Unanticipated Polarity Shift in Edge-Contacted Tungsten-Based 2D Transition Metal Dichalcogenide Transistors

Creating metal edge contacts in transition metal dichalcogenide (TMD) transistors is a promising path to advance transistor miniaturization for future technology nodes. Current experimental demonstrations nearly exclusively focus on MoS
₂
as the channel material. Here, we create edge-contacted WSe
₂
and WS
₂
transistors using a convergent Ar
⁺
ion beam source integrated within an e-beam evaporator chamber for
in-situ
processing. An unanticipated polarity shift was observed compared to top-contact behavior for Ti-WS
₂
devices, which displayed p-type conduction. Meanwhile, three distinct metal contact materials yielded comparable p-branch-dominant performance on WSe
₂
. Transmission electron microscope (TEM) imaging with energy dispersive spectroscopy (EDS) analysis indicated the existence of a residual layer of W (and chalcogen atoms to a lesser extent) beneath the metal contacts, even though the substrate was over-etched. The images presented a physically pure edge interface. This intriguing etching effect could carry significant implications for the design of tungsten-based, edge-contacted TMD transistors.