Role of line defect in the bandgap and transport properties of silicene nanoribbons

TL;DR

This paper investigates how line defects influence the electronic bandgap and transport properties of silicene nanoribbons, revealing ways to modulate these properties for device applications using on-site energies and spin-orbit interactions.

Contribution

It introduces a detailed analysis of defect-induced bandgap modulation in silicene nanoribbons using tight-binding and NEGF methods, highlighting new control mechanisms for electronic properties.

Findings

Line defects open a bulk energy gap due to sublattice symmetry breaking.

Transport properties can be modulated by on-site energy, sublattice potential, and spin-orbit coupling.

Presence of quantum spin Hall states induced by spin-orbit coupling.

Abstract

By using the tight-binding model and non-equilibrium Green's function method (NEGF), we study the band structures and transport properties of a silicene nanoribbon with a line defect where a bulk energy gap is opened due to the sublattice symmetry breaking. The flat subband bends downwards or upwards due to the effect of the line defect. The spin-orbit coupling induces quantum spin Hall states. Especially, the energy band depends on the distance between the line defect and the edge of the nanoribbon. The effects of the on-site energies on the band spectra of the two defect configurations are different. There always exists one band gap for different on-site energies for the defect configuration of case 1. However, a gapless state and a band gap can be modulated by changing the on-site energy, the sublattice potential and spin-orbit couplings for the defect configuration of case 2. Accordingly, the variation trends of the conductance including zero conductance can be well understood in terms of the combined effect of the sublattice potential, the on-site energy and spin-orbit couplings on the band structures. Thus it is easy and effective to modulate the transport property of the silicene nanoribbon with the defect configuration of case 2 by utilizing the sublattice potential, the on-site energy and spin-orbit couplings. This study is of great significance for the fabrication and the modulation of the transport property of silicene-based devices.