Tailoring Domain Morphology in Monolayer NbSe2 and WxNb1–xSe2 Heterostructure

Abstract

Copyright © 2020 American Chemical Society Domain morphology plays a pivotal role not only for the synthesis of high-quality 2D transition metal dichalcogenides (TMDs) but also for the further unveiling of related physical and chemical properties, yet little has been divulged to date, especially for metallic TMDs. In addition, solid precursor as a transition metal source has been conventionally introduced for the synthesis of TMDs, which leads to an inhomogeneous distribution of local domains with the substrate position, making it difficult to obtain a reliable film. Here, we tailor the domain morphologies of metallic NbSe2 and NbSe2/WSe2 heterostructures using liquid-precursor chemical vapor deposition (CVD). We find that triangular, hexagonal, tripod-like, and herringbone-like NbSe2 flakes are constructed through control of growth temperature and promoter and precursor concentration. Liquid-precursor CVD ensures domain morphologies that are highly reproducible over repeated growth and uniform along the gas-flow direction. A domain coverage of ∼80% is achieved at a high precursor concentration, starting with tripod-like NbSe2 domain and evolving to the herringbone fractal. Furthermore, mixing liquid W and Nb precursors results in sea-urchin-like heterostructure domains with long-branch-shaped NbSe2 at low temperature, whereas protruded hexagonal heterostructure domains grow at high temperature. Our liquid precursor approach provides a shortcut for tailoring the domain morphologies of metallic TMDs as well as metal/semiconductor heterostructures.