Influence of oxygen flow rate on the morphology and the optical properties of thin ZnO films grown by pulsed laser deposition

ZnO is an interesting wide-band-gap semiconductor material with a direct band gap of 3.37 eV at room temperature and it makes more attention to the ultraviolet (UV) optoelectronic devices, such as UV laser, optical waveguide, and exciton-related devices. Usually, an insufficient supply of oxygen in ZnO during growth precludes various applications. In order to overcome these difficulties and obtain a strong ultraviolet near band edge emission and a much weaker emission band correlated with deep-level defects, it is necessary to prepare a high-quality thin ZnO film. In this paper, different oxygen flow rates (30, 50 and 70 sccm) are introduced into the vacuum chamber and the influence of oxygen flow rate to the thin film quality is studied. It can be seen that thin ZnO films with strong c-axis preferred orientation are grown on single crystal silicon (111) and quartz (SiO2) substrates by pulsed laser deposition (PLD) method. In the range of 30~70 sccm for oxygen flow rate, thin ZnO film fabricated under the condition of O2 flow rate of 50 sccm has higher optical transmittance above 80%, higher O2 content~ 40.71%, higher growth rate ~252 nm, stronger ultraviolet near band edge emission and a weaker emission band correlated with deep-level defects.