Oxygen Partial Pressure Influenced Structural, Morphological and Optical Properties of Nanocrystalline ZnO Thin Films Formed by RF Magnetron Sputtering

Abstract

Zinc oxide (ZnO) thin films were deposited by RF magnetron sputtering on silicon (100) and glass substrates held at room temperature by varying the oxygen partial pressures in the range 5×10−3 Pa‐ 5×10−2 Pa.. The deposition rate of the films decreased from 5.8 to 2.5 nm/min with increase of oxygen partial pressure from 5×10−3 to 5×10−2 Pa. The content of oxygen in the films are correlated with the oxygen prevailed in the sputter chamber. The films formed at oxygen partial pressure 5×10−3 Pa showed (100), (002) and (110) reflections indicated the growth of polycrystalline ZnO films. Further increase of oxygen partial pressure to 2×10−2 Pa the intensity of (100) reflection increased and then decreased with increase of oxygen partial pressure to 5×10−2 Pa. The crystallite size of ZnO thin films increased from 15.0 nm to 21.8 nm and then decreased to 13.0 nm with increase of oxygen partial pressure from 5×10−3 to 5×10−2 Pa. The optical absorption band edge shifted towards lower wavelength side with increase of oxygen partial pressure, this indicates the optical band gap increased from 3.04 eV to 3.14 eV with increase of oxygen partial pressure.