| Zinc oxide is aⅡ-Ⅵwide band-gap (3.37eV) compound semiconductor with wurtzite crystal structure. This material has become an important topic in academic and industrial research, especially in the filed of electrical and optical devices because of its multi-functionality. ZnO is presently widely used in piezoelectric transducers, varistors, gas sensors, and transparent conducting films, which is important for the photovoltaic industry. Due to the large exciton binding energy of 60meV, it is regarded as one of the most promising materials for fabricating efficient ultraviolet (UV) and blue light emitting devices. ZnO has become another hotspot in the region of UV light emitting researching. ZnO has a potential to play an important role in the semiconductor field in future. With development of computer techniques and theory, computational materials are important contents in materials science recently. In this thesis, using a First principle theory based on Density-Functional Theory (DFT), we mainly investigated the things below:1. The atomic structures and electronic structures of ZnO low indexs surfaces and the surfaces adsorbed with transition elements were investigated with the methods of first principles, and get a lot of important data about ZnO surface. The main conclusions are the following:(1) Comparing the total energy of the several adsorption systems, we find that the most stable position of the transition elements is the "fcc-hollow" site for Zn-terminated surface and "on-top" site for O-terminated surface. The energy of surface with Ni adsorbed is most, but it is least when Zn adsorbed on the same site. (2) Surface state of ZnO (0001) decreases when transition elements adsorbed, and energy band structure of the surfaces more similar to which in bulk. Metallization of Zn-terminated surface will be strengthened when transition elements adsorption on. (3) The clean ZnO (1010) surface and Ti adsorbed ZnO (1010) surface are studied by first prineiples, It was shown that Zn atom move inside obviously after relaxation, which induced surface Zn-O dimer distorting. (4) The alteration of the charge density redistribution of the ZnO (1010) surfaee shows the electron transfer from surface layer to the adsobed Ti atoms, which leads to a metallization of the ZnO (1010) surfaee. (5) The electronic structure of ZnO (1120) close to which in bulk, and distribution of electric-charge density in region between Ni and O atoms is larger than that between Zn and O atoms, which lead to the metallization on this surface. 2. In this thesis, we present the atomic structures and electronic structures of Ni-ZnO contact, the results have shown that the Ni and Cr effect the electrical conduction of Ni-ZnO system when the Cr doping and Ni diffusion emerge in Ni-ZnO system.3. The [0001]/(1230)∑= 7 symmetric tilt boundary in ZnO are studied. It was shown that the Schottky barrier on pure grain boundary could not formed, but segregation of Fe is favorable to the forming of Schottky barrier.4. This work has shown that the layered ZnO varistor provides lower breakdown fields, lower leakage currents and higher non-linearity coefficients compared to varistors prepared by the conventional route. The improved current-voltage properties are attributed to a difference in the Fermi levels in the two layers which causes a variation in the electrical potential barrier height across the interface.5. The effect of transition elements doped in ZnO on electrical conduction is discussed, it was concluded that electronic property of ZnO is not only related with levels of electrons, but also associated with spin, spin-dependent scattering and spin-dependent hopping conductivity are maybe two important mechanics.
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