Ultraviolet Super-Radiation Luminescence of Sputtering ZnO Film Under Cathode-Ray Excitation at Room Temperature

We report the observation of the cathode-ray (CR) pumped ultraviolet (UV) super-radiation luminescence in ZnO thin film at room temperature (RT). The dependence of UV (peak at about 390 nm) and green (peak at about 520 nm) luminescent peaks in ZnO thin film under CR excitation on excitation electron beam current has been investigated. With the increase of the density of excitation electron beam current, green peak relatively decreases and UV peak increases, resulting in a change of the luminescent color from green to blue-purple. The green peak intensity increases sublinearly with the increase of the electron beam current density and saturates at a relatively low density of electron beam current. But the intensity of 390 nm UV peak increases superlinearly with the increase of the electron beam current density. This is a UV super-radiation luminescence of exciton in ZnO under high density pump. In this paper, three-dimensional atomic force microscope images of the surface of unannealled and annealled ZnO films are given.