Direct van der Waals epitaxial growth of 1D/2D Sb₂Se₃/WS₂ mixed-dimensional p-n heterojunctions

The mixed-dimensional integration of two-dimensional (2D) materials with non-2D materials can give rise to prominent advances in performance or function. To date, the mixed-dimensional one-dimensional (1D)/2D heterostructures have been fabricated using various physical assembly approaches. However, direct epitaxial growth method which has notable advantages in preparing large-scale products and obtaining perfect interfaces is rarely investigated. Herein, we demonstrate for the first time the direct synthesis of the 1D/2D mixed-dimensional heterostructures by sequential vapor-phase growth of Sb₂Se₃ nanowires on WS₂ monolayers. X-ray diffraction (XRD) pattern and Raman spectrum confirm the composition of the Sb₂Se₃/WS₂ heterostructures. Transmission electron microscope (TEM) measurement demonstrates high quality of the heterostructures. Electrical transport characterization reveals that Sb₂Se₃ nanowire exhibits p-type characteristic and that WS₂ monolayer exhibits n-type behavior, and that the p-n diode from 1D/2D mixed-dimensional Sb₂Se₃/WS₂ heterostructure possesses obvious current rectification behavior. Optoelectronic measurements of the heterostructures show apparent photovoltaic response with an open-circuit voltage of 0.19 V, photoresponsivity of 1.51 A/W (V_ds = 5 V) and fast response time of less than 8 ms. The van der Waals epitaxial growth mode of Sb₂Se₃ nanowires on WS₂ monolayers is verified by stripping the Sb₂Se₃ nanowire from the heterostructures using tape. Together, the direct van der Waals epitaxy opens a facile pathway to 1D/2D mixed-dimensional heterostructures for functional electronic and optoelectronic devices.