B. Munkhbat, P. Wrobel, T. J. Antosiewicz, T. O. Shegai. Optical constants of several multilayer transition metal dichalcogenides spectroscopic ellipsometry in the 300–1700 nm range: High index, anisotropy, and hyperbolicity, ACS Photonics9, 2398–2407 (2022) (Numerical data kindly provided by Tomasz Antosiewicz)
Tungsten disulfide (WS2) is a layered transition metal dichalcogenide that possesses distinct properties based on its structural morphology. In its three-dimensional bulk form, WS2 has indirect bandgap semiconducting properties, which contrasts its behavior when isolated to a monolayer or few-layer forms. When exfoliated to these thin layers, WS2 undergoes a transition to a direct bandgap semiconductor, making it intriguing for potential applications in electronics, optoelectronics, and photonics. This material's unique hexagonal structure gives it excellent lubrication capabilities, often preferred in environments with high pressures and temperatures. Furthermore, research continues into its promise in nanoelectronic devices, spintronic applications, and as a component in heterostructures with other two-dimensional materials.