中文摘要：

TiO2是一种新型的第三代半导体材料,具有重要的应用价值.Cu离子掺杂单晶金红石TiO2,可以改善TiO2对光谱的响应范围,提高转化效率.本文利用第一性原理分别研究了Cu离子填隙、Cu替代Ti、氧空位、钛空位以及含有复合缺陷时金红石TiO2结构及其相应光学性质的变化.结果表明,金红石的价带顶主要由O2p轨道贡献,导带底主要由Ti 3d轨道贡献;掺杂Cu离子后会在能隙中产生两条新的杂质能级;Ti空位使得晶体费米能量降低,在价带顶产生新能级;O空位使得费米能量升高,在导带底产生新能级,表现出n型半导体性质.通过对含有复合缺陷的晶体电子结构的分析,得到同时含有O空位和Cu填隙时对晶体在可见光范围的吸收影响最大.

英文摘要：

TiO2 is a versatile functional material in consumer products, such as fabrication of solar cells, light hydrolysis of hydrogen production and optical coating. Technologically, the absorption edge of TiO2 is in the ultraviolet（UV）region, which restrics its applications. Cu doping can solve the crucial problem and extend the absorption edge from the UV to the visible region. The first-principle calculation based on density functional theory with generalized gradient approximation and ultra-soft pseudo-potentials is carried out to investigate the defective rutile TiO2 through using the constructed 2×2×2 supercells in which all atoms are allowed to relax. The plane-wave cutoff energy is 340 e V by selecting2×2×3 of k-point in Brillouin zone. O vacancy, Ti vacancy, Cu interstitial, Cu substitutional for Ti and compound defects are all considered. After the structural relaxation, the lattice host is slightly distorted with a little change of the lattice parameters, with out affecting the crystalline phase of rutile. The results show that the valence bands are mostly O2 p states while the conduction bands have mainly Ti 3d properties. The defect of Cu interstitial can bring about two new impurity levels in the energy gap because of Cu 3d states, and the defect of Cu substituted for Ti can also induce two new impurity levels while they are next to the valence band due to the interaction between Cu 3d and nonbonding orbits of O 2p. Ti vacancy can cause the Fermi level energy to lower and produce a new impurity level at the top of the valence band, which will narrow the energy gap. O vacancy can enhance the Fermi level energy and produce a new level at the bottom of the conduction bands, which shows the n-type semiconductor properties. The higher the concentration of Cu substituted for Ti, the larger the band gap is. It is due to the strong interaction between Ti 3d and Cu 3d, which makes the conduction band move to higher energy. Different compound defects have different influences. Cu interstitial and O or Ti vac