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Project Topic
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The Graphene Flagship has produced many exciting and valuable results so far. One of the main obstacles for real uptake in the industry however is the lack of scalable processes for making large area, high quality layers and hetero-structures of graphene and other 2D layered materials, including functional device demo’s. Moreover, the interfaces in such structures are not well understood; this is critical as these interfaces and their stability during processing sequences will govern any device functioning and performance. 2Dfun aims at developing a graphene/MX2/dielectric platform based on low-temperature high-volume production compatible deposition techniques of 2D transition metal dichalcogenides (MX2) on graphene as well as high-k dielectric layers (Al2O3, HfO2) on MX2. With high-k growth based on a conventional Atomic Layer Deposition (ALD) process, we will investigate two novel routes for MX2 making: i) plasma-enhanced sulphurization of metal or metal oxide layers deposited by ALD, and ii) a direct ALD process with regular metal and chalcogen precursors. Oxford Instruments (UK) will assist in tool modification and process development for in-situ PE sulphurization. An important aspect is the functionalization of the graphene and MX2 surfaces so as to create active sites for the subsequent growth process, for which we will work with Self-Assembled Monolayers as well as some novel inorganic functionalization approaches. (IMEC, Eindhoven University of Technology, KULEUVEN Chemistry Dept.). The resulting layers and full graphene/MX2/high-k layer structures will be thoroughly analyzed for their structural, chemical, optical and electrical characteristics. Next to more conventional techniques, we will employ some novel approaches such as Second Harmonic Generation for crystallinity and Rutherford Backscattering for quantitative and stoichiometry measurements. We want to understand the detailed structure of 2D/2D (graphene/MX2) and 2D/3D (MX2/dielectric metal oxide) interfaces, as well as how the functionalization of the surface before growth has influenced the resulting interface. Especially important are aspects of charge transfer (=’doping’ from device point of view), energy distribution, gap state spectrum and band structure, as well as their stability. To this end, we will employ some novel analysis techniques (dynamic XPS in-operando, Internal Photon Emission and Photoconductivity), in combination with basic electrical approaches (I/V, C/V) and ab-initio atomistic modelling on appropriate test structures (Bilkent University Ankara, KULEUVEN Physics Dept.). Last but not least, with this graphene/MX2/high-k platform we will demonstrate and characterize the first functional hybrid MOSFET device (IMEC) made with manufacturable processes. This will lay sound foundations for exploitation plans of the results from 2Dfun, amongst which offering this platform for further development, exploration and assessment inside the Graphene Flagship.
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