Oriented Epitaxial Growth of Mixed-Dimensional van der Waals Heterostructures with One-Dimensional (1D) Bi2S3 Nanowires and Two-Dimensional (2D) WS2 Monolayers for Performance-Enhanced Photodetectors

The synthesis of mixed-dimensional van der Waals heterostructures with controlled alignment by chemical vapor deposition (CVD) technique remains a big challenge due to the complex epitaxial growth mechanism. Herein, we report the epitaxial growth of mixed-dimensional Bi₂S₃/WS₂ heterostructures by a two-step CVD method. Bi₂S₃ crystals grown on 2D WS₂ monolayers exhibit 1D feature with the preferred orientation, indicating a strong epitaxial growth behavior at the 1D/2D interface. Furthermore, the heterostructure was carefully characterized by transmission electron microscopy, which reveals the preferential growth of Bi₂S₃ nanowires along the zigzag edge of WS₂ monolayers. The experimental results are also consistent with the theoretical calculations by DFT, where the preferred orientation possesses minimal surface energy. The strong interaction between Bi₂S₃ and WS₂ enables efficient charge transfer of photogenerated carriers at the heterointerface, which leads to a largely improved light harvesting capability with the highest responsivity of ∼48.1 AW^-1 and detectivity of ∼5.9 × 10¹² Jones.