Tunable electronic band structure in WSSe van der Waals Alloys

TL;DR

This study demonstrates how alloying in bulk WS2(1-x)Se2x can continuously tune the electronic band structure, providing insights into band evolution and atomic configurations for potential applications in van der Waals materials.

Contribution

It introduces a combined experimental and theoretical approach to control and understand the band structure in ternary TMD alloys, specifically WSSe, which was previously unexplored.

Findings

Band structure varies continuously with alloy composition.

Valence band splitting at K points increases from 420 to 520 meV.

Atomic configurations influence local electronic properties.

Abstract

The electronic structure of semiconducting 2D materials such as transition metal dichalcogenides (TMDs) is known to be tunable by its environment, from simple external fields applied with electrical contacts up to complex van der Waals heterostructure assemblies. However, conventional alloying from reference binary TMD compounds to composition-controlled ternary alloys also offers unexplored opportunities. In this work, we use nano-angle resolved photoemission spectroscopy (nano-ARPES) and density functional theory (DFT) calculations to study the structural and electronic properties of different alloy compositions of bulk WS2(1-x)Se2x. Our results demonstrate the continuous variation of the band structure and the progressive evolution of the valence band splitting at the K points from 420 to 520 meV in bulk WS2(1-x)Se2x. We also carried out scanning tunneling microscopy (STM) measurements and DFT to understand the possible S or Se substitutions variants in WS2(1-x)Se2x alloys, with different local atomic configurations. Our work opens up perspectives for the fine control of the band dispersion in van der Waals materials and demonstrate how the band structure can be tuned in bulk TMDs. The collected information can serve as a reference for future applications.