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Giant Photoluminescence Enhancement in MoSe2 Monolayers treated with Oleic Acid Ligands

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Peer-reviewed

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Authors

Gauriot, Nicolas 
Pandya, R 
Alexander-Webber, Jack  ORCID logo  https://orcid.org/0000-0002-9374-7423

Abstract

The inherently low photoluminescence (PL) yields in as prepared transition metal dichalcogenide (TMD) monolayers are broadly accepted to be the result of atomic vacancies (i.e., defects) and uncontrolled doping, which give rise to non-radiative exciton decay pathways. To date, a number of chemical passivation schemes have been successfully developed to improve PL in sulphur based TMDs i.e., molybdenum disulphide (MoS2) and tungsten disulphide (WS2) monolayers. Studies on solution based chemical passivation schemes for improving PL yields in selenium (Se) based TMDs are however lacking in comparison. Here, we demonstrate that treatment with oleic acid (OA) provides a simple wet chemical passivation method for monolayer MoSe2, enhancing PL yield by an average of 58-fold, while also improving spectral uniformity across the material and reducing emission linewidth. Excitation intensity dependent PL reveals trap-free PL dynamics dominated by neutral exciton recombination. Time-resolved PL (TRPL) studies reveal significantly increased PL lifetimes, with pump intensity dependent TRPL measurements also confirming trap free PL dynamics in OA treated MoSe2. Field effect transistors show reduced charge trap density and improved on-off ratios after treatment with OA. These results indicate defect passivation by OA, which we hypothesise act as ligands, passivating chalcogen defects through oleate coordination to Mo dangling bonds. Importantly, this work combined with our previous study by on OA treated WS2,1 verifies OA treatment as a simple solution-based chemical passivation protocol for improving PL yields and electronic characteristics in both selenide and sulphide TMDs- a property that has not been reported previously for other solution- based passivation schemes.

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Journal Title

Nanoscale Advances

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Journal ISSN

2516-0230

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Publisher

Royal Society of Chemistry

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All rights reserved
Sponsorship
Engineering and Physical Sciences Research Council (EP/M006360/1)
Engineering and Physical Sciences Research Council (EP/P027741/1)
European Research Council (758826)
EPSRC (1948696)
EPSRC (1648003)
EPSRC (1648003)
Engineering and Physical Sciences Research Council (EP/P005152/1)
Royal Commission for the Exhibition of 1851 (RF474/2016)
Royal Society (DHF\F1\191163)
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