Low wavenumber Raman spectroscopy of highly crystalline MoSe2 grown by chemical vapor deposition

Transition metal dichalcogenides (TMDs) have recently attracted attention due to their interesting electronic and optical properties. Fabrication of these materials in a reliable and facile method is important for future applications, as are methods to characterize material quality. Here we present the chemical vapor deposition of MoSe2 monolayer and few layer crystals. These results show the practicality of using chemical vapor deposition to reliably fabricate these materials. Low frequency Raman spectra and mapping of shear and layer breathing modes of MoSe2 are presented for the first time. We correlate the behavior of these modes with layer number in the materials. The usefulness of low frequency Raman mapping to probe the symmetry, quality, and monolayer presence in CVD grown 2D materials is emphasized.