Electronic and Optical Properties of Al, Eu Single-Doped and Al-Eu Co-Doped ZnO
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https://doi.org/10.1007/s11837-020-04494-w Ó 2020 The Minerals, Metals & Materials Society
ZINC OXIDE NANOTECHNOLOGY
Electronic and Optical Properties of Al, Eu Single-Doped and Al-Eu Co-Doped ZnO ZHENGGUANG GUO,1 SHOUHONG CHEN,1 and PING YANG1,2 1.—Laboratory of Advanced Design, Manufacturing and Reliability for MEMS/NEMS/OEDS, School of Mechanical Engineering, Jiangsu University, Zhenjiang 212013, People’s Republic of China. 2.—e-mail: [email protected]
The geometric structure, energy band structure, electronic state density and optical properties of undoped, Al single-doped, Eu single-doped and Al-Eu codoped ZnO were systematically investigated by using first principles. From the analysis of the results before and after doping, it is found that the conduction band of the doped system moves to the low energy direction, and the Fermi level enters the conduction band, showing the properties of a n-type semiconductor. In terms of optical properties, the absorption coefficient and reflectivity of Al-ZnO in the visible light region are very low, indicating that it has a high light transmittance in the visible light region. On the contrary, EuZnO and (Al, Eu)-ZnO have very high absorption coefficients and reflectivity in the visible and ultraviolet regions, and the absorption span is significantly larger than that of intrinsic ZnO. This provides a certain theoretical reference for the study of new light protection devices.
INTRODUCTION ZnO is a typical II–VI group wide-bandgap semiconductor oxide with a band gap of 3.37 eV under normal temperature and pressure conditions. The exciton binding energy reaches 60 meV, and the chemical bond formed between Zn-O atoms belongs to the transition type between an ionic bond and covalent bond.1–3 In general, due to defects such as oxygen vacancies (VO) and interstitial zinc (Zni), intrinsic ZnO appears as an n-type semiconductor, but its photoelectric characteristics are not stable enough and are greatly affected by environmental factors.4–6 Many scholars have demonstrated that ZnO thin film with good stability can be obtained by doping a small amount of certain specific elements.7–14 In recent years, rare earth metals have gradually become the focus of research on doped ZnO systems due to their very unique outermost electronic structure.15,16 For example, Hasabeldam et al.17 successfully prepared Eu-doped ZnO thin films with different concentrations using sol–gel spin coating technology. With increasing Shouhong Chen: Co-first author. (Received July 31, 2020; accepted November 7, 2020)
Eu3+ concentration, the particle size and band gap decrease. Qu et al.18 studied the changes of optical properties of Eu-doped ZnO with or without O vacancy by method of simulation and found that the absorption spectrum for single-doped systems is red shifted. Najafi et al.19 synthesized ZnO nanosheets co-doped with Al and Eu by the hydrothermal method and found that extrinsic doping and intrinsic defects play an important role in indirectly exciting Eu ions to transfer energy. Although ma
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