Defect-assisted reversible phase transition in mono- and few-layer ReS$_2$

TL;DR

This study uncovers a light-induced reversible phase transition in mono- and bilayer ReS$_2$, facilitated by sulfur vacancies, enabling active control of its crystal structure for potential applications.

Contribution

It demonstrates a reversible phase transition mechanism in ReS$_2$ driven by light and electron energy, with insights from microscopy, spectroscopy, and DFT calculations.

Findings

ReS$_2$ undergoes a reversible transition from T'' to H' phase.

Sulfur vacancies facilitate the phase transition.

The transition can be induced by femtosecond laser or energetic electrons.

Abstract

Transition metal dichalcogenide (TMD) materials have attracted substantial interest due to their remarkable excitonic, optical, electrical, and mechanical properties, which are highly dependent on their crystal structure. Controlling the crystal structure of these materials is essential for fine-tuning their performance, $\textit{e.g.}$, linear and nonlinear optical, as well as charge transport properties. While various phase-switching TMD materials, like molybdenum telluride (MoTe$_2$), are available, their transitions are often irreversible. Here, we investigate the mechanism of a light-induced reversible phase transition in mono- and bilayer flakes of rhenium disulfide (ReS$_2$). Our observations, based on scanning transmission electron microscopy, nonlinear spectroscopy, and density functional theory calculations, reveal a transition from the ground T$''$ (double distorted T) to the metastable H$'$ (distorted H) phase under femtosecond laser irradiation or influence of highly-energetic electrons. We show that the formation of sulfur vacancies facilitates this phenomenon. Our findings pave the way towards actively manipulating the crystal structure of ReS$_2$ and possibly its heterostructures.