  Layered metal dichalcogenide materials are a family of semiconductors with a
wide range of energy band gaps and properties, and potential to open up new
areas of physics and technology applications. However, obtaining high crystal
quality thin films over a large area remains a challenge. Here we show that
chemical vapor deposition (CVD) can be used to achieve large area electronic
grade single crystal Molybdenum Disulfide (MoS2) thin films with the highest
mobility reported in CVD grown films so far. Growth temperature and choice of
substrate were found to critically impact the quality of film grown, and high
temperature growth on (0001) orientated sapphire yielded highly oriented single
crystal MoS2 films for the first time. Films grown under optimal conditions
were found to be of high structural quality from high-resolution X-ray
diffraction, transmission electron microscopy, and Raman measurements,
approaching the quality of reference geological MoS2. Photoluminescence and
electrical measurements confirmed the growth of optically active MoS2 with a
low background carrier concentration, and high mobility. The CVD method
reported here for the growth of high quality MoS2 thin films paves the way
towards growth of a variety of layered 2D chalcogenide semiconductors and their
heterostructures.
