ZnO nano-discs by lyophilization process: Size effects on their intrinsic luminescence

Abstract

Nano-discs of ZnO have been synthesized by a hybrid spray-freeze drying process (lyophilization), which allows a quasi-mono dispersity in size. Their marked shape anisotropy corroborates with a growth in the basal direction, parallel to the (0 0 0 1)-Zn and (0 0 0 1)-O polar surfaces. Their room temperature photoluminescence characteristics exhibit the standard shift of the spectral position of the ultraviolet intrinsic excitonic peak with an unexpected anomaly in terms of size effect on the excitonic peak's bandwidth. We observe that a small basal diameter of the ZnO nano-discs induced a red shift in the excitonic peak, with an anomalous narrowing of its bandwidth.