Resonance Raman spectroscopy in semiconducting transition-metal dichalcogenides: basic properties and perspectives

Raman spectroscopy is one of the most important optical techniques for the study of two-dimensional systems, providing fundamental information for the development of applications using these materials in optoelectronics and valleytronics. The emerging area of two-dimensional layered materials demands the characterization and understanding of the basic physical properties of the material under study and is indispensable to pave the way for the engineering of devices. In this review we cover the recent development of resonance Raman spectroscopy on transition metal dichalcogenides, discussing the exciton-phonon coupling and intervalley double-resonance Raman scattering process. A brief discussion of the effect of defects and disorder on the Raman spectra of these materials is also presented. The results of Raman spectroscopy in TMDs are compared to those observed in graphene, showing that this technique also provides physical information about TMDs that were previously reported in graphene systems. We also discuss the possible future perspectives and directions that the field may go to.