Next-generation hydrothermal ZnO crystals

Zinc oxide (ZnO) crystals were grown by the hydrothermal method under significantly improved conditions. Careful adjustment of critical growth conditions led the way towards ZnO crystals with extremely low (<1014 cm−3) lithium and potassium content. Photoluminescence reveals the low defect levels. The as-grown (0 0 0 1) surface exposes steps of 0.52 nm in height. High growth rates above 0.4 mm per day while observing narrow values for the X-ray rocking curve, FWHM from (0 0 2) reflection below 20 arcsec, and the growth of highly transparent, apparently colorless ZnO crystals are reported. Cautious co-doping with indium and lithium yields high-quality crystals.