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

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.