Highly efficient cathodoluminescence from undoped ZnO nanophosphor

— Various ZnO morphologies with hexagonal cross sections were fabricated by using a thermal oxidation method. Comparison of the cathodoluminescence (CL) of synthesized ZnO to that of commercial ZnO:Zn phosphor revealed that strong green luminescence can be realized in undoped ZnO by using fabricated low-dimensional nanostructures. The reasons for the enhancement in CL intensity are investigated in detail. Reabsorbed UV emission by the nanostructures themselves could be partly converted into green emission and therefore contributes to the enhancement of green emission. Moreover, whispering gallery resonance modes produced in the hexagonal microcavity were assumed to provide one of the qualitative explanations for the observation of enhanced green emission.