Spatial Distribution of Defect Luminescence in ZnO Nanorods: An Investigation by Spectral Cathodoluminescence Imaging

Abstract

The spatial distribution of ubiquitous green luminescence (GL) in ZnO nanorods is investigated using cathodoluminescence (CL) spectral imaging. The vertically aligned, single‐crystal nanorods exhibit a strong GL emission at 2.42 eV at 80 K, attributable to oxygen vacancies. The spectral imaging reveals the GL emission is predominantly located in the surface layer of nanorods; the thickness and intensity of this layer decreases rapidly at elevated temperatures. On the other hand, the near‐band‐edge emission is weakest near the nanorod edges. The temperature‐dependent CL maps are consistent with the properties of a model in which singly ionized oxygen vacancies are stabilized by the surface band bending, which leads to the GL enhancement at the expense of near‐band‐edge emission. These results demonstrate the utility of spectral CL imaging to map the spatial distribution of defect luminescence in nanostructured materials.