# Bandgap closing at the screw dislocations of WS2 spirals

## TL;DR

This paper reports the experimental observation and theoretical validation of bandgap closing at screw dislocations in WS2 spirals, revealing a pathway for creating metallic states and vertical conduction channels in TMDC-based nanoelectronic devices.

## Contribution

It provides the first experimental evidence of bandgap closing at screw dislocations in WS2 and explains the mechanism through first-principle calculations.

## Key findings

- Bandgap closes at screw dislocations in WS2 spirals.
- Dangling bonds and localized stress cause the bandgap modulation.
- Metallic states enable vertical conduction channels in TMDC devices.

## Abstract

Van der Waals (vdW) layered transition metal dichalcogenides (TMDCs) materials are emerging as one class of quantum materials holding novel optical and electronic properties. In particular, the bandgap tunability attractive for nanoelectronics technology have been observed up to 1.1 eV when applying dielectric screening or grain boundary engineering. Here we present the experimental observation of bandgap closing at the center of the screw dislocation-driven WS2 spiral pyramid by means of scanning tunneling spectroscopy, which is validated by first-principle calculations. The observed giant bandgap modulation is attributed to the presence of dangling bonds induced by the W-S broken and the enhanced localized stress in the core of the dislocation. Achieving this metallic state and the consequent vertical conducting channel presents a pathway to 3D-interconnected vdW heterostructure devices based on emergent semiconducting TMDCs.

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Source: https://tomesphere.com/paper/1906.07076