Bias-dependent transport properties of passivated tilted black phosphorene nanoribbons

Abstract

Using the density functional theory incorporated with a non-equilibrium Green's function (NEGF) technique, we explored the bias-dependent transport of tilted phosphorene nanoribbons. Herein, we considered three types of nanoribbons: self-passivated (TPNR_self), H-passivated (TPNR_H), and O-passivated (TPNR_O) systems. The TPNR_self showed an indirect band gap of 0.53 eV, whereas the TPNR_H displayed a direct band gap of 1.32 eV. In TPNR_O, we observed a spin-polarized band structure with a spin-dependent band gap. We found that the bias-dependent I–V curve was dependent on the passivation effect. In TPNR_self and TPNR_H, the current monotonically increased with an external bias, but the magnitude of the current in TPNR_self was more than 10 times than that in TPNR_self. Unlike the I–V characteristics in TPNR_self and TPNR_H, the current in TPNR_O almost vanished beyond an external bias of 1.7 V. Mostly, the bias-dependent I–V was interpreted based on the band structure in the lead parts. However, we found that this conventional approach was not sufficient to analyze the I–V curve. Indeed, we showed that the detailed I–V curve could be understood by calculating the bias-dependent density of states in the scattering part related to the transmission channel. It was also found that the electron flow channel was dependent on the passivation effect and uniformly distributed over the entire nanoribbon in TPNR_self and TPNR_H. In contrast, the electron flowed mostly along the edge line in TPNR_O. Moreover, we have found that spin polarization in the conduction current can be manipulated by an external bias, and this may suggest that the TPNR_O can be utilized for potential spintronic applications.