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Strong Substrate Strain Effects in Multilayered WS 2 Revealed by High-Pressure Optical Measurements

2022; American Chemical Society; Volume: 14; Issue: 17 Linguagem: Inglês

10.1021/acsami.2c01726

1944-8252

Robert Oliva, Tomasz Woźniak, Paulo E. Faria, Filip Dybała, Jan Kopaczek, Jaroslav Fabian, P. Scharoch, R. Kudrawiec,

Graphene research and applications

The optical properties of two-dimensional materials can be effectively tuned by strain induced from a deformable substrate. In the present work we combine first-principles calculations based on density functional theory and the effective Bethe–Salpeter equation with high-pressure optical measurements to thoroughly describe the effect of strain and dielectric environment onto the electronic band structure and optical properties of a few-layered transition-metal dichalcogenide. Our results show that WS2 remains fully adhered to the substrate at least up to a −0.6% in-plane compressive strain for a wide range of substrate materials. We provide a useful model to describe effect of strain on the optical gap energy. The corresponding experimentally determined out-of-plane and in-plane stress gauge factors for WS2 monolayers are −8 and 24 meV/GPa, respectively. The exceptionally large in-plane gauge factor confirms transition metal dichalcogenides as very promising candidates for flexible functionalities. Finally, we discuss the pressure evolution of an optical transition closely lying to the A exciton for bulk WS2 as well as the direct-to-indirect transition of the monolayer upon compression.