Facile synthesis of two-dimensional MoS2/WS2 lateral heterostructures with controllable core/shell size ratio by a one-step chemical vapor deposition method

Heterostructures based on two-dimensional (2D) transition-metal dichalcogenides (TMDCs) possess unique electronic and optical properties, which open up unprecedented opportunities in nanoscale optoelectronic devices. Synthesizing high-quality 2D TMDC heterostructures with different core/shell size ratios is of great significance for practical applications. Here, we report a simple one-step chemical vapor deposition (CVD) method for fabricating MoS2/WS2 lateral heterostructures with controllable core/shell size ratio. An ultrathin MoO3/WO3 film prepared by thermal evaporation was used as the precursor, and a step-like heating process was adopted to separately grow MoS2 and WS2 monolayers by taking advantage of the different melting points of MoO3 and WO3 sources. High-quality MoS2/WS2 lateral heterostructures with sharp interfaces were fabricated by optimizing the key growth parameters. Furthermore, the core/shell size ratio of heterostructures could be easily controlled by changing the thickness ratio of MoO3/WO3 film, and an approximately linear dependence between them is revealed. Compared with MoS2 or WS2 monolayers, the MoS2/WS2 heterostructure exhibited a shortened exciton lifetime owing to the type-II energy band alignment, which is conducive to the application of high-performance devices. This work provides a facile strategy for the synthesis of 2D lateral heterostructures with controllable size ratio.