Vacancies inducing electronic and optical properties in 2D ZnO:Be/Mg

The structural, electronic and optical properties of the 2D ZnO:Mg/Be with oxygen or zinc vacancies were studied by First-principles calculation. Results show that the formation of vacancy defect in DL system is easier than in SL system. The band gap become narrow with introducing oxygen and zinc vacancy defects. It was also found that oxygen vacancies can induce an impurity level near VBM to improve the conductivity of system and Zn vacancies can not. Optical absorption spectra show that oxygen vacancy defect will cause blue-shift and Zn vacancy defect will cause red-shift. So, two kinds of vacancies give birth to the opposite optical properties. Therefore, vacancy defects in 2D ZnO:Mg/Be are very important defect to better the conductivity and potential application in photoelectron and photocatalysis.