Investigations on electronic properties and optical properties of Zn9-xAgxO/G based on first-principles

Abstract

In order to enhance the interaction between ZnO monolayer （ZnO-ML） and graphene monolayer (G), the photoelectric properties of G, ZnO-ML, Ag-doped ZnO-ML (Zn9-xAgxO) (X = 1, 2, 3, 4), and Zn9-xAgxO composite G (Zn9-xAgxO/G) were investigated based on density functional theory (DFT). Then, Band structure, partial density of state (PDOS), differential charge density, and absorption spectrum were analyzed. Compared with ZnO-ML/G where no charge transition exists between G and ZnO-ML, the graphene layer has varying degrees of charge depletion and charges mainly accumulate around the oxygen atom for Zn9-xAgxO/G with the addition of Ag atom. The Dirac points characteristics of graphene are still retained and the Dirac points are all above the impurity band and the Fermi level enters the valence band which leads to the form of p-type doping for Zn9-xAgxO/G. PDOS shows that Ag doping causes the redistribution of energy state density of each atom, promoting the coupling of C-p and O-p orbitals. Meanwhile, Ag-d also has a strong coupling with C-p. In addition, for ZnO-ML/G, the absorption peak intensity at 8 eV corresponding ZnO and 14.3 eV corresponding graphene decreases significantly. Moreover, for Zn9-xAgxO/G, the absorption strength is much greater than that of G, ZnO-ML and Zn9-xAgxO, entirely. The results can provide more theoretical support for the photoelectric properties for graphene-reinforced ZnO matrix composite.