Unexpected epitaxial growth of a few WS₂ Layers on {1100} facets of ZnO nanowires

Core-shell nanowires are an interesting and perspective class of radially heterostructured nanomaterials where epitaxial growth of the shell can be realized even at noticeable core-shell lattice mismatch. In this study epitaxial hexagonally shaped shell consisting of WS₂ nanolayers was grown on {1100} facets of prismatic wurtzite-structured [0001]-oriented ZnO nanowires for the first time. A synthesis was performed by annealing in a sulfur atmosphere of ZnO/WO₃ core-shell structures, produced by reactive dc magnetron sputtering of an amorphous a-WO₃ layer on top of ZnO nanowire array. The morphology and phase composition of synthesized ZnO/WS₂ core-shell nanowires were confirmed by scanning and transmission electron microscopy (SEM and TEM), micro-Raman, and photoluminescence spectroscopy. Epitaxial growth of WS₂(0001) layer(s) on {1100} facets of ZnO nanowire is unexpected due to incompatibility of their symmetry and structure parameters. To relax the interfacial incoherence, we propose a model of ZnO/WS₂ interface containing WS₂ bridging groups inside and use first-principles simulations to support its feasibility.