Fabrication And Properties Of Nonpolar ZnO Films And Nonpolar ZnO-Based Heteroiunctions

ZnO has a hexagonal wurtzite structure and usually grows along the polar c-axis that leads spontaneous polarizations effect which will greatly affect the luminous efficiency of LEDs and LDs. In order to hurdle this diversity, alternative growth orientations have been proposed with the polar direction within the growth plane. On the other hand, the production of high-quality, reproducible p-type ZnO remains a great challenge which hinders the development of ZnO-based homojunctions. Fabrications of ZnO heterostructures with native p-type materials have been considering as an alternative approach.In this thesis, we prepared LixNi1-xO thin films, nonpolar ZnO thin films, p-NiO(111)/n-ZnO(1120) heterojunctions and Mgo.2Ni0.8O/ZnO heterojunctions by pulsed laser deposition (PLD). The influence of growth parameters on the properties of LixNi1-xO films and the characteristics of p-NiO(111)/n-ZnO (1120) heterojunctions have been investigated. Besides, the energy band structure at the interface of Mg0.2Ni0.8O/ZnO has been studied.1. LixNi1-xO thin films were fabricated on the quartz substrates by PLD. The results indicate that the deposition pressure and growth temperature have significant influence on the properties of LixNi1-xO thin films. The LixNi1-xO thin film prepared at350℃under5Pa was revealed with the optimum properties.2. Reference to the experimental results of LixNi1-xO thin films prepared on quartz substrates, we prepared Two p-NiO(111)/n-ZnO(1120) heterojunctions with and without intermediate layer on r-plane sapphire substrates by PLD. It is revealed that by changing the deposition pressure of Li0.07Ni0.93O and with an MgZnO intercalation between NiO and ZnO layer, a heterojunctions with preferable characteristics was achieved.3. Based on our former work, MgNiO thin films with larger bandgap than NiO have been prepared. XPS determinations of the valence band offsets of the Mg0.2Ni0.8O(111)/ZnO(1120) and Mgo.2Nio.80(111)/ZnO(0002) heterostructures were performed, which show type-II band alignments at the interface for both heterostructures with VBOs of1.8±0.1eV and1.4±0.1eV (CBOs of2.4±0.1eV and2.0±0.1eV), respectively. The discrepancies of VBOs between the two heterostructures are mainly attributed to the ZnO orientation dependent spontaneous polarization effect.