Enhanced optical transmittance of spray deposited zinc oxide thin films for optoelectronic applications
Transparent zinc oxide thin films (undoped and Mo doped) were coated on glass substrates at the substrate temperature of 400°C using spray pyrolysis set up. The various Mo doping concentrations for the Mo doped thin films are 0.25wt.%, 0.5wt.%, 0.75wt.% and 1wt.%. Prepared thin films were characterized by X and UV-Vis Spectroscopy techniques. Thicknesses of the prepared films were determined using gravimetric method. XRD of the films shows that ZnO belongs to the hexagonal wurtzite structure. Preferred growth orientation for undoped and Mo doped ZnO thin films is along (002) direction, except for the 0.5wt.%Mo:ZnO thin film where the (101) peak becomes prominent. The XRD intensity of the (002) peak decreases with increasing Mo doping concentration for 0.25wt.% and 0.5wt.%, after which it increases for 0.75wt.% and 1wt.%. Crystallite sizes and lattice parameters for the ZnO and Mo:ZnO thin films were also evaluated. Optical studies of the prepared films show an average visible transmittance (AVT) of about 88% recorded in the 380nm to 800nm wavelength region. Optical bandgap for all the films were also reported. Slight increase in the bandgap of ZnO is observed with increasing Mo doping concentration.
Keywords: average visible transmittan optical bandgap.