Growth of Highly Oriented (VNbMoTaW)S<sub>2</sub> Layers.

Tanaka, Koichi; Zaid, Hicham; Aoki, Toshihiro; Deshpande, Aditya; Hojo, Koki; Ciobanu, Cristian V; Kodambaka, Suneel · Nano Lett · 2024

basic_science · Level V

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Abstract

Compositional tunability, an indispensable parameter for modifying the properties of materials, can open up new applications for van der Waals (vdW) layered materials such as transition-metal dichalcogenides (TMDCs). To date, multielement alloy TMDC layers are obtained via exfoliation from bulk polycrystalline powders. Here, we demonstrate direct deposition of high-entropy alloy disulfide, (VNbMoTaW)S<sub>2</sub>, layers with controllable thicknesses on free-standing graphene membranes and on bare and hBN-covered Al<sub>2</sub>O<sub>3</sub>(0001) substrates via ultra-high-vacuum reactive dc magnetron sputtering of the VNbMoTaW target in Kr and H<sub>2</sub>S gas mixtures. Using a combination of density functional theory calculations, Raman spectroscopy, X-ray diffraction, scanning transmission electron microscopy coupled with energy dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy, we determine that the as-deposited layers are single-phase, 2H-structured, and 0001-oriented (V<sub>0.10</sub>Nb<sub>0.16</sub>Mo<sub>0.19</sub>Ta<sub>0.28</sub>W<sub>0.27</sub>)S<sub>2.44</sub>. Our synthesis route is general and applicable for heteroepitaxial growth of a wide variety of TMDC alloys and potentially other multielement alloy vdW compounds with the desired compositions.