Second-Order Raman Scattering in Exfoliated Black Phosphorus

Second-order Raman scattering has been extensively studied in carbon-based nanomaterials, for example, nanotube and graphene, because it activates normally forbidden Raman modes that are sensitive to crystal disorder, such as defects, dopants, strain, and so forth. The sp2-hybridized carbon systems...

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Veröffentlicht in:Nano letters Jg. 18; H. 2; S. 1018 - 1027
Hauptverfasser: Favron, Alexandre, Goudreault, Félix Antoine, Gosselin, Vincent, Groulx, Julien, Côté, Michel, Leonelli, Richard, Germain, Jean-Francis, Phaneuf-L’Heureux, Anne-Laurence, Francoeur, Sébastien, Martel, Richard
Format: Journal Article
Sprache:Englisch
Veröffentlicht: United States American Chemical Society 14.02.2018
Schlagworte:
doubly resonant Raman
phonon-defect modes
anisotropic properties
Black phosphorus
ISSN:1530-6984, 1530-6992, 1530-6992
Online-Zugang:Volltext
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Zusammenfassung:Second-order Raman scattering has been extensively studied in carbon-based nanomaterials, for example, nanotube and graphene, because it activates normally forbidden Raman modes that are sensitive to crystal disorder, such as defects, dopants, strain, and so forth. The sp2-hybridized carbon systems are, however, the exception among nanomaterials, where first-order Raman processes usually dominate. Here we report the identification of four second-order Raman modes, named D1, D1 ′, D2 and D2 ′, in exfoliated black phosphorus (P­(black)), an elemental direct-gap semiconductor exhibiting strong mechanical and electronic anisotropies. Located in close proximity to the Ag 1 and Ag 2 modes, these new modes dominate at an excitation wavelength of 633 nm. Their evolutions as a function of sample thickness, excitation wavelength, and defect density indicate that they are defect-activated and involve high-momentum phonons in a doubly resonant Raman process. Ab initio simulations of a monolayer reveal that the D′ and D modes occur through intravalley scatterings with split contributions in the armchair and zigzag directions, respectively. The high sensitivity of these D modes to disorder helps explaining several discrepancies found in the literature.
Bibliographie:ObjectType-Article-1
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ISSN:1530-6984
1530-6992
1530-6992
DOI:10.1021/acs.nanolett.7b04486