No abstract

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–SnSxSe(1−x) core–shell heterostructures with well‐defined geometry via a two‐step thermal evaporation method. Structural characterization reveals that the heterostructures of SnS–SnSxSe(1−x) are in‐plane interconnected and vertically stacked, constructed by SnSxSe(1−x) shell heteroepitaxially growing on/around the pre‐synthesized SnS flake with an epitaxial relationship of (303)SnS//(033)SnSxSe(1−x), [010]SnS//[100]SnSxSe(1−x). 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−SnSxSe(1−x) core–shell heterostructure, enabling the potential use of the heterostructures as functional components for optoelectronic devices featured with anisotropy.

Inorganic cesium lead halide perovskite (CsPbX 3 , X = Cl, Br, I) is a promising material for developing novel electronic and optoelectronic devices. Despite the substantial progress that has been made in the development of large perovskite single crystals, the fabrication of highquality 2D perovskite single-crystal films, especially perovskite with a low symmetry, still remains a challenge. Herein, large-scale orthorhombic CsPbBr 3 single-crystal thin films on zinc-blende ZnSe crystals are synthesized via vapor-phase epitaxy. Structural characterizations reveal a "CsPbBr 3 (110)//ZnSe(100), CsPbBr 3 [−110]//ZnSe[001] and CsPbBr 3 [001]// ZnSe[010]" heteroepitaxial relationship between the covering CsPbBr 3 layer and the ZnSe growth substrate. It is exciting that the epitaxial film presents an in-plane anisotropic absorption property from 350 to 535 nm and polarization-dependent photoluminescence. Photodetectors based on the epitaxial film exhibit a high photoresponsivity of 200A W −1 , a large on/off current ratio exceeding 10 4 , a fast photoresponse time of about 20 ms, and good repeatability at room temperature. Importantly, a strong polarizationdependent photoresponse is also found on the device fabricated using the epitaxial CsPbBr 3 film, making the orthorhombic perovskite promising building blocks for optoelectronic devices featured with anisotropy.