Epitaxial growth of In2Se3 on monolayer transition metal dichalcogenide single crystals for high performance photodetectors

One of the most intriguing properties of layered materials is their ability to form inherently ultra-thin atomically sharp vertical interfaces and hybrid layered compounds, in moderate environment conditions, which are ideal platforms for both, scientific research and many applications. Here, we present the selective van der Waals epitaxial formation of β-In2Se3 on transition metal dichalcogenides (TMDCs). This is achieved in a two-step chemical vapor deposition (CVD) process, in which first, the monolayer TMDC, is synthesized and then the β-In2Se3 is grown on top of it. The thickness of the second phase can be controlled by the growth conditions, while the crystal size is dictated by the MoS2 single-crystal domain size. High-resolution transmission electron microscope (HRTEM) studies reveal a clean and sharp interface, while selected area diffraction (SAED) demonstrates a clear registry between both phases. The hybrid layered-compound exhibit better electrical transport than the intrinsic indium-selenide layer. The high crystallinity of In2Se3 grown on MoS2 yield fast response among the CVD-derived In2Se3-based photodetectors with rise/fall times of 4/7 ms, photoresponsivity of up to ~23 A/W and specific detectivity of ~ 5 × 1011. Our methodology allows high quality thin In2Se3 layers to be formed via van der Waals epitaxy on TMDCs, forming complex vertical heterostructures for optoelectronic applications.