Pulsed thermal deposition of transition metal dichalcogenides

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Transition metal dichalcogenides (TMDC) are most intriguing members of the two-dimensional van-der-Waals material class. In terms of fundamental electronic properties and conductivity, TMDCs span the range from metal (group V TMDCs) to semiconductor (group VI TMDCs). The optical response of the semiconducting TMDCs is governed up to room temperature by Coulombically bound neutral and charged excitons (trions). They are responsible for the high light-matter interaction cross section and photoluminescence yield when TMDCs are thinned to the monolayer regime. These favorable optical properties are complemented by fairly high charge carrier mobility, up to a few hundred square centimeters per volt second, as well as the feasibility of p- and n-doping. To pave the way for practical applications of TMDCs in devices, a fabrication method is required which allows reproducible preparation of alloys with defined composition as well as continuous growth of multiple layers of alternating materials with clean and atomically sharp interfaces. The overarching goal of the project is to attain a reliable knowledge-based fabrication route for structurally perfect wafer-scale TMDC vertical heterostructures, and to unravel its feasibility to realize complex heterostructures that enable desired optoelectronic functions. This includes band gap engineering and controllable doping of TMDCs at the monolayer level and precise control of the layer thickness in multilayer structures. Achieving these goals requires detailed understanding of the nucleation mechanisms and growth kinetics of TMDCs on different substrates, as well as a comprehensive characterization of the fundamental physical properties of the novel synthetized materials.