Fluorination induced half metallicity in two-dimensional few zinc oxide layers

We systematically explore the stability, bonding characteristics, and electronic and magnetic properties of two-dimensional (2D) few zinc oxide layers (few-ZnOLs) with or without fluorination by using density functional theory approach. The pristine few-ZnOLs favor stable planar hexagonal structures, which stem from their unique bonding characteristics: The intralayer Zn-O interaction is dominated by covalent bonding while the interaction between layers is weak ionic bonding. Furthermore, we demonstrate that fluorination from one side turns the planar few-ZnOLs back to the wurtzitelike corrugated structure, which enhances the stability of the 2D ZnO films. The fluorinated few-ZnOLs are ferromagnets with magnetic moments as high as 0.84, 0.87, 0.89, and 0.72 mu(B) per unit cell for the number of layers of N=1, 2, 3, and 4, respectively. Most interestingly, the fluorination can also turn few-ZnOLs from semiconductor into half metallicity with a half-metal gap up to 0.56 eV. These excellent electronic and magnetic properties may open 2D ZnO based materials great opportunity in future spintronics.