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  • Received: Aug. 20, 2019

    Accepted: --

    Posted: Sep. 17, 2020

    Published Online: Sep. 17, 2020

    The Author Email: Huang Bing-Quan (huangbingquan2016@email.szu.edu.cn)

    DOI: 10.7498/aps.68.20191258

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    Bing-Quan Huang, Tie-Ge Zhou, Dao-Xiong Wu, Zhao-Fu Zhang, Bai-Kui Li. Properties of vacancies and N-doping in monolayer g-ZnO: First-principles calculation and molecular orbital theory analysis[J]. Acta Physica Sinica, 2019, 68(24): 246301-1

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Acta Physica Sinica, Vol. 68, Issue 24, 246301-1 (2019)

Properties of vacancies and N-doping in monolayer g-ZnO: First-principles calculation and molecular orbital theory analysis

Huang Bing-Quan1, Zhou Tie-Ge2, Wu Dao-Xiong3, Zhang Zhao-Fu4, and Li Bai-Kui1,*

Author Affiliations

  • 1College of Physics and Optoelectronic Engineeing, Shenzhen University, Shenzhen 518060, China
  • 2College of Electronic Information and Optical Engineering, Nankai University, Tianjin 300350, China
  • 3Hefei National Laboratory of Physical Sciences at the Microscale, University of Science and Technology of China, Hefei 230026, China
  • 4Department of Engineering, Cambridge University, Cambridge CB2 1PZ, United Kingdom

Abstract

The geometric structure, electronic structure, magnetic properties and absorption spectrum of graphene-like ZnO (g-ZnO) monolayer supercell with defects are systemically studied by the first-principles calculation based on density functional theory in this work. The defect supercell model includes zinc atom vacancy (VZn_g-ZnO), oxygen atom vacancy (VO_g-ZnO), nitrogen atom substituted for oxygen atom (NO_g-ZnO) and nitrogen adsorbed on the g-ZnO monolayer (N@g-ZnO). The results indicate that the geometric deformation induced by N-doping in NO_g-ZnO and N@g-ZnO structure is negligible, while that of supercell with vacancy is relatively large. The O atoms neighboring a Zn vacancy center in VZn_g-ZnO model move away from each other as a result of symmetry breaking. As a contrast, three N atoms around VO center move into VZn_g-ZnO supercell. The pristine g-ZnO is non-magnetic. But the magnetic moment of VZn_g-ZnO is 2.00 μB in total as a result of symmetry breaking. The partial magnetic moment mainly results from the p-orbitals of the three neighboring O atoms. VO_g-ZnO has no magnetic moment, but possesses the electronic structure with identical spin-up and spin-down. The total magnetic moment of the N-doped NO_g-ZnO is 1.00 μB, and the total magnetic moment of N@g-ZnO is 3.00 μB. Their local magnetic moments are mainly contributed by the p-orbitals of N atom. The density of states and the spin density are given to analyze the magnetic properties. Based on the supercell local symmetry and molecular orbital theory, the origin of magnetic moment is well explained. The magnetic VZn_g-ZnO, NO_g-ZnO and N@g-ZnO supercell are found to have a D3h, D3h and C3v local symmetry, respectively, which well explains that their total magnetic moments are 2.00 μB, 1.00 μB and 3.00 μB, respectively. The optical absorption characteristics are also discussed. An enhancement of light absorption can be observed for the defective supercells, due to the introduction of defect states into the band gap. The optical transition between gap state and valance band leads to the below band gap absorption. These results are of insightful guidance for understanding properties of graphene-like ZnO monolayer as well as g-ZnO with vacancy and N dopant, and can be theoretically adopted for investigating the nano-electronic devices and catalytic applications based on g-ZnO monolayer.

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