Large-scale fabrication of ZnO nanocrystals by a simple two-step evaporation-oxidation approach

Single crystal structures of ZnO nanocrystals were prepared on quartz and polyimide (PI) film substrates by using a thermal coater to promote thermal evaporation, followed by air circulation at 350 °C for 2 h to effect oxidation. HRTEM and TEM images show the individual ZnO nanocrystals have regular lattice order without stacking faults. After dispersion by an ultrasonic bath, ZnO deposited on PI film substrates can consist of individual and well-distributed nanocrystals with an average crystal size of 20-30 nm. In photoluminescence, the nanocrystalline ZnO exhibits strong UV emission at 395 nm, with no emission in the visible spectrum. The synthetic method described in this paper provides a simple and efficient method to fabricate ZnO nanocrystals on a large scale.