  Two-dimensional MoS2 is a crystalline semiconductor with high potential for
numerous technologies. Research in recent years has sought to exploit the
direct band gap and high carrier mobility properties of monolayer MoS2 for
functional applications. To date, the production of MoS2 has remained at the
research level and samples are usually synthesized in small quantities using
small yield, expensive techniques. In order to realize scalable MoS2-based
technology, large-area, high-quality and affordable MoS2 wafers must become
available. Here we report on MoS2 films grown on 100 mm sapphire wafers by a
chemical vapor deposition process utilizing hydrogen sulfide and molybdenum
precursor mixtures consisting of Na2MoO4 and NaCl. The grains of these films
are faceted, large-area, on the order of 1-75 microns in length on edge. Growth
conditions are identified that yield monolayer MoS2 films. Raman spectroscopy
shows an E2g and A1g peak separation of 17.9-19.1 cm-1. Photoluminescence
spectroscopy shows that annealing the films post-growth suppresses trion
emission. X-ray photoelectron spectroscopy of the annealed films shows an in
increase in the S:Mo concentration ratio from 1.90:1.00 to 2.09:1.00.
