Single-Step Fabrication of Transition Metal Dichalcogenide Lateral Heterojunctions Using Helium-Focused Ion Beam Lithography

Although semiconductor two dimensional (2D) materials are of great interest for atomically thick nanoelectronics, the production of in-plane heterojunctions using 2D transition metal dichalcogenides (TMDs) still remains challenging. We found that using high-resolution helium focused ion beam (He-FIB), we were able to tune the optoelectronic properties of WS₂ and WSe₂ in order to produce in-plane heterostructures through defect engineering. In this work, we bombarded CVD-grown monolayer WSe₂ and WS₂ with He ions to produce a photoresist-free heterojunction. We investigated the optoelectronic properties at the interface between the pristine and bombarded regions with Raman and photoluminescence spectroscopies as well as Kelvin probe force microscopy (KPFM). Density functional theory (DFT) calculations allowed us to show that chalcogen vacancy sites play a major role in tuning the work function value. By taking into account the effect of electronic doping, we could elucidate the charge transfer mechanisms at the interface between pristine and bombarded material. We demonstrated that a single nanopatterning step resulted in the fabrication of 2D materials heterojunctions.