Journal
ACS NANO
Volume 8, Issue 10, Pages 10551-10558Publisher
AMER CHEMICAL SOC
DOI: 10.1021/nn503988x
Keywords
transition metal dichalcogenides; molybdenum disulfide; chemical vapor deposition; stoichiometry; photoluminescence; field-effect mobility; X-ray photoelectron spectroscopy
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Funding
- Materials Research Science and Engineering Center (MRSEC) of Northwestern University (National Science Foundation) [DMR-1121262]
- NSF PREM [DMR-0934218]
- Office of Naval Research [N00014-14-1-0669]
- Keck Foundation
- Center for Hierarchical Materials Design (U.S. Department of Commerce) [NIST 70NANB14H012]
- National Center for Research Resources [5 G12RR013646-12]
- National Institute on Minority Health and Health Disparities from the National Institutes of Health [G12MD007591]
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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. The optoelectronic properties of CVD grown monolayer MoS2 have been intensively investigated, but the influence of stoichiometry on the electrical and optical properties has been largely overlooked. Here we systematically vary the stoichiometry of monolayer MoS2 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 MoOx species. As MoS2-d is reduced (increasing d), the field-effect mobility of monolayer transistors increases while the photoluminescence yield becomes nonuniform. Devices fabricated from monolayers with the lowest sulfur content have negligible hysteresis and a threshold voltage of similar to 0 V. We conclude that the electrical and optical properties of monolayer MoS2 crystals can be tuned via stoichiometry engineering to meet the requirements of various applications.
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