Structure and optical properties of ZnO nanowires coated with silica

It is essential to passivate one-dimensional nanostructures with insulating materials to protect them from contamination and oxidation as well as to avoid cross-talking between the building blocks of complex nanoscale circuits. The ZnO nanowires synthesised by the thermal evaporation of ZnO powders were coated with SiO2 by the sputtering technique. Transmission electron microscopy and X-ray diffraction analyses revealed that the cores and shells of the ZnO core-SiO2 shell nanowires were single crystal wurtzite type ZnO and amorphous SiO2 respectively. Photoluminescence measurements at room temperature showed that the passivation of the ZnO nanowires was successfully achieved with SiO2 without nearly degrading the near band edge emission from the wires. However, subsequent thermal annealing treatment was found to be undesirable owing to the degradation of the near band edge emission in intensity