Improving color rendering index of Mn-doped ZnO nanorods on silicon-based substrate

Porous silicon pillar array (PSPA) samples which are ideal substantial materials with dominant electronic and luminescence properties were prepared by surface etching method. ZnO nanorods with or without Mn doping grown uniformly and aligned onto PSPA regardless of lattice matching show various photoluminescence (PL) properties. The doped Mn ions in ZnO nanorods were directly observed by X-ray photoelectron spectroscopy (XPS), and ZnO structures were detected by X-ray diffraction (XRD). As the doping concentration increases, XRD peaks of ZnO nanorods shift to low angle. The influences of doping Mn ions on luminescence properties of ZnO nanorods were investigated. Except for the ultraviolet (UV) PL band, the broad PL band is observed at visible region. The band could be divided into three separate bands (orange, green and red) by Lorentzian deconvolution. The intensity of orange PL band firstly increases then decreases, and then gets the maximum at the doping Mn-to-Zn molar ratio of 2.0:100.0 which is the most effective doping concentration. The green PL band is attributed to zinc vacancy of ZnO, the orange PL band to Mn ions recombination of itself, and the red PL band to oxygen vacancy of ZnO, respectively. As the Mn-doped ZnO nanorods could emit yellow green luminescence excited by UV radiation, and doped Mn ions could improve the color rendering index of the luminescence, the nanorods could be used as promising white-light emitters in the future.