Luminescence and photoconductivity studies on amorphous and nanocrystalline ZnO thin films obtained by sol-gel

Abstract

Amorphous and nanocrystalline ZnO thin films were synthesized by the sol-gel process at room temperature. The films were spin-coated on glass and silicon wafers and gelled in humid air. The ZnO films were synthesized by using zinc acetate dihydrate as the inorganic precursor. The samples were annealed at at 450°C for 15 minutes to produce a polycrystalline ZnO thin films. The films were characterized using X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy and transmission electronic microscopy and UV-Vis absorption spectroscopy. The experimental absorption spectrum of the crystalline ZnO film exhibits an absorption band located at 359 nm. Emission and excitation studies of the ZnO nanocrystallites were made in both kinds of materials to determine its luminescence response. Photoconductivity studies were performed on amorphous and crystalline (wurtzite phase) films. The experimental data were fitted with straight lines at darkness and under illumination at 355 nm and 633 nm. This indicates an ohmic behavior. Transport parameters were calculated. Results are discussed.