The lifetime of non-equilibrium carriers in n-type unintentionally doped ZnO increases when the sample was exposed to the electron beam of a scanning electron microscope. This was observed by studying the ZnO cathodoluminescence spectra at different irradiation time durations and temperatures. It was found that the decrease in the cathodoluminescence spectra's peak intensity was related to a thermo-activated energy barrier, determined by the calculated activation energy value of 259meV. This energy value came close to the defect energy level of the zinc interstitial, which was possibly the nature of the energy barrier responsible for this decrease.

Cathodoluminescence Studies of Electron Irradiation Effects in n-Type ZnO. Schwarz, C., Lin, Y., Shathkin, M., Flitsiyan, E., Chernyak, L.: Journal of Physics - Condensed Matter, 2011, 23[33], 334204