Enhancing Photoluminescence and Mobilities in WS2 Monolayers with Oleic Acid Ligands.
Authors
Delport, Géraud
Gauriot, Nicolas
Li, Zhaojun
Publication Date
2019-09-11Journal Title
Nano Letters: a journal dedicated to nanoscience and nanotechnology
ISSN
1530-6984
Publisher
American Chemical Society
Volume
19
Issue
9
Pages
6299-6307
Language
eng
Type
Article
This Version
VoR
Metadata
Show full item recordCitation
Tanoh, A., Alexander-Webber, J., Xiao, J., Delport, G., Williams, C., Bretscher, H., Gauriot, N., et al. (2019). Enhancing Photoluminescence and Mobilities in WS2 Monolayers with Oleic Acid Ligands.. Nano Letters: a journal dedicated to nanoscience and nanotechnology, 19 (9), 6299-6307. https://doi.org/10.1021/acs.nanolett.9b02431
Abstract
Many potential applications of monolayer transition metal dichalcogenides (TMDs) require both high photoluminescence (PL) yield and high electrical mobilities. However, the PL yield of as prepared TMD monolayers is low and believed to be limited by defect sites and uncontrolled doping. This has led to a large effort to develop chemical passivation methods to improve PL and mobilities. The most successful of these treatments is based on the nonoxidizing organic "superacid" bis(trifluoromethane)sulfonimide (TFSI) which has been shown to yield bright monolayers of molybdenum disulfide (MoS2) and tungsten disulfide (WS2) but with trap-limited PL dynamics and no significant improvements in field effect mobilities. Here, using steady-state and time-resolved PL microscopy we demonstrate that treatment of WS2 monolayers with oleic acid (OA) can greatly enhance the PL yield, resulting in bright neutral exciton emission comparable to TFSI treated monolayers. At high excitation densities, the OA treatment allows for bright trion emission, which has not been demonstrated with previous chemical treatments. We show that unlike the TFSI treatment, the OA yields PL dynamics that are largely trap free. In addition, field effect transistors show an increase in mobilities with the OA treatment. These results suggest that OA serves to passivate defect sites in the WS2 monolayers in a manner akin to the passivation of colloidal quantum dots with OA ligands. Our results open up a new pathway to passivate and tune defects in monolayer TMDs using simple "wet" chemistry techniques, allowing for trap-free electronic properties and bright neutral exciton and trion emission.
Keywords
Tungsten disulfide, ligand passivation, mobilities, photoluminescence
Sponsorship
Engineering and Physical Sciences Research Council (EP/M006360/1)
Engineering and Physical Sciences Research Council (EP/P027741/1)
EPSRC (1648003)
European Research Council (758826)
EPSRC (1648003)
Engineering and Physical Sciences Research Council (EP/L016087/1)
Engineering and Physical Sciences Research Council (EP/L015978/1)
Engineering and Physical Sciences Research Council (EP/P005152/1)
European Research Council (756962)
EPSRC (1948696)
Embargo Lift Date
2100-01-01
Identifiers
External DOI: https://doi.org/10.1021/acs.nanolett.9b02431
This record's URL: https://www.repository.cam.ac.uk/handle/1810/295998
Rights
Attribution 4.0 International (CC BY)
Licence URL: http://creativecommons.org/licenses/by/4.0/
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