Wrinkle and near-resonance effects on the vibrational and electronic properties in compressed monolayer MoSe2

Abstract

Pressure has been considered as an effective technique to modulate the structural, electronic, and optical properties of transition metal dichalcogenide (TMDs) materials. Here, by performing in situ high pressure Raman, photoluminescence (PL) and absorption measurements, we systematically investigated the vibrational and electronic properties evolution of monolayer MoSe₂ grown on a SiO₂/Si substrate under high pressure. When the pressure increased up to 4.84 GPa, an unexpected phonon mode at 367 cm⁻¹ appeared, which was identified as the Raman-inactive A₂′′ mode and was activated under high pressure. Combined with the analysis of absorption spectroscopy, this phenomenon can be attributed to the pressure-induced wrinkle and near-resonance effects in compressed monolayer MoSe₂. Subsequently, A₁′ split into two peaks after 7.44 GPa, providing further distinct evidence for the pressure-induced wrinkle effect in compressed monolayer MoSe₂. Moreover, this wrinkle effect can also lead to a rapid quenching of photoluminescence in monolayer MoSe₂. These results suggest that the substrate plays an important role in determining the vibrational and electronic properties of compressed monolayer MoSe₂, and can provide valuable information on the electronic and optoelectronic applications of monolayer MoSe₂ under extreme conditions.