Novel single-layer vanadium sulphide phases

TL;DR

This paper reports the first successful synthesis of single-layer VS2 on Au(111), introduces a reversible S-depletion process creating a new 2D compound, and characterizes these phases with multiple surface analysis techniques.

Contribution

First realization of single-layer VS2 epitaxially grown on Au(111), including a reversible S-depletion process to form a novel 2D phase without bulk analogues.

Findings

Successfully prepared high-quality single-layer VS2

Depletion of S creates a new 2D phase

Reversible transition between phases upon annealing

Abstract

VS2 is a challenging material to prepare stoichiometrically in the bulk, and the single layer has not been successfully isolated before now. Here we report the first realization of single-layer VS2, which we have prepared epitaxially with high quality on Au(111) in the octahedral (1T) structure. We find that we can deplete the VS2 lattice of S by annealing in vacuum so as to create an entirely new two-dimensional compound that has no bulk analogue. The transition is reversible upon annealing in an H2S gas atmosphere. We report the structural properties of both the stoichiometric and S-depleted compounds on the basis of low-energy electron diffraction, X-ray photoelectron spectroscopy and diffraction, and scanning tunneling microscopy experiments.