Direct observation of the band gap transition in atomically thin ReS${}_2$

Abstract

ReS${}_2$ is considered as a promising candidate for novel electronic and sensor applications. The low crystal symmetry of the van der Waals compound ReS${}_2$ leads to a highly anisotropic optical, vibrational, and transport behavior. However, the details of the electronic band structure of this fascinating material are still largely unexplored. We present a momentum-resolved study of the electronic structure of monolayer, bilayer, and bulk ReS${}_2$ using k-space photoemission microscopy in combination with first-principles calculations. We demonstrate that the valence electrons in bulk ReS${}_2$ are - contrary to assumptions in recent literature - significantly delocalized across the van der Waals gap. Furthermore, we directly observe the evolution of the valence band dispersion as a function of the number of layers, revealing a significantly increased effective electron mass in single-layer crystals. We also find that only bilayer ReS${}_2$ has a direct band gap. Our results establish bilayer ReS${}_2$ as a advantageous building block for two-dimensional devices and van der Waals heterostructures.

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Cited by in corpus (12)

• Complete determination of crystallographic orientation of ReX2 (X=S, Se) by polarized Raman spectroscopy
• Electronic bandstructure of ReS2 by high resolution angle resolved photoemission spectroscopy
• Pressure dependence of direct optical transitions in ReS2 and ReSe2
• Dominating Interlayer Resonant Energy Transfer in Type-II 2D Heterostructure
• Visualizing Orbital Content of Electronic Bands in Anisotropic 2D Semiconducting ReSe${}_2$
• Non equilibrium anisotropic excitons in atomically thin ReS${}_2$
• The optical signature of few-layer ReSe${}_2$
• Electronic band structure of rhenium dichalcogenides
• Two-dimensional ReS2: Solution to the Unresolved Queries on Its Structure and Inter-layer Coupling Leading to Potential Optical Applications
• Prevalence of oxygen defects in an in-plane anisotropic transition metal dichalcogenide
• Vibrational and dielectric properties of monolayer transition metal dichalcogenides
• Interplay of crystal thickness and in-plane anisotropy and evolution of quasi-one dimensional electronic character in ReSe${}_2$