Metalorganic chemical vapor deposition of wafer-scale transition metal dichalcogenide monolayer and heterostructures

Metalorganic chemical vapor deposition (MOCVD) has emerged as a promising technique for scalable synthesis of transition metal dichalcogenides as it enables growth at high temperatures and chalcogen overpressures which are beneficial for epitaxial growth of monolayers and provides good control over precursor flux which is necessary for the synthesis of heterostructures. Our work has focused on MOCVD growth of epitaxial semiconducting TMDs (MoS2, WS2 and WSe2) on 2" diameter c-plane sapphire substrates. Steps on the sapphire surface can be used to control the orientation of TMD domains and reduce the number of inversion domain boundaries. In situ spectroscopic ellipsometry is demonstrated to be an effective real time monitor of TMD growth even at the sub-monolayer level which can be exploited to track surface coverage as a function of time under varying growth conditions. The ability to precisely control and modulate precursor flux during growth is used to synthesize in-plane heterostructures that enable localized exciton confinement and emission.