Anisotropic Growth of Nonlayered CdS on MoS2 Monolayer for Functional Vertical Heterostructures

2D semiconductors have emerged as a crucial material for use in next-generation optotelectronics. Similar to microelectronic devices, 2D vertical heterostructures will most likely be the elemental components for future nanoscale electronics and optotelectronics. To date, the components of mostly reported 2D van der Waals heterostructures are restricted to layer crystals. In this work, it is demonstrated that nonlayered semiconductors of CdS can be epitaxially grown on to 2D layered MoS2 substrate to form a new quasi vertical heterostructure with clean interface by chemical vapor deposition. Photodetectors based on this CdS/MoS2 heterostructure show broader wavelength response and similar or equal to 50-fold improvement in photoresponsivity, compared to the devices fabricated from MoS2 monolayer only. This research opens up a way to fabricate a variety of functional quasi heterostructures from nonlayered semiconductors.