Influence of Co doping concentrations and strains on the electronic structure and absorption spectrum of graphene-like ZnO monolayer

The graphene-like ZnO(gZnO) monolayer systems have been experimentally and theoretically widely studied. And recently, more specifically the preparation of Co-doped two-dimensional ZnO. In this work, the stability, band structures and absorption spectrum of Co doping gZnO monolayer systems with the varying doping concentrations and strains have been investigated by using the first-principles plane-wave ultra-soft pseudopotential method based on the density functional theory. The results show that the Co doped gZnO monolayer systems are stable. The band gap is narrowed by Co doping, and becomes narrower with the increase of doping concentration, in addition to that the band gap is narrowed as the strain increases. The estimated Curie temperature(Tc) value is about 695 K. The covalent bond becomes stronger and the ionic bond becomes weaker as Co doing concentration increases. The absorption spectrum has a red-shift by Co doping, and heavier doping level leads to more significant red-shift, meanwhile, the absorption spectrum has a blue-shift as the strain increases. This results may be helpful for the designing of new-type gZnO-based spintronic materials and optical devices.