Scrolling bilayer WS₂/MoS₂ heterostructures for high-performance photo-detection

Recently, transition metal dichalcogenides (TMDCs) nanoscrolls have exhibited unique electronic and optical properties due to their spiral tubular structures, which are formed by rolling up monolayer TMDCs nanosheets. Inspired by the excellent physical and chemical properties of TMDCs van der Waals heterostructures (vdWHs), it is highly desirable to scroll TMDCs vdWHs for potential optoelectronic applications. In this work, WS₂/MoS₂ vdWHs nanoscrolls were massively prepared by dropping aqueous alkaline droplet on chemical vapor deposition (CVD)-grown bilayer WS₂/MoS₂ vdWHs, which were formed by growing monolayer WS₂ islands on top of monolayer MoS₂ nanosheets simultaneously. The optical microscopy (OM), atomic force microscopy (AFM), ultralow frequency (ULF) Raman spectroscopy and transmission electron microscopy (TEM) were utilized to characterize the WS₂/MoS₂ vdWHs nanoscrolls. As-obtained WS₂/MoS₂ vdWHs nanoscrolls exhibited new ULF breathing mode as well as shear mode peaks due to the strong interlayer interaction. Notably, the photosensitivities of WS₂/MoS₂ vdWHs nanoscrolls-based devices were about ten times higher than those of WS₂/MoS₂ vdWHs-based devices under blue, green and red lasers, respectively, which could be attributed to the ultrafast charge transfer at alternative WS₂/MoS₂ and MoS₂/WS₂ multi-interfaces in scrolled structure. Our work suggested that TMDCs vdWHs scrolls could be promising candidates for optoelectronic applications.