First-principles investigations of optoelectronic properties of ZnO and ZnO(0001) monolayersBakhtiar Ul Haq, S. AlFaify and R. AhmedEur. Phys. J. Plus, 136 2 (2021) 251DOI: https://doi.org/10.1140/epjp/s13360-021-01197-2