Proceedings of nanoGe Fall Meeting19 (NFM19)
DOI: https://doi.org/10.29363/nanoge.nfm.2019.035
Publication date: 18th July 2019
Two-dimensional (2-D) materials beyond graphene, e.g. MoS2, MoSe2, WS2, as well as other transition metal dichalcogenides (TMDs), are attracting a lot of attention from the scientific community due to their excellent transport properties given their sub-nanometer thickness and their possible application as future logic switches at the end of Moore's scaling law. Despite these promising features, 2-D materials are still far from reaching their optimal performance, mainly because of the quality of the underlying crystals and the difficulty to fabricate components with low contact resistances. To address these issues, shed light on the intrinsic potential of 2-D compounds, and support the on-going experimental activity, device simulation can be of great help, provided that tools capturing the physics at play are available. First-principles quantum transport approaches lend themselves perfectly to these tasks as they account for all necessary quantum mechanical, bandstructure, and atomistic effects present in 2-D materials. In this presentation, we will introduce such a state-of-the-art device simulator that relies on density-functional theory (DFT), maximally localized Wannier functions, and the Non-equilibrium Green's Function (NEGF) formalism [1]. It will be applied to the calculation of the carrier mobility and "current vs. voltage" characteristics of conventional TMDs and to the investigation of more exotic 2-D materials whose existance has been recently theoretically postulated [2]. Finally, the origin of the high contact resistance observed in single-layer MoS2 with a Titanium electrode on top of it will be discussed, highlighting the mechanisms responsible for the transfer of carriers from metals into monolayer structures [3].
This work was supported in part by the MARVEL National Centre of Competence in Research of the Swiss National Science Foundation, by ETH Zürich under Grant ETH-32 15-1, and by the Swiss National Science Foundation under project 175479 (ABIME).
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