Edge-Epitaxial Growth of 2D NbS -WS Lateral Metal-Semiconductor Heterostructures.

2D metal-semiconductor heterostructures based on transition metal dichalcogenides (TMDs) are considered as intriguing building blocks for various fields, such as contact engineering and high-frequency devices. Although, a series of p-n junctions utilizing semiconducting TMDs have been constructed hitherto, the realization of such a scheme using 2D metallic analogs has not been reported. Here, the synthesis of uniform monolayer metallic NbS on sapphire substrate with domain size reaching to a millimeter scale via a facile chemical vapor deposition (CVD) route is demonstrated. More importantly, the epitaxial growth of NbS -WS lateral metal-semiconductor heterostructures via a "two-step" CVD method is realized. Both the lateral and vertical NbS -WS heterostructures are achieved here. Transmission electron microscopy studies reveal a clear chemical modulation with distinct interfaces. Raman and photoluminescence maps confirm the precisely controlled spatial modulation of the as-grown NbS -WS heterostructures. The existence of the NbS -WS heterostructures is further manifested by electrical transport measurements. This work broadens the horizon of the in situ synthesis of TMD-based heterostructures and enlightens the possibility of applications based on 2D metal-semiconductor heterostructures.