Molybdenum disulfide (MoS2) is a transition metal dichalcogenide, which along with graphene, has a great potential to become a material of choice for the next generation of nanoelectronics. We report the synthesis of a large-area MoS2 obtained by sulfurization of MoO3 using chemical vapor deposition (CVD) at different Ar base pressures. The optimal pressure for the growth was found to be similar to 50 mbar (millibar). The evolution of MoS2 phase as a function of Ar gas pressure was monitored by confocal Raman spectroscopy. As synthesized MoS2 shows direct bandgap of 1.6 eV evaluated by UV-vis spectroscopy. We report for the first time the valence band spectra and the work function of MoS2 on SiO2/Si calculated by ultraviolet photoemission spectroscopy, which was found to be 4.67 eV. In-situ electrical measurements demonstrated expected semiconducting behavior of the grown triangular crystals. These studies show MoS2 crystallites growth by controlling the parameters in CVD process.