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Author: Andy G Barrette
Requested Type: Poster
Submitted: 2015-04-15 14:33:26

Co-authors: Chao Xu, Yifei Yu, Yiling Yu, Linyou Cao, Kenan Gundogdu

Contact Info:
Andy Barrette
851 Main Campus Drive
Raleigh, NC   27695
United States

Abstract Text:
Atomically thin transition metal dichalcogenides exhibit exotic optical and electronic properties that do not exist in bulk materials. For instance in MoS2 spin and valley degrees of freedom are coupled and therefore one can control carrier population in specific valleys using circularly polarized light. This property could be the base for potential spintronic/valleytronic applications, which would require low spin/valley relaxation rates. Because these materials are either exfoliated or grown on other substrates, 2D material/substrate interactions can have a significant impact on excitation relaxation and recombination dynamics. In this work we studied exciton lifetime and valley relaxation time of MoS2 on various substrates using ultrafast transient absorption spectroscopy. Dependence of relaxation time on pump fluence allows us to monitor saturation of defects available for defect-bound exciton formation. We found that carriers do relax via defects within the 2D material and also scatter into the substrate on ultrafast time scales. Our results elucidate the extent of interactions between excitons in a single MoS2 layer and defects in the layer and substrate. This result may guide the design of viable nano-scale electronic and spintronic devices in the future.