Growth of Highly Oriented (VNbMoTaW)S 2 Layers.

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 2 , layers with controllable thicknesses on free-standing graphene membranes and on bare and hBN-covered Al 2 O 3 (0001) substrates via ultra-high-vacuum reactive dc magnetron sputtering of the VNbMoTaW target in Kr and H 2 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 0.10 Nb 0.16 Mo 0.19 Ta 0.28 W 0.27 )S 2.44 . 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.