Strain dependence of electronic properties and effective masses of monolayer ZnO from density functional theory

This work focuses on the calculation of electronic properties and effective masses of ZnO monolayer under homogeneous biaxial strains. We have employed density functional theory (DFT) with generalized gradient approximation (PBE-GGA) as exchange correlation. The optimized lattice constant of 2D-ZnO monolayer is found to be 3.31 Å. The structure remains stable in its hexagonal lattice within the range of biaxial strain chosen in this work, from δ=-3.32 % to δ=+2.20%. Under normal condition 2D-ZnO monolayer exhibits a direct band gap with electron transitions along Г-Г symmetry points. However, under compression and extension the majority carrier flips from n-type to p-type, respectively. The variation of energy band gaps within UV-IR energy range predicts this material to be a potential candidate for optoelectronics. The calculated effective masses of both electrons and holes are in good agreement with the available data.