Tunnelling Characteristics of Stone-Wales Defects in Monolayers of Sn and Group-V Elements

TL;DR

This study explores how Stone-Wales defects influence the electronic and tunnelling properties of monolayers of Sn and group-V elements, revealing defect-dependent electronic behavior and distinctive STM signatures.

Contribution

It provides detailed analysis of the impact of SW-defects on electronic properties and tunnelling characteristics of Sn and group-V monolayers, including simulated STM images for defect identification.

Findings

Defective stanene has a near-zero band gap at certain defect concentrations.

SW-defects induce conduction states in group-V monolayers, facilitating electron tunnelling.

Distinct STM features can identify topological defects in these monolayers.

Abstract

Topological defects in ultrathin layers are often formed during synthesis and processing, thereby, strongly influencing their electronic properties . In this paper, we investigate the role of Stone-Wales (SW) defects in modifying the electronic properties of the monolayers of Sn and group-V elements. The calculated results find the electronic properties of stanene (monolayer of Sn atoms) to be strongly dependent on the concentration of SW-defects e.g., defective stanene has nearly zero band gap (~ 0.03 eV) for the defect concentration of 2.2 x 10^13 cm^-2 which opens up to 0.2 eV for the defect concentration of 3.7 x 10^13 cm^-2. In contrast, SW-defects appear to induce conduction states in the semiconducting monolayers of group-V elements. These conduction states act as channels for electron tunnelling, and the calculated tunnelling characteristics show the highest differential conductance for the negative bias with the asymmetric current-voltage characteristics. On the other hand, the highest differential conductance was found for the positive bias in stanene. Simulated STM topographical images of stanene and group-V monolayers show distinctly different features in terms of their cross-sectional views and distance-height profiles which can serve as fingerprints to identify the topological defects in the monolayers of group-IV and group-V elements in experiments.