title: Raman modes of MoS2 used as fingerprint of van der Waals interactions in 2-D crystal-based heterostructures.
abstract: In this work, we use Raman spectroscopy as a nondestructive and rapid technique for probing the van der Waals (vdW) forces acting between two atomically thin crystals, where one is a transition metal dichalcogenide (TMDC). In this work, MoS2 is used as a Raman probe: we show that its two Raman-active phonon modes can provide information on the interaction between the two crystals. In particular, the in-plane vibration (E2g(1)) provides information on the in-plane strain, while the out-of-plane mode (A1g) gives evidence for the quality of the interfacial contact. We show that a vdW contact with MoS2 is characterized by a blue shift of +2 cm(-1) of the A1g peak. In the case of a MoS2/graphene heterostructure, the vdW contact is also characterized by a shift of +14 cm(-1) of the 2D peak of graphene. Our approach offers a very simple, nondestructive, and fast method to characterize the quality of the interface of heterostructures containing atomically thick TMDC crystals.
authors.affiliation: School of Chemistry and ‡School of Physics and Astronomy, University of Manchester , Oxford Road, Manchester M13 9PL, U.K.
authors.forename: Kai-Ge
authors.initials: KG
authors.lastname: Zhou
authors.forename: Freddie
authors.initials: F
authors.lastname: Withers
authors.forename: Yang
authors.initials: Y
authors.lastname: Cao
authors.forename: Sheng
authors.initials: S
authors.lastname: Hu
authors.forename: Geliang
authors.initials: G
authors.lastname: Yu
authors.forename: Cinzia
authors.initials: C
authors.lastname: Casiraghi
keywords: 2D crystals; MoS2; Raman spectroscopy; heterostructures; strain; van der Waals interaction