Physical properties of nanostructured ZnO thin films deposited by DC magnetron sputtering method with different volume of O2 in carrier gas

Abstract

High-quality ZnO thin films with polycrystalline hexagonal structure and (101) preferentially oriented were deposited on Si and corning glass substrates by reactive direct current magnetron sputtering. The effects of different oxygen concentration in carrier gas on structural, morphological and optical properties have been investigated. The increase of O2 concentration resulted in the decrease of preferred orientation intensity and peak shifting to lower 2? values. Scanning electron microscopic images showed a porous tapered columnar structure similar to the zone 1 of Thornton?s structure zone model at lower O2 content and a smooth microstructure similar to the zone T structure at highest O2 content. AFM images showed that film morphology and surface roughness were influenced by O2 concentration. UV-Vis-NIR measurements indicated that the UV absorption intensity of samples was increased and shifted to shorter wavelength (blue shift) at higher O2 concentration. Moreover, the optical band gap increased from 3.91 to 4.41 eV as a function of the oxygen concentration.