a Applying PVA- assisted exfoliation technique to MoS2 consistently yields large monolayer flakes. Scale bar is 20 μm. b Corresponding Raman spectra of “M” and “P” points in a. PVA does not have an overlapping Raman signature with MoS2, allowing the use of Raman spectroscopy for identifying the number of layers within the flake. c–f The spatial Raman maps of the flake in the a indicate the uniformity of its structural properties. The map was taken from the region inside the flake marked with the solid black box. In these plots, Δω is the spacing between E2g and A1g peaks, I(A1g)/I(E2g) is the ratio of the peak intensity, Γ(E2g) and Γ(A1g) are the FWHM of the peaks. Scale bars are 5 μm. g The optical image of a monolayer MoS2 encapsulated in hBN. The inset shows the spatial map of the PL peak intensity. Scale bars are 20 μm. h The representative PL spectra of the monolayer MoS2 at the encapsulated region (point “A”) and the exposed region (point “B”). The red-shift of the PL spectrum suggests the presence of a small tensile strain within the encapsulated region. The FWHM of the “A” and “B” spectra are ≈46 and 54 meV, indicating the high material quality of the exfoliated MoS2.