光子学报, 2017, 46 (9): 0916004, 网络出版: 2017-10-16  

用GGA+U法研究稀土掺杂对ZnO电子结构磁性和光学性质的影响

GGA+U Study on the Effects of Electronic Structures, Magnetic and Optical Properties of ZnO Doped with Rare Earth
作者单位
1 西安理工大学 材料与工程学院, 西安 710048
2 宝鸡文理学院 物理与光电技术学院, 陕西 宝鸡 721016
3 西北工业大学 理学院, 西安 710072
摘要
基于自旋密度泛函理论框架下的广义梯度近似平面波模守恒赝势方法, 确定了准确计算Zn16O16超晶胞各原子对应的U值; 通过计算形成能和化学键的布局分析了掺杂结构的稳定性; 通过原子电荷布局和自旋电子态密度的计算分析了掺杂结构的能带结构和磁性状态; 讨论了各稀土原子掺杂对ZnO吸收光谱的影响. 结果表明: 稀土元素的引入使晶格膨胀, Zn-O键最长键增大而最小键减小, 导致氧四面体畸变; Y/La/Ce掺杂的ZnO具有亚铁磁性,Th掺杂ZnO则呈弱铁磁性, Ac掺杂ZnO为顺磁体; 稀土元素使ZnO的价带和导带下移, 费米能级进入导带, 增强了体系的电导率; Y/La/Ac掺杂对ZnO带隙宽度的影响较小, 吸收光谱略微蓝移, 而Ce /Th掺杂则有效提升了ZnO对可见光的吸收.
Abstract
Based on the rst-principles plane-wave norm conserving pseudopotential of the spin-polarized density functional theory(DFT), we determined the U value of each atom for the Zn16O16 supercell via the method of generalized gradient approximation(GGA+U). The stability of the mixed structure is analyzed by calculating the formation energy and chemical bond Population. The energy band structure and the magnetic state of each doped structure is analyzed by calculating the atomic charge Population and spin electronic state density. Finally The effects of each rare earth element on the absorption spectrum of ZnO are discussed. The calculated results show that the lattice is expanded by the introduction of rare earth elements, the longest Zn-O bond increases and the shortest Zn-O bond decreases, which leads to distortion of oxygen tetrahedron. Y/La/Ce doped ZnO possesses ferrimagnetism, Th doped ZnO exhibits weak ferromagnetism, and Ac doped ZnO is paramagnetic body. Rare earth elements make the valence band and conduction band of ZnO down, make Fermi energy level enter the conduction band, and meanwhile enhance the conductivity of the system. The effect of Y/La /Ca doping on the ZnO band-gap is small, and the absorption spectrum is slightly blue-shifted, while visible light absorption coefficient of ZnO is effectively improved because Ce/Th is doped.

杨志怀, 张云鹏, 许强, 张美光, 张蓉. 用GGA+U法研究稀土掺杂对ZnO电子结构磁性和光学性质的影响[J]. 光子学报, 2017, 46(9): 0916004. YANG Zhi-huai, ZHANGYun-peng, XU Qiang, ZHANG Mei-guang, ZHANG Rong. GGA+U Study on the Effects of Electronic Structures, Magnetic and Optical Properties of ZnO Doped with Rare Earth[J]. ACTA PHOTONICA SINICA, 2017, 46(9): 0916004.

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