A simple capacitor model and first-principles study of carbon-doped zigzag ZnO nanoribbons

Using density-functional-theory calculations, we study electronic and magnetic properties of zigzag ZnO nanoribbons (ZZnONRs) with a single carbon atom substituting O. We find that the formation energy of carbon dopant depends strongly on the position: the carbon atom doped close to O edge is most favorable energetically for H-passivated ZZnONRs, whereas the doped carbon atom prefers to locate near Zn edge on bare ZZnONRs. These features are explained using a simple capacitor model. We also find that the substitutional carbon defect induces spontaneous magnetization and manipulates the electronic properties of ZZnONRs, independent of the ribbon width ( N ). In particular, H-passivated N -ZZnONRs ( 4 < N < 9 ) exhibit two successive transitions from semiconductor to metal via half-metal as the doping proceeds gradually from O edge to Zn edge.