Influence of Cu dopant on the electronic and optical properties of graphene-like ZnO monolayer

We have performed first principles to study the electronic and optical properties of Cu-doped ZnO monolayer. ZnO monolayer has both the properties of ZnO and 2D material, which is a promising material for construction of next generational electronic and optical devices. Cu doping is a method to get a p-type semiconductor and tune the optical properties, simultaneously. Our calculated formation energy shows the formation of an oxygen vacancy is easier than zinc vacancy during preparation. The band and density of states do not show Cu is a p-type doping in ZnO monolayer though Cu-doped bulk ZnO is p-type. Cu and intrinsic vacancy induce band levels between the band gap. Cu also induced a peak around the visible, near ultraviolet region. On the other hand, oxygen vacancy enhances the peak in the ultraviolet region and zinc vacancy enhances the absorption in the visible region. The colorful optical properties extend the applications of Cu-doped ZnO monolayer. We use photocatalytic applications as an example to demonstrate an application of (Zn,Cu)O monolayer. The possible reaction mechanism of Cu-doped ZnO monolayer was analyzed. Our studies not only stimulate future studies but also pave a mad for broad applications of Cu-doped ZnO monolayer.