15 October 2012 Low-temperature photocarrier dynamics in single-layer MoS2 flakes
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Proceedings Volume 8456, Nanophotonic Materials IX; 84560H (2012); doi: 10.1117/12.928067
Event: SPIE NanoScience + Engineering, 2012, San Diego, California, United States
Abstract
The dichalcogenide MoS2, which is an indirect-gap semiconductor in its bulk form, was recently shown to become an efficient emitter of photoluminescence as it is thinned to a single layer, indicating a transition to a direct-gap semiconductor due to confinement effects. With its layered structure of weakly coupled, covalently bonded two-dimensional sheets, it can be prepared, just as graphene, using mechanical exfoliation techniques. Here, we present temperature-dependent and time-resolved photoluminescence (PL) studies of single-layer MoS2 flakes. Some of the flakes are covered with oxide layers prepared by atomic layer deposition (ALD). At low temperatures, we clearly see two PL peaks in the as-prepared flakes without oxide layers, which we may assign to bound and free exciton transitions. The lower-energy, bound exciton PL peak is absent in the oxide-covered flakes. In time-resolved PL measurements, we observe very fast photocarrier recombination on the few-ps timescale at low temperatures, with increasing photocarrier lifetimes at higher temperatures due to exciton-phonon scattering.
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T. Korn, G. Plechinger, S. Heydrich, M. Hirmer, F.-X. Schrettenbrunner, D. Weiss, J. Eroms, C. Schüller, "Low-temperature photocarrier dynamics in single-layer MoS2 flakes", Proc. SPIE 8456, Nanophotonic Materials IX, 84560H (15 October 2012); doi: 10.1117/12.928067; https://doi.org/10.1117/12.928067
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KEYWORDS
Excitons

Temperature metrology

Luminescence

Oxides

Atomic layer deposition

Picosecond phenomena

Semiconductors

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