Ultrafast Dynamics in Single Layer Molybdenum Disulfide
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Authors
Faour, Thomas
Date
2019-09-04
Type
thesis
Language
eng
Keyword
Molybdenum disulfide , MoS2 , Ultrafast dynamics , Single layer , monolayer , 2D Materials , Exciton Dynamics
Alternative Title
Abstract
Molybdenum disulfide, a transition metal dichalcogenide (TMD), has a direct band gap of 1.89 eV when thinned down to a single molecular layer. Exciton recombination pathways and lifetimes have been previously studied, but a consensus has not yet been reached on the physical origins of the reported lifetimes, which range from 2 ps to 10 ns.
We study the excitonic properties of a particular TMD, MoS2. We conduct photoluminescence experiments to characterize the number of layers in our samples, and understand their exciton recombination pathways. We observe PL that is non-linearly dependent on pump fluence, which we attribute to exciton-exciton annihilations. We use a technique that is novel to single layer TMDs, femtosecond excitation correlation spectroscopy (FEC), which exploits the non-linear pump-power dependence. With FEC, we extract exciton-exciton annihilation rates in the high exciton density regime, and a decay rate for lower density regimes. We obtain a low density decay rate of Γ = 0.18 ± 0:02 1/ps, and an exciton-exciton annihilation rate of Γₙₗ = 2.4 ± 0.4 nm²/ps.
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Attribution 3.0 United States
Queen's University's Thesis/Dissertation Non-Exclusive License for Deposit to QSpace and Library and Archives Canada
ProQuest PhD and Master's Theses International Dissemination Agreement
Intellectual Property Guidelines at Queen's University
Copying and Preserving Your Thesis
This publication is made available by the authority of the copyright owner solely for the purpose of private study and research and may not be copied or reproduced except as permitted by the copyright laws without written authority from the copyright owner.
Queen's University's Thesis/Dissertation Non-Exclusive License for Deposit to QSpace and Library and Archives Canada
ProQuest PhD and Master's Theses International Dissemination Agreement
Intellectual Property Guidelines at Queen's University
Copying and Preserving Your Thesis
This publication is made available by the authority of the copyright owner solely for the purpose of private study and research and may not be copied or reproduced except as permitted by the copyright laws without written authority from the copyright owner.