Improved reproducibility in zinc oxide single crystal growth using chemical vapor transport

The crystal growth process of zinc oxide (ZnO) by chemical vapor transport (CVT) using carbon as the transport agent is developed. The comparison between the chemical reaction rate and the diffusion velocity is our primary point of view. In ordinary CVT systems, the transport rate is diffusion-limited because the chemical reactions of both source and growth sides reach an equilibrium extremely faster than the diffusion velocity. Nevertheless, in our system, the transport rate is kinetics-limited because the estimated chemical reaction rates are slower than the diffusion velocity. Configurations of ampoules have been devised to decrease the diffusion velocity and to change from the kinetics-limited transport to the diffusion-limited one. Then the reproducibility of ZnO single crystal growth was considerably improved.