物理学报2017，Vol.66Issue(13)：233-241,9.DOI:10.7498/aps.66.137101
GGA+U方法研究ZnO孪晶界对VZn-NO-H复合体对p型导电性的影响
Effect of ZnO twin grain boundary on p-type conductivity of VZn-NO-H complex: a GGA+U study
摘要
Abstract
Theoriginofthep-typeconductivityinN-dopedZnO hasbeenacontroversialissue foryears,sinceisolatedN substituted for O site (NO) was found to have high ionization energy. A recent experiment demonstrates that the p-type conductivity is attributed to the VZn-NO-H shallow acceptor complex. However, besides the complex, there are many other defects in ZnO, such as twin grain boundaries. They are commonly two-dimensional defects, and inevitably affect the p-type conductivity of the complex. By applying first principle calculations, we present the electronic structures and p-type conductivity of ZnO Σ7 (12-30) twin grain boundaries containing VZn-NO-H complexes. Four types of Σ7 twin grain boundaries are investigated, and the VZn-NO-H complex is found to have a tendency to appearing in the stress raisers of the twin grain boundaries. The lowest formation energy under Zn-rich condition is only 0.52 eV for the complex in GB7a, a type of Σ7 twin grain boundary with anion-anion bonds, while the value is 3.25 eV for the complex in bulk ZnO. For the ionization energy, the complex in GB7a is more easily ionized, and has a value of 0.38 eV, compared with 0.67 eV in bulk ZnO. The result of density of states shows that the electron transition is dominated by the empty defect levels in forbidden band, which are occupied by O 2p and N 2p orbital. Further analysis indicates that the special structure of GB7a shortens the distances between NO and its neighbor O atoms, and the shortest N—O bond isonly2.38?,whichalsomeansastrongorbitalhybridizationbetweenOandN.Asaresult,theenergy level splitting is enhanced, and the empty energy level in the forbidden band is shifted down to valence band maximum. So, GB7a can favor the ionization in VZn-NO-H complex. Although GB7a is a special case of the twin grain boundaries, the result also gives us a new idea to understand the origin of p-type conductivity in N-doped ZnO.关键词
密度泛函理论/ZnO/孪晶界Key words
density functional theory/ZnO/twin grain boundary引用本文复制引用
吴静静,唐鑫,龙飞,唐壁玉..GGA+U方法研究ZnO孪晶界对VZn-NO-H复合体对p型导电性的影响[J].物理学报,2017,66(13):233-241,9.基金项目
国家自然科学基金(批准号: 11364009)和广西自然科学基金(批准号: 2014GXNSFFA118004)资助的课题. Project supported by the National Natural Science Foundation of China (Grant No. 11364009) and Guangxi Natural Science Foundation of China (Grant No. 2014GXNSFFA118004). （批准号: 11364009）
