Influence of Stoichiometry on the Optical and Electrical Properties of Chemical Vapor Deposition Derived MoS${}_2$

Abstract

Ultrathin transition metal dichalcogenides (TMDCs) of Mo and W show great potential for digital electronics and optoelectronic applications. Whereas early studies were limited to mechanically exfoliated flakes, the large-area synthesis of 2D TMDCs has now been realized by chemical vapor deposition (CVD) based on a sulfurization reaction. Since then, the optoelectronic properties of CVD grown monolayer MoS${}_2$ have been heavily investigated, but the influence of stoichiometry on the electrical and optical properties has been largely overlooked. Here we systematically vary the stoichiometry of monolayer MoS${}_2$ during CVD via controlled sulfurization and investigate the associated changes in photoluminescence and electrical properties. X-ray photoelectron spectroscopy is employed to measure relative variations in stoichiometry and the persistence of MoO${}_x$ species. As MoS${}_{2-\delta }$ is reduced (increasing δ), the field-effect mobility of monolayer transistors increases while the photoluminescence yield becomes non-uniform. Devices fabricated from monolayers with the lowest sulfur content have negligible hysteresis and a threshold voltage of ~0 V. We conclude that the electrical and optical properties of monolayer MoS${}_2$ crystals can be tuned via stoichiometry engineering to meet the requirements of various applications.

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• Interface Dipole and Band Bending in Hybrid p-n Heterojunction MoS2/GaN(0001)
• Roadmap for Photonics with 2D Materials
• Growth-Induced Strain in Chemical Vapor Deposited Monolayer MoS2: Experimental and Theoretical Investigation
• Tuning Conductivity Type in Monolayer WS2 and MoS2 by Sulfur Vacancies
• NaCl-assisted CVD growth of wafer scale high quality trilayer MoS${}_2$ and the role of concentration boundary layer
• Large-Area Transfer of 2D TMDCs Assisted by Water-soluble layer for Potential Device Applications
• Effects of CVD Growth Parameters on Global and Local Optical Properties of MoS${}_2$ Monolayers
• High Throughput Characterization of Epitaxially Grown Single-Layer MoS2
• Multi-terminal electronic transport in boron nitride encapsulated TiS${}_3$ nanosheets
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