| The goals of this work were to synthesize ZnO and ZnO based alloys in the forms of thin films by using pulsed-laser deposition technique and to study the structural, stoichiometric, optical and electrical properties of these thin films for the potential applications in the new optoelectronic devices.; The optimized deposition conditions for growing epitaxial hexagonal MgZnO alloy thin films on sapphire (0001) substrates were determined by a systematic analysis of XRD and TEM. The epitaxial growth mechanism of these films on sapphire (0001) substrates is demonstrated to be domain-matched. The films are of high single-crystalline quality and show bright excitonic luminescence. Based on the RBS results, the maximum Mg concentration in the films with hexagonal wurtzite structure was found to be 34 at. %, which is almost ten times of the value allowed by the phase diagram. The bandgap energy of MgZnO thin films was found to be changed to the higher energy side with increasing Mg concentration. By changing Mg content, the bandgap of MgZnO alloy film can be tuned from 3.40 eV to 4.19 eV, this provides an excellent opportunity for bandgap engineering for optoelectronic applications.; For the potential applications in spintronic devices, epitaxial MnZnO thin films were also synthesized on sapphire (0001) substrates by using PLD. These MnZnO thin films have hexagonal wurtzite structure and very high single-crystalline quality according to the XRD, TEM and RBS results. The maximum Mn concentration was 35 at. %. The bandgap of these films shifts to the higher energy side with increasing Mn content. Magnetic investigations indicate that these films are paramagnetic.; Single-crystalline ZnO thin films have been grown successfully on Si(111) substrates by using PLD. This integration of ZnO thin films with silicon substrates was realized with two different heterostructures, ZnO/AlN/Si(111) and ZnO/MgO/TiN/Si(111). In ZnO/AlN/Si(111) heterostructure, the ZnO film was grown epitaxially on the AlN buffer which was grown on the Si substrate with domain-matching epitaxy. Two buffer layers were applied for the ZnO/MgO/TiN/Si(111) heterostructure. The excellent epitaxial property of TiN on Si substrate ensures the epitaxial growths of the MgO buffer layer and the ZnO film. These heterostructure thin films have excellent single crystalline quality and extremely bright excitonic emission based on the analysis of XRD, TEM and PL measurements.; An ultraviolet illumination-enhanced luminescence effect was observed in the ZnO thin film samples. We found that the PL intensity increased with the UV light exposure time. This new phenomenon is attributed to the oxygen desorption on the ZnO sample surface. A phenomenological model was proposed to explain this new effect. The time dependent equations derived from this model result in a very good agreement with the experimental data. (Abstract shortened by UMI.)... |
