Effects induced by single and multiple dopants on the transport properties in zigzag-edged graphene nanoribbons

Abstract

The effects of boron and nitrogen doping on the transport properties of zigzag-edged graphene nanoribbons ZGNRs with antiferromagnetically coupled edge states are investigated by first-principles electronic structure combined with a nonequilibrium Green?s function technique. Specifically, the effects produced by single and multiple impurities as a function of their distance from the edges are analyzed. It is found that the introduction of single B or N atoms induces bound states and quasibound states in ZGNRs, which can be observed as dips or peaks in the electron transmission function. In particular, the transmission channel associated to the edge states is strongly suppressed when the impurities are close to the edges. Multiple impurities in general interfere and modify further the transmission function. However, if the impurities are placed at positions such that the associated bound and quasibound states appear at opposite sides of the Fermi level, then the transmission can be rationalized as a simple superposition of the transmission function of individually doped ribbons. Finally, an interesting situation appears for B and N codoping, since fully spin-polarized transmission peaks are generated at energies corresponding to the ribbon gap. This offers the hope of using such nanoribbons for low-bias spin-polarized tunneling in spintronics applications