Electronic Structure and Electrical Properties of Mg-Substituted ZnO Oxide
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摘要: 采用密度泛函理论平面波超软赝势广义梯度近似方法，系统研究了Mg置换的ZnO基氧化物的晶格结构和电子结构，在此基础上分析了置换氧化物的电学性能。计算分析结果表明：Mg置换后的ZnO基氧化物其晶格减小，仍为直接带隙材料，带宽1.2 eV。Mg掺杂ZnO体系主要在-40 eV能量附近产生新的能带。费米能级附近的能带主要由Mg p、Zn p、Zn d、O p、Mg s、Zn s、O s电子形成，且这些能带之间存在着强相互作用。Zn p、Zn d、O p电子形成的能级上的载流子在外场作用下首先迁移至Mg s电子形成的能级，形成电输运过程。置换体系费米能级附近的载流子有效质量、态密度和载流子浓度都大大提高；Mg置换有利于ZnO材料体系电导率的提高。Abstract: The lattice structure, electronic sructure and electrical properies of the Mg doped ZnO have been systematically investigated by the ultro-soft pseudo-potentials based on the density functional theory calculations under the generallized gradient approximation.The calculational and analyzing results show the shrinked lattice and the increased direct band gap of 1.2 eV of the Mg doped ZnO system.There are newly formed bands near the -40 eV.The bands near Fermi level are composed by the Mgp, Zn p, Zn d, O p, Mg s, Zn s, O s electrons and strong hybridizations between them are found.The carriers of the bands formed by Zn p, Zn d, O p electrons hop to the bands formed by the s, and then the electrical conduction is accomplished.The carrier effective mass, density of states as well as the carrier concentration near Fermi level are increased for the Mg doped system.The electrical conductivity should be enhanced by Mg doping for ZnO.
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Key words:
- ZnO oxide /
- Mg doping /
- electronic structures /
- electrical properties
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图 1 计算采用的ZnO晶胞结构模型
Figure 1. ZnO cell structure model used in the calculation
(a) ZnO (b) MgZn7O8
图 3 计算所得ZnO和Mg置换ZnO的总态密度
Figure 3. Calculated total density of states
(a) ZnO (b) MgZn7O8
表 1 未置换ZnO和Mg置换ZnO基氧化物的晶格参数
Table 1. Lattice parameters for the un-doped ZnO and Mg doped ZnO
Compound a/(nm) b/(nm) c/(nm) ZnO 0.650 94 0.650 94 0.524 92 Mg doped ZnO 0.649 73 0.649 73 0.522 82 
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表 2 Mg置换ZnO的原子组成电子电荷分布
Table 2. Charge populations for elements of Mg doped ZnO
Element s p d Total charge O 1.85 4.99 0.00 -0.84e Zn 0.47 0.71 9.98 0.84e Element s p d Total charge O 1.85/1.88 5.01/5.10/5.11 0.00 -0.85e/0.86e/0.98e/0.99e Mg 0.37 5.73 0.00 1.90e Zn 0.47/0.49/0.50 0.69/0.77/0.78 9.97e 0.76e/0.78e/0.84e
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