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Disentangling oxygen and water vapor effects on optoelectronic properties of monolayer tungsten disulfide

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Title
Disentangling oxygen and water vapor effects on optoelectronic properties of monolayer tungsten disulfide
Author(s)
Hanyu Zhang; Jeremy R. Dunklin; Obadiah G. Reid; Seok Joon Yun; Sanjini U. Nanayakkara; Young Hee Lee; Jeffrey L. Blackburn; Elisa M. Miller
Subject
TRANSITION-METAL DICHALCOGENIDES, ; CHARGE-CARRIERS, ; RAMAN-SPECTROSCOPY, ; LIGHT-EMISSION, ; LAYER MOS2, ; PHOTOLUMINESCENCE, ; WS2, ; NANOSHEETS, ; MONO, ; EXCITONS
Publication Date
2020-04
Journal
NANOSCALE, v.12, no.15, pp.8344 - 8354
Publisher
ROYAL SOC CHEMISTRY
Abstract
© The Royal Society of Chemistry 2020, By understanding how the environmental composition impacts the optoelectronic properties of transition metal dichalcogenide monolayers, we demonstrate that simple photoluminescence (PL) measurements of tungsten disulfide (WS2) monolayers can differentiate relative humidity environments. In this paper, we examine the PL and photoconductivity of chemical vapor deposition grown WS2 monolayers under three carefully controlled environments: inert gas (N-2), dry air (O-2 in N-2), and humid nitrogen (H2O vapor in N-2). The WS2 PL is measured as a function of 532 nm laser power and exposure time and can be decomposed into the exciton, trion, and lower energy state(s) contributions. Under continuous illumination in either O-2 or H2O vapor environment, we find dramatic (and reversible) increases in PL intensity relative to the PL in an inert environment. The PL bathochromically shifts in an O-2 environment and is dominated by increased trion emission and diminished exciton emission. In contrast, the WS2 PL increase in a H2O environment results from an overall increase in emission from all spectral components where the exciton contribution dominates. The drastic increases in PL are anticorrelated with corresponding decreases in photoconductivity, as measured by time-resolved microwave conductivity. The results suggest that both O-2 and H2O react photochemically with the WS2 monolayer surface, modifying the optoelectronic properties, but do so via distinct pathways. Thus, we use these optoelectronic differences to differentiate the amount of humidity in the air, which we show with 0%, 40%, and 80% relative humidity environments. This deeper understanding of how ambient conditions impact WS2 monolayers enables novel humidity sensors as well as a better understanding of the correlation between TMDC surface chemistry, light emission, and photoconductivity. Moreover, these WS2 measurements highlight the importance of considering the impact of the local environment on reported results
URI
https://pr.ibs.re.kr/handle/8788114/8658
DOI
10.1039/c9nr09326e
ISSN
2040-3364
Appears in Collections:
Center for Integrated Nanostructure Physics(나노구조물리 연구단) > 1. Journal Papers (저널논문)
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