Tunable Magnetism in a Nonmetal-Substituted ZnO Monolayer: A First-Principles Study

We have studied structural, electronic, and magnetic properties of the graphene-like ZnO monolayer doped with nonmetal species using the first-principles calculations. Particular attention has been placed on the ZnO monolayer with one or two oxygen atoms per supercell substituted by carbon, boron, or nitrogen atoms. We find that the ZnO monolayer with one oxygen atom per supercell substituted by a carbon or boron atom is ferromagnetic (FM) half metal (HM), while that with a nitrogen atom per supercell is a FM semiconductor. Upon the ZnO monolayer with two oxygen atoms per supercell substituted by carbon or boron, the magnetic properties vary, depending on the distance between two impurities. Two neighboring carbon or boron atoms in the ZnO monolayer form dimer pairs, which convert the ZnO monolayer into an n-type semiconductor with a nonmagnetic (NM) ground state. As the distance between two carbon or boron atoms increases, the doped ZnO monolayer undergoes both NM AFM-FM and semiconductor HM transitions. However, the ZnO monolayer with two N atoms per supercell is a p-type semiconductor with the antiferromagnetic (AFM) ground state, regardless of the distance between N atoms. The negligible energy difference between AFM and FM states of the N-doped ZnO monolayer implies it exhibits paramagnetic behavior at room temperature. Our study demonstrates that nonmetal-doped ZnO monolayers possess tunable magnetic and electronic properties, suitable for applications in electronics and spintronics at nanoscale.