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.