Strain-modulated optical response in 2D MoSe2 made by Na-assisted CVD on glass.

Extended investigations on 2D transition metal dichalcogenides (TMDCs) have opened sound possibilities to apply these materials in several technological fields such as sensing. To this end, fully reproducible methods for the wafer-scale production of crystalline and uniform 2D TMDCs are in demand. In this work, atomically thin MoSe₂ was grown by atmospheric-pressure chemical vapor deposition using the Na-assisted process with Se powder and Mo foil precursors on a glass substrate. The samples were extensively characterized via Raman and photoluminescence spectroscopy, atomic force microscopy, transmission electron microscopy, and x-ray photoelectron spectroscopy. The MoSe₂ samples consist of submillimeter, monolayer single-crystals with 2H phase configuration. Being monolayer and crystalline, the samples exhibit well-defined and intense photoluminescence. CVD-grown 2D MoSe₂ was integrated into a device with strain-tunable optical properties and tested. Under tensile strain (in the range of 0.2%–0.4%), the spectral emission responded to an in-plane strain with marked peak shifts toward lower energies for increasing levels of strain (∼3 and ∼2 nm shift for the main PL component at 0.2% and 0.4%, respectively), indicating a reduction of the bandgap. [ABSTRACT FROM AUTHOR]