Modulation of microstructure and optical properties of Mo-doped ZnO thin films by substrate temperature

Abstract

Mo-doped ZnO(MZO) films were deposited on Si (111) substrates by radio frequency sputtering at different substrate temperatures of 200, 300 and 400°C. The effect of the substrate temperature on the structural and optical properties of the MZO films has been investigated. X-ray diffraction results reveal that all the films are polycrystalline with a hexagonal wurtzite structure with a preferential orientation according to the direction (002) plane. The crystallinity and surface morphologies of the films are strongly dependent on the growth temperature, which in turn exerts a great effect on microstructural and optical properties of the MZO films. The optical absorption measurements show high ultraviolet (UV) absorbance property of MZO with sharp and intense absorption band in this region and the optical band gap (Eg) are 3.18, 3.22, 3.25 and 3.21eV for the films deposited at room temperature, 200, 300 and 400°C. The photoluminescence (PL) intensity of a strong broad violet–blue emission from MZO nanostructures with increasing deposited temperature was also observed. X-ray photoelectron spectroscopy (XPS) was employed to investigate the surface chemical composition of growth products.