Insights into enhanced ferromagnetic activity of P doping graphene-ZnO monolayer with point defects

The ferromagnetic properties and origin of P doping graphene-ZnO (g-ZnO) monolayer without or with defects including O vacancy (VO) and Zn vacancy (VZn) are discussed in detail using the first principles method in this paper. In order to describe the electronic structure correctly, the GGA + U (PBE functional in GGA) method is adopted. The most stable structures of P doping g-ZnO monolayer without or with defects including VO and VZn are obtained. When O atoms in g-ZnO monolayer is replaced by P, the impurity level caused by P is near Fermi level and P-3p orbital is spin polarized, and the system is ferromagnetic. VZn produce weakly bound O-2p electrons, which spin in the same direction and leads to the ferromagnetism of g-ZnO system. Both of the mechanism can be obtained at room temperature. Meanwhile Curie temperature (Tc) of Zn16O15P1 and Zn16O14P2 is higher than room temperature. Therefore, P doping ZnO monolayer is a potential diluted magnetic semiconductor. [Display omitted] •The stable structures of P doping graphene-ZnO monolayer without or with defects including VO and VZn are obtained.•The analysis of formation energy (Ef) shows that P doping makes g-ZnO films easy to form VZn.•P doping and VZn are the ferromagnetic origin of g-ZnO monolayer.•The calculated Tc of the designed models is higher than room temperature.