Effect of Two Different Thicknesses of ZnO Thin Films on the Photocatalytic Activities

Zinc oxide (ZnO) thin films with two different thicknesses (600 nm and 800 nm) were successfully deposited on to the glass substrates using a simple and inexpensive SILAR technique. The structural, optical and morphological properties of these films were characterized using X- ray diffraction, UV- vis spectrophotometer, PL spectroflurometer and scanning electron microscope, respectively. The X- ray diffraction analysis shows that the prepared film has polycrystalline nature and the crystallite grown predominantly along (002) plane of hexagonal wrutzite structure. The average transmittance of the films is found to be in the range of 55 - 75 % in the visible region. The optical transmittance and band gap are found to decrease for the film with 800 nm thicknesses. The scanning electron micrographs show that the grain size tends to decrease with increase of film thickness (800 nm). The decrease in PL emission of film of 800 nm could be the result of decreased rate of recombination of electron - hole. The photocatalytic activities of prepared films were investigated for the photodegradation of methylene blue under UV radiation and the photocatalytic efficiency is found to maximum (87.5 % for 80 min) for the film with 800 nm thicknesses.