BLUESHIFT AND INTENSITY ENHANCEMENT IN VISIBLE EMISSION SPECTRUM OF C-AXIS ORIENTED SPRAY PYROLYTICALLY GROWN NANOCRYSTALLINE ZnO THIN FILMS

Abstract

Highly (002)-oriented nanocrystalline ZnO thin films were deposited on glass substrates at a substrate temperature of 500°C in air atmosphere by low-cost spray pyrolysis method. Room temperature photoluminescence spectral studies show the presence of near band edge emission and defect level emission (DLE) from the samples. The DLE wavelength is blueshifted about 22 nm and further emission intensity enhancement is observed in (002)-oriented sample as compared to that of wurtzite ZnO phase. The modifications in local defect levels and change in crystalline symmetry are attributed to the blue shift in the DLE region of c-axis oriented sample. The increased emission intensity of (002)-oriented samples is due to improvement in crystalline quality, preferential oriented growth and spherical morphology of nanocrystalline grains.