Single crystal growth of LaCuOS by the flux method

Preparation of single crystals of LaCuOS, that is a transparent p-type semiconductor exhibiting violet-light emission, was demonstrated by the flux method using NaCl+KCl(1:1) as flux. The crystals were grown in an alumina tube inserted in an evacuated silica glass tube using the starting materials of La2O2S and Cu2S, as well as the flux and a small amount of K2S that reduces the coloration of crystals. Transparent colorless laminate crystals were obtained under the optimized crystal growth conditions; growth temperature 850 °C, growth time of 72 h and cooling rate 10 °C h−1. The size of the largest colorless crystal was 3.0×2.8×0.049 mm3. The crystal showed transmission as high as 60% and p-type electrical conductivity of 7.1×10−4 S cm−1 at room temperature.