 The Ceramic Society of Japan