Synthesis and Characterization of Quaternary Monolayer Thick MoSe₂/SnSe/NbSe₂/SnSe Heterojunction Superlattices

The synthesis of multiple-component heterostructures is conventionally accomplished through mechanical or chemical exfoliation, followed by physically stacking the layers together. Here, we report the synthesis, structure, and local composition of a three-component heterostructure (SnSe) 1.16 (MoSe 2 ) 1.06 (SnSe) 1.16 (NbSe 2 ) 1, which was self-assembled at relatively low temperature (450 °C) from a designed precursor. XRD and STEM studies showed that the compound consisted of alternating layers of trigonal prismatic MoSe 2 and NbSe 2, interleaved with SnSe layers in a distorted rock salt structure. The new three-component ferecrystal is metallic with a factor of 3 higher conductivity than the (SnSe) 1+δ (Nb x Mo 1– x )Se 2 ferecrystal alloy of the same composition ( x ≈ 0.5). Comparison of the in-plane lattice parameters with the (SnSe) 1+δ (Nb x Mo 1− x )Se 2 alloys allowed the extent of interdiffusion of the dichalcogenide constituents to be evaluated, yielding a stoichiometry of (SnSe) 1.16 ([Mo 0.9 Nb 0.1 ]Se 2 ) 1.06 (SnSe) 1.16 ([Nb 0.9 Mo 0.1 ]Se 2 ) 1 .