Fast, high-efficiency, and homogeneous room-temperature cathodoluminescence of ZnO scintillator thin films on sapphire

Excitonic luminescence in ZnO exhibits subnanosecond lifetimes combined with high efficiency, which makes epitaxial ZnO a promising ultrafast scintillator material for envisaged imaging applications with high data rate. ZnO thin films on sapphire show external ultraviolet electron-photon conversion efficiencies up to $0.42photons∕(keVe−)$ at room temperature and only minor lateral microscopic cathodoluminescence intensity variations. Peak shifts and occasionally observed double peaks found in cathodoluminescence spectra of epitaxial ZnO films with dependence on the detection geometry, the excitation depth, and the surface morphology are explained by a model based on photon propagation including self-absorption.