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Probing excitonic states in suspended two-dimensional semiconductors by photocurrent spectroscopy

Klots, A R ; Newaz, A K M ; Wang, Bin ; Prasai, D ; Krzyzanowska, H ; Lin, Junhao ; Caudel, D ; Ghimire, N J ; Yan, J ; Ivanov, B L ; Velizhanin, K A ; Burger, A ; Mandrus, D G ; Tolk, N H ; Pantelides, S T ; Bolotin, K I

Scientific reports, 2014-10, Vol.4 (1), p.6608-6608, Article 6608 [Periódico revisado por pares]

England: Nature Publishing Group

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  • Título:
    Probing excitonic states in suspended two-dimensional semiconductors by photocurrent spectroscopy
  • Autor: Klots, A R ; Newaz, A K M ; Wang, Bin ; Prasai, D ; Krzyzanowska, H ; Lin, Junhao ; Caudel, D ; Ghimire, N J ; Yan, J ; Ivanov, B L ; Velizhanin, K A ; Burger, A ; Mandrus, D G ; Tolk, N H ; Pantelides, S T ; Bolotin, K I
  • Assuntos: Electronic properties and materials ; MATERIALS SCIENCE ; Nanoscience and technology ; Nanosensors ; Photoresponse ; Spectroscopy ; Spectrum analysis ; Splitting ; Temperature effects ; Thermodynamics ; Two-dimensional materials
  • É parte de: Scientific reports, 2014-10, Vol.4 (1), p.6608-6608, Article 6608
  • Notas: ObjectType-Article-1
    SourceType-Scholarly Journals-1
    ObjectType-Feature-2
    content type line 23
    USDOE Office of Science (SC), Basic Energy Sciences (BES)
    FGO2-99ER45781; W911NF-07-R-0003-02; NSF ARI-R2 DMR-0963361; NSF EPS1004083; ONR- N000141310299; NSF CAREER DMR-1056859; HDTRA1-10-0047; AC05-00OR22725
    These authors contributed equally to this work.
    Current address: Department of Physics and Astronomy, San Francisco State University, San Francisco, CA-94132, USA.
    Current address: Department of Chemical, Biological & Materials Engineering, University of Oklahoma, Norman, OK 73019.
  • Descrição: The optical response of semiconducting monolayer transition-metal dichalcogenides (TMDCs) is dominated by strongly bound excitons that are stable even at room temperature. However, substrate-related effects such as screening and disorder in currently available specimens mask many anticipated physical phenomena and limit device applications of TMDCs. Here, we demonstrate that that these undesirable effects are strongly suppressed in suspended devices. Extremely robust (photogain > 1,000) and fast (response time < 1 ms) photoresponse allow us to study, for the first time, the formation, binding energies, and dissociation mechanisms of excitons in TMDCs through photocurrent spectroscopy. By analyzing the spectral positions of peaks in the photocurrent and by comparing them with first-principles calculations, we obtain binding energies, band gaps and spin-orbit splitting in monolayer TMDCs. For monolayer MoS2, in particular, we obtain an extremely large binding energy for band-edge excitons, E bind ≥ 570 meV. Along with band-edge excitons, we observe excitons associated with a van Hove singularity of rather unique nature. The analysis of the source-drain voltage dependence of photocurrent spectra reveals exciton dissociation and photoconversion mechanisms in TMDCs.
  • Editor: England: Nature Publishing Group
  • Idioma: Inglês
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