Growth of Highly Oriented (VNbMoTaW)S<sub>2</sub> Layers
Kōichi Tanaka, Hicham Zaid, Toshihiro Aoki, Aditya Deshpande, Koki Hojo, Cristian V. Ciobanu, Suneel Kodambaka
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 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.