Physical Characteristics Of ZnO And ZnO-Based Diluted Magnetic Semiconductors Fabricated By PLD

The crystalline ZnO films have been deposited by the pulsed laser deposition (PLD). The relation between different deposition parameters and the structure properties of ZnO films is analyzed and the optimized condition is obtained. Based on those results, the films with Al, Ni, Mn doping in ZnO films have also been prepared and the influence of doping contents on properties of the films is studied. Furthermore, using a Nd:YAG laser as fundamental beam, the second-harmonic efficiency of the films is measured. The main results are as follows:ZnO thin films with highly c-axis orientation have been fabricated by PLD method. The influence of substrate temperature and oxygen pressure on the properties of the films is studied. The reason why the growth model of ZnO films changed with the deposition condition is explained. The room-temperature PL spectra of the ZnO films grown at different oxygen pressures have been investigated. All films show a typical luminescence behavior with a narrow ultraviolet (UV) and a broad green-yellow band. It is proposed that the intensity of UV emission depends on crystal structure and the deep level emission correlates to the electron transitions from the bottom of the conduction band to the antisite oxygen OZn.High quality Al doping ZnO transparent conductive films have been fabricated by mixing Al into ZnO target. The effect of doping concentration on their structure, electrical and optical properties is studied. The results show that the low electrical resistivity can be obtained under appropriate doping content and the optical direct band gap of films is dependent on the carrier concentration.High-quality Ni-, Mn-doped ZnO thin films have been deposited and obviously room-temperature ferromagnetic behavior is obtained. The effect of doping concentration on the ferromagnetism mechanism of Zn1-xNixO films is analyzed. The ferromagnetism of Zn1-xMnxO films is strongly related to the defects in ZnO films, but the correct doping concentration is crucial for obtaining room-temperature ferromagnetism.Using a Nd:YAG laser of 1064 nm as a fundamental beam, the second-harmonic efficiency of ZnO films have been discussed, showing that the second harmonic signal is generated not only inside crystallites, but also at grain boundaries. The increased of SHG intensity of Zn1-xMnxO films with highly doping concentration are explained by the existing of Mn cluster in the films. The declining ferromagnetism of Zn1-xMnxO films is identified.