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

Autor: Klots AR; Department of Physics and Astronomy, Vanderbilt University, Nashville, TN-37235, USA., Newaz AK; Department of Physics and Astronomy, Vanderbilt University, Nashville, TN-37235, USA., Wang B; Department of Physics and Astronomy, Vanderbilt University, Nashville, TN-37235, USA., Prasai D; Interdisciplinary Graduate Program in Materials Science, Vanderbilt University, Nashville, TN-37234, USA., Krzyzanowska H; Department of Physics and Astronomy, Vanderbilt University, Nashville, TN-37235, USA., Lin J; 1] Department of Physics and Astronomy, Vanderbilt University, Nashville, TN-37235, USA [2] Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN-37831, USA., Caudel D; Department of Physics and Astronomy, Vanderbilt University, Nashville, TN-37235, USA., Ghimire NJ; 1] Department of Physics and Astronomy, University of Tennessee, Knoxville, TN-37996, USA [2] Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN-37831, USA., Yan J; 1] Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN-37831, USA [2] Department of Materials Science and Engineering, University of Tennessee, Knoxville, TN-37996, USA., Ivanov BL; Department of Physics and Astronomy, Vanderbilt University, Nashville, TN-37235, USA., Velizhanin KA; Theoretical Division, Los Alamos National Laboratory, Los Alamos, NM-87545, USA., Burger A; Department of Physics, Fisk University, Nashville, TN-37208, USA., Mandrus DG; 1] Department of Physics and Astronomy, University of Tennessee, Knoxville, TN-37996, USA [2] Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN-37831, USA [3] Department of Materials Science and Engineering, University of Tennessee, Knoxville, TN-37996, USA., Tolk NH; Department of Physics and Astronomy, Vanderbilt University, Nashville, TN-37235, USA., Pantelides ST; 1] Department of Physics and Astronomy, Vanderbilt University, Nashville, TN-37235, USA [2] Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN-37831, USA., Bolotin KI; Department of Physics and Astronomy, Vanderbilt University, Nashville, TN-37235, USA.
Jazyk: angličtina
Zdroj: Scientific reports [Sci Rep] 2014 Oct 16; Vol. 4, pp. 6608. Date of Electronic Publication: 2014 Oct 16.
DOI: 10.1038/srep06608
Abstrakt: 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.
Databáze: MEDLINE
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