Study of near white light emission for ZnO thin films grown on silicon substrates

ZnO thin films at growth time of 6, 8, 10 and 12 h were prepared by hydrothermal approach. The microstructure, surface morphology and photoluminescence properties were investigated by x-ray diffraction, field-emission scanning electron microscope and fluorescence spectrometer. The results reveal that all the thin films have hexagonal wurzite structure and preferential orientation along the c-axis. The density of nanorods increases first and then decreases with the increase of growth time. The photoluminescence spectra consist of sharp near band-edge, broad visible and near-infrared emissions. The chromaticity coordinates and color rendering indices of ZnO thin film at growth time of 10 h are x = 0.3537, y = 0.3744 and 90, respectively. The mechanisms of the green, yellow, orange-red, red and near-infrared emissions were discussed in detail.