  MoS2 is a highly interesting material system, which exhibits a crossover from
an indirect band gap in the bulk crystal to a direct gap for single layers.
Here, we perform a direct comparison between large-area MoS$_2$ films grown by
chemical vapor deposition (CVD) and MoS$_2$ flakes prepared by mechanical
exfoliation from natural bulk crystal. Raman spectroscopy measurements show
differences between the in-plane and out-of-plane phonon mode positions in
CVD-grown and exfoliated MoS$_2$. Photoluminescence (PL) mapping reveals large
regions in the CVD-grown films that emit strong PL at room temperature, and
low-temperature PL scans demonstrate a large spectral shift of the A exciton
emission as a function of position. Polarization-resolved PL measurements under
near-resonant excitation conditions show a strong circular polarization of the
PL, corresponding to a valley polarization.
