Phase Transition-Induced Temperature-Dependent Phonon Shifts in Molybdenum Disulfide Monolayers Interfaced with a Vanadium Dioxide Film

Abstract

We report the optical phonon shifts induced by phase transition effects of vanadium dioxide (VO2) in monolayer molybdenum disulfide (MoS2) when interfacing with a VO2 film showing a metal-insulator transition coupled with structural phase transition (SPT). To this end, the monolayer MoS2 directly synthesized on a SiO2/Si substrate by chemical vapor deposition was first transferred onto a VO2/c-Al2O3 substrate in which the VO2 film was prepared by a sputtering method. We compared the MoS2 interfaced with the VO2 film with the assynthesized MoS2 by using Raman spectroscopy. The temperature-dependent Raman scattering characteristics exhibited the distinct phonon behaviors of the E-2g(1) and A(1g) modes in the monolayer MoS2. Specifically, for the as-synthesized MoS2, there were no Raman shifts for each mode, but the enhancement in the Raman intensities of E-2g(1) and A(1g) modes was clearly observed with increasing temperature, which could be interpreted by the significant contribution of the interface optical interference effect. In contrast, the red-shifts of both the E-2g(1) and A(1g) modes for the MoS2 transferred onto VO2 were clearly observed across the phase transition of VO2, which could be plane tensile strain effect induced by the SPT and the enhancement of electron-phonon interactions density at the MoS2/VO2 interface through the electronic phase transition. This study provides further interfacial hybridization for the heterogeneous integration of 2D transition-metal dichalcogenides and explained in terms of the indue to an increased electron insights into the influence of strongly correlated materials.