Abstract
The Schottky barrier heights (SBHs) of metals on the layered transition metal dichalcogenides (TMDs) like MoS2 are calculated by density functional theory using supercell models. Despite the presence of van der Waals bonding between the layers, the metals are found to bond quite strongly to the chalcogen sites in the top contact configuration, without disturbing the intralayer covalent bonding. This allows the SBHs to follow the metal induced gap state (MIGS) model that applies to regular 3D semiconductors, and gives a pinning factor S ∼0.3. Additional pinning is caused by chalcogenide site vacancies. MoS2 is found to favor n-type devices, because the pinning levels are in its upper gap. Other compounds like MoSe2, WS2 or WSe2 have pinning levels around midgap, allowing ambipolar behavior.
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