Effect of VZn/VO on Stability, Magnetism, and Electronic Characteristic of Oxygen Ions for Li-Doped ZnO

The effects of Zn/O vacancy (V-Zn/V-O) and different proportions of Li/V-Zn on the magnetism of Li-doped ZnO are analyzed through first-principle calculation by using generalized gradient approximation+ U (GGA+U) under density functional theory. Results reveal that Li-doped ZnO with V-Zn can realize ferromagnetic long-range order and has a Curie temperature above room temperature. Under different proportions of Li/V-Zn (i.e., 1:1, 1:2, and 2:2) in ZnO (2 x 2 x 4), the doping system containing 2Li/2V(Zn) (Zn28Li2O32) shows the greatest magnetic moment and the smallest differential charge density. These characteristics pave the way for enhancing the magnetic properties of dilute magnetic semiconductors. The oxygen atoms in Zn28Li2O32 show acceptor and donor characteristics and exist in the forms of itinerant electrons (O1-) and local electrons (O2-), which have different effects on Zn28Li2O32 magnetism. The spin-polarization double-exchange effect among the unpaired itinerant electron (O1-) orbit, local electron (O2-) orbit, and unpaired Zn-3d electron orbit is the origin of magnetism for Li-doped ZnO with V-Zn. By contrast, the doping systems of Li-doped ZnO with V-O are nonmagnetic, rendering such systems inapplicable.