One-Step Synthesis of a Bilayer MoS2/WS2 Lateral Heterojunction for Photoelectric Detection

Different transitional-metal dichalcogenides (TMDs) can form lateral heterojunctions by epitaxial growth. TMD heterojunctions exhibit unique optical and electrical properties by seamlessly connecting atoms at the interface. Bilayer (BL) TMDs with nanoscale thicknesses have higher state density, mobility, and room temperature stability than monolayer (ML) TMDs, so they may be more suitable for optoelectronic device applications. However, the synthesis of BL lateral heterojunctions is challenging due to the uncontrolled orientation of the second layer stacking. We report a method to grow lateral heterojunctions of BL TMDs by self-assembly epitaxy. The number of nucleation layers can be controlled by the Mo/S ratio. The BL lateral heterojunctions synthesized by this method are all AB stacking, which effectively avoids the simultaneous existence of vertical and lateral heterojunctions in AA′ stacking. After the alkaline precursor solution is spun, the binding ability of WO42– or MoO42– ions to sulfur atoms is different. Sulfur atoms preferentially combine with MoO42– ions to form MoS2, resulting in a lateral heterojunction with a sharp interface. The BL lateral heterojunction has a better photoelectric detector performance than the ML. This work provides a method for the synthesis of BL lateral heterojunctions.