Local luminescence of ZnO nanowire-covered surface: A cathodoluminescence microscopy study

Vertically aligned ZnO nanowires were synthesized on sapphire through vapor deposition using Au as a catalyst. In addition to the nanowires, the sample surface contained a thin wetting layer of ZnO clusters. Spatially and spectrally resolved cathodoluminescence (CL) microscopy was applied to correlate the luminescent properties and the sample structure. Local CL spectra and monochromatic images revealed that the nanowires are the major source for a strong and sharp I8 emission line, while two weak emissions at low energies originate exclusively from the wetting layer. Information on stress is also obtained from the relative position of the I8 line.