Prevalence of oxygen defects in an in-plane anisotropic transition metal dichalcogenide

TL;DR

This study uses advanced microscopy and calculations to identify oxygen defects in ReS₂, revealing their atomic structure and impact on the material's electronic properties, which is crucial for future device engineering.

Contribution

The paper provides the first atomic-scale identification of oxygen defects in ReS₂ using combined experimental and theoretical methods.

Findings

Oxygen atoms are absorbed at lattice defect sites.

In-plane anisotropy of ReS₂ lattice visualized.

Semiconducting gap measured via spectroscopy.

Abstract

Atomic scale defects in semiconductors enable their technological applications and realization of novel quantum states. Using scanning tunneling microscopy and spectroscopy complemented by ab-initio calculations we determine the nature of defects in the anisotropic van der Waals layered semiconductor ReS$_2$. We demonstrate the in-plane anisotropy of the lattice by directly visualizing chains of rhenium atoms forming diamond-shaped clusters. Using scanning tunneling spectroscopy we measure the semiconducting gap in the density of states. We reveal the presence of lattice defects and by comparison of their topographic and spectroscopic signatures with ab initio calculations we determine their origin as oxygen atoms absorbed at lattice point defect sites. These results provide an atomic-scale view into the semiconducting transition metal dichalcogenides, paving the way toward understanding and engineering their properties.