General synthesis of mixed-dimensional van der Waals heterostructures with hexagonal symmetry

Abstract The combination of two-dimensional (2D) materials with non-2D materials (quantum dots, nanowires and bulk materials), i.e. mixed-dimensional van der Waals (md-vdW) heterostructures endow 2D materials with remarkable electronics properties. However, it remains a big challenge to synthesize md-vdW heterostructures because of the difference of crystal symmetry between 2D and non-2D materials. Meanwhile, it is difficult to initiate the nucleation due to the lack of chemical active sites on chemical inert surfaces of 2D materials. Herein, we design a general chemical vapor deposition method for synthesizing a broad class of md-vdW heterostructures with well-aligned hexagonal symmetry including MoS ₂ /FeS, MoS ₂ /CoS, MoS ₂ /MnS, MoS ₂ /ZnS, Mo(S _x Se _{1– x} ) ₂ /ZnS _x Se _{1– x} , Mo(S _x Se _{1– x} ) ₂ /CdS _x Se _{1– x} . Combining with DFT calculation, we find that the hexagonal symmetry and the centered clusters of MoS ₂ and Mo(S _x Se _{1– x} ) ₂ nanoflakes are two crucial factors to launch the hexagonally oriented growth and nucleation of non-2D materials on 2D materials. Our discovery opens an opportunity for the versatile hetero-integration of 2D materials and allows systematic investigation of physical properties in a wide variety of md-vdW heterostructures.