Vertical and in-plane heterostructures based on van der Waals (vdW) crystals have drawn rapidly increasing attention owning to the extraordinary properties and significant application potential. However, current heterostructures are mainly limited to vdW crystals with a symmetrical hexagonal lattice, and the heterostructures made by asymmetric vdW crystals are rarely investigated at the moment. In this contribution, it is reported for the first time the synthesis of layered orthorhombic SnS–SnSSe core–shell heterostructures with well-defined geometry via a two-step thermal evaporation method. Structural characterization reveals that the heterostructures of SnS–SnSSe are in-plane interconnected and vertically stacked, constructed by SnSSe shell heteroepitaxially growing on/around the pre-synthesized SnS flake with an epitaxial relationship of (303)//(033), [010]//[100]. On the basis of detailed morphology, structure and composition characterizations, a growth mechanism involving heteroepitaxial growth, atomic diffusion, as well as thermal thinning is proposed to illustrate the formation process of the heterostructures. In addition, a strong polarization-dependent photoresponse is found on the device fabricated using the as-prepared SnS−SnSSe core–shell heterostructure, enabling the potential use of the heterostructures as functional components for optoelectronic devices featured with anisotropy.
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