Localized cathodoluminescence of individual ZnSe nanorods

Highly oriented ZnSe nanorods were grown on a ZnSe epilayer on GaAs(001) substrate by metalorganic chemical vapour deposition without any introduced catalysts. Cathodoluminescence spectra and images of individual nanorods, projecting from the buffer layer, were obtained at various temperatures down to 4.5 K in a scanning electron microscope. They show that the luminescence of the nanorods is localized, with the near band edge and deep level related emissions originating predominantly from their interior and surface, respectively. The luminescence is also not uniform along the length of the nanorods. We attribute the strong surface luminescence to the post-growth oxidization of the nanorods when they were exposed in air. The temperature dependence of the cathodoluminescence spectra was also measured to study the energy gap of the nanorods, which was found to behave similarly to that of bulk ZnSe.