【作者】 李强；

【导师】 刘保亭； 关丽；

【作者基本信息】 河北大学 ， 凝聚态物理， 2010， 硕士

【摘要】 本文采用第一性原理计算了六角纤维锌矿结构下的ZnO及掺杂ZnO的几何结构,电子结构和光学性质。采用第一性原理计算了六角纤维锌矿结构下的超晶胞ZnO(2×2×2)几何结构,能带结构,电子态密度及其光学性质。ZnO为直接带隙半导体,其带隙宽度为0.72 eV。其能带结构中的价带主要有三部分,是由O原子的电子和Zn原子的电子共同贡献的,而其导带主要是由Zn原子的电子贡献。由于O原子和Zn原子之间存在着光学跃迁,使得介电函数虚部出现三个主要峰,分别在1.59,6.49和10.25 eV处。另外,计算所得的ZnO吸收谱,反射谱,折射系数谱以及能量损失谱与实验值吻合的很好。采用第一性原理计算了掺杂Al,Ni和(Al,Ni)的ZnO的几何结构,电子结构和光学性质。在能带结构中,Al-ZnO的费米能级向上移动并进入导带内,形成n型半导体。Ni-ZnO和(Al,Ni)-ZnO由于Ni的掺入使得费米能级进入含有杂质能级的扩展导带内,形成n型半导体。纯ZnO,与Al-ZnO, Ni-ZnO和(Al,Ni)-ZnO的光学性质在低能处有较大的差异,但在高能处非常相似。At-ZnO在可见光区的吸收系数和反射率都非常低,反映其在可见光区有高透过率。相反,Ni-ZnO和(Al,Ni)-ZnO在可见光区的吸收系数和反射率都相对较高。另外,从光学吸收系数谱中可以清楚地看到,Al-ZnO的吸收边有蓝移的趋势,而Ni-ZnO, (Al,Ni)-ZnO的吸收边却是红移,并且Ni-ZnO和(Al,Ni)-ZnO的吸收跨度明显要比Al-ZnO的大。利用第一性原理研究了V族元素替位ZnO中的O原子以及P在ZnO中五种不同位置的掺杂,对掺杂前后晶体的能带结构、原子间电子重叠布局数,特别是光学性质进行了分析。计算结果表明：N、P、As、Sb替位O掺杂ZnO,其导电性为p型,P-ZnO和As-ZnO的电子结构相似。在五种不同位置的P掺杂ZnO中,只有PⅡ-ZnO为p型半导体,PⅢ-ZnO的系统总能最低,结构最为稳定。其光学性质在低能区也有较大的差异,但是在高能区差别较小。PⅢ-ZnO在低能区有较大的吸收系数和反射率,反映在可见光区有其低的透过率,而PⅠ-ZnO恰与之相反。更多还原

【Abstract】 The lattice structures, electronic structures and optical properties of pure ZnO and doped ZnO are calculated by first-principle study in this article.The calculated results including lattice structures, band structure, density of states and optical properties show that the supercell of ZnO (2x2x2). ZnO is a direct band gap semiconductor, and the band gap is about 0.72 eV.In the band structure, the valence band consists ofthree parts which are mainly formed of the electrons of O atoms and Zn atoms.For the conduction band, it is primarily derived from the electrons of Zn atoms.For imaginary part of the dielectric function, there are formed three peaks at 1.59,6.49 and 10.25 eV which are due to optical transitions between O and Zn.The optical absorption spectra, reflectivity spectra, refractive index spectra and loss function spectra which are fits very well with the experimental value.The lattice structures, electronic structures and optical properties of Al,Ni doped ZnO and (Al,Ni) codoped ZnO are calculated by first-principle study. For the band structures, Fermi level of Al moves up to the conductor band and formed the n-type semiconductor. Four impurity bands appear in band structure of Ni-ZnO and (Al,Ni)-ZnO, which exhibit n-type conductivity also.The results by calculation reveal that the optical properties of pure ZnO and Al-ZnO, Ni-ZnO, (Al,Ni)-ZnO have a large difference in the low energy range, but are similar in the high energy range.In the visible light range, the absorption coefficient and reflectivity of Al-ZnO are very small but a high transmissivity exists.On the contrary, the two parameters of Ni-ZnO and (Al,Ni)-ZnO are much larger than the other. Moreover, from the optical absorption spectra, it is clearly observed that the Al doped ZnO induces the blue-shift of the optical absorption edge, while Ni-ZnO, (Al,Ni)-ZnO induces the red-shift, and the absorption span of Ni-ZnO, (Al,Ni)-ZnO is bigger than Al-ZnO.The band structure, Mulliken charge overlap population and optical properties of V elements substitute for O site in ZnO structure and five-different-sites of P doped ZnO are calculated by the first-principle method based on density functional theory. In the sttucture of N, P, As, Sb doped ZnO, they are all p-type conductivity. The P-ZnO and As-ZnO have a similar electronic structure.In the five-different-sites of P doped ZnO, PⅡ-ZnO exhibits p-type conductivity. The final enthalpy of PⅢ-ZnO is lowest and the structure is the most stable one.The optical properties of five-different-sites of P doped ZnO are obviously different in the low energy range, while similar in the high energy range.In the low energy range, PⅢ-ZnO has the biggest absorption coefficient and reflectivity, which means a higher transmissivity in the visible light range.The results for PⅠ-ZnO are opposite to that of PⅢ-ZnO.更多还原