Fabrication of patternable Janus transition-metal dichalcogenides assisted by electron beam irradiation

Two-dimensional Janus transition metal dichalcogenides exhibit intrinsic out-of-plane structural symmetry breaking, which facilitates their applications in spintronics through the enhanced Rashba spin–orbit coupling. Fabrication of Janus structures in a deterministic fashion is essential for their practical heterogeneous integration, which, however, remains challenging in the aspect of material synthesis technology. Here, we demonstrate a synthetic strategy to fabricate Janus WSSe structures at definite positions on its tungsten disulfide (WS2) host through the local electron beam irradiation followed by controllable selenization. We show that the energetic electron flux can significantly modulate the WS2 lattice properties, which locally increase the energy barrier between the WS2 and its Janus counterpart WSSe, thus preventing the irradiated WS2 from being selenized and creating well-defined hetero-boundaries. Moreover, by using monolayer and bilayer WS2 as the hosts, both lateral and vertical heterostructures of WSSe–WS2 can be achieved in a patternable manner. Our work provides a viable route toward the controllable fabrication of the Janus structures for multi-functional spintronics.