Positive and Negative Photoconductivity in Monolayer MoS₂ as a Function of Physisorbed Oxygen
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Date
2021-04-16
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Citation of Original Publication
Gustafson, Jon K. et al. Positive and Negative Photoconductivity in Monolayer MoS2 as a Function of Physisorbed Oxygen. The Journal of Physical Chemistry C 2021 125 (16), 8712-8718 DOI: 10.1021/acs.jpcc.1c01550
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This document is the unedited Author’s version of a Submitted Work that was subsequently accepted for publication in The Journal of Physical Chemistry C , copyright © American Chemical Society after peer review. To access the final edited and published work see https://doi.org/10.1021/acs.jpcc.1c01550
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Abstract
We investigate the effect of molecular oxygen on the photoconductivity of monolayer
MoS₂ via broad-band time-resolved terahertz spectroscopy. We observe that the
photoconductivity of monolayer MoS₂ transitions from negative to positive when the
environment of MoS₂ changes from vacuum to atmospheric pressure. We argue that this
transition from negative to positive photoconductivity results from physically adsorbed oxygen
depleting excess electrons from the n-type MoS₂. We attribute the negative photoconductivity to
negative trion formation, in which photoinduced excitons capture excess electrons from the
MoS₂. We attribute the positive photoconductivity to negative trion formation as well; however,
in this case, photoinduced excitons capture photoinduced defect electrons rather than excess
electrons, which have been immobilized by physisorbed oxygen. These results should prove
useful to those who look to make sensors and other types of devices out of monolayer MoS₂ as
physisorbed gases, particularly oxygen, can dramatically affect the conductivity of the
monolayer.