Electrical, structural and optical properties of ZnO thin films grown by pulsed laser deposition

Abstract

We report the influence of oxygen partial pressure (PO2) on the electrical, structural and optical properties of no-stoichiometric ZnO (ZnO1-d) thin films grown by Nd:YAG pulsed laser deposition. We note that the electrical resistance of the ZnO1-d thin films is significantly modified by oxygen pressure; the electrical resistance decreases with the O2pressure in the range of 10 to 40 mTorr and reach a minimum resistance of r ~ 2.1x10-2W-cm at 30 mTorr increasing again after this pressure. These indicate that the increase/decrease of the electrical resistance is ascribed to the annihilation/formation of the residual donor-type defects in the ZnO1-d thin films, mainly due at the oxygen pressure. It is suggested that the decrease of the electrical resistance is due to the formation of oxygen vacancies (VO) complex defects. X-ray diffraction shown that the oxygen pressure doesn't affect the main peaks positions which reflect the existence of hexagonal ZnO single phase and five principal peaks (100), (002), (101), (110) and (103) appeared in the films. The ZnO1-d thin films shown an average transmittance of ~85% with optical band gap of average value of ~3.3 eV. Key words: Pulsed-laser deposition, zinc oxide, transparent conducting oxide, electro-optical properties.