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Aging of Transition Metal Dichalcogenide Monolayers
journal contribution
posted on 2016-01-25, 00:00 authored by Jian Gao, Baichang Li, Jiawei Tan, Phil Chow, Toh-Ming Lu, Nikhil KoratkarTwo-dimensional
sheets of transition metal dichalcogenides are an emerging class of
atomically thin semiconductors that are considered to be “air-stable”,
similar to graphene. Here we report that, contrary to current understanding,
chemical vapor deposited transition metal dichalcogenide monolayers
exhibit poor long-term stability in air. After room-temperature exposure
to the environment for several months, monolayers of molybdenum disulfide
and tungsten disulfide undergo dramatic aging effects including extensive
cracking, changes in morphology, and severe quenching of the direct
gap photoluminescence. X-ray photoelectron and Auger electron spectroscopy
reveal that this effect is related to gradual oxidation along the
grain boundaries and the adsorption of organic contaminants. These
results highlight important challenges associated with the utilization
of transition metal dichalcogenide monolayers in electronic and optoelectronic
devices. We also demonstrate a potential solution to this problem,
featuring encapsulation of the monolayer sheet by a 10–20 nm
thick optically transparent polymer (parylene C). This strategy is
shown to successfully prevent the degradation of the monolayer material
under accelerated aging (i.e., high-temperature,
oxygen-rich) conditions.
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- Biophysics
- Physical Sciences not elsewhere classified
- Genetics
- Molecular Biology
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Keywords
monolayer materialmolybdenum disulfidetransition metal dichalcogenide monolayerstransition metal dichalcogenidesparylene Cchemical vaportungsten disulfidegrain boundariestransition metal dichalcogenide monolayers exhibitgap photoluminescenceAuger electron spectroscopymonolayer sheetoptoelectronic devices
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