Raman and PL studies of the bilayer MoS2 crystals. a Raman and b PL spectra of the as-grown AA and AB stacking bilayer MoS2, CVD-grownmonolayer MoS2 and mechanically exfoliated bilayer MoS2, where the PL signal of all bilayer samples were enlarged by 100 times in order to compare withthat of monolayer one. Optical image (c) the Raman peak intensity mappings of E12g (d) and A1g (e) as well as the PL intensity mapping of peak A (f) of theas-grown complete AA stacking bilayer MoS2. g Optical image, the Raman peak intensity mappings of E12g h and A1g i as well as the PL intensity mapping ofpeak A j of the as-grown AB stacking bilayer MoS2. The scale bar is 50 μm