2013
DOI: 10.1103/physrevb.88.115313
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Anomalous quantum confinement of the longitudinal optical phonon mode in PbSe quantum dots

Abstract: We have investigated the diameter dependence of the Raman spectra of lead selenide nanocrystals. The first-order Raman peak at about 136 cm −1 and its second-order overtone at twice this wavenumber move up in energy with decreasing nanocrystal diameter. This anomalous behavior is interpreted in terms of quantum confinement of the longitudinal optical (LO) phonon whose frequency displays a minimum at in the dispersion of bulk PbSe. We perform ab initio calculations of the phonons of PbSe slabs with up to 15 lay… Show more

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Cited by 23 publications
(13 citation statements)
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“…In addition, the Raman spectra show a SP mode that is stronger for the sample that was grown at 400 ○ C. This mode belongs to the Pb-O-Pb stretching mode at the surface of the nanocrystals. 27 Therefore, the Raman results also confirm that the obtained nanostructures are PbSe.…”
supporting
confidence: 74%
“…In addition, the Raman spectra show a SP mode that is stronger for the sample that was grown at 400 ○ C. This mode belongs to the Pb-O-Pb stretching mode at the surface of the nanocrystals. 27 Therefore, the Raman results also confirm that the obtained nanostructures are PbSe.…”
supporting
confidence: 74%
“…These data allow deriving standard characteristics of the QDs by employing semi‐empirical expressions . We find a temperature coefficient d E g ′/d T = (120 ± 9) μeV K −1 , and Debye temperature of (101 ± 19) K. The longitudinal optical (LO) phonon energy (18.6 ± 2.6) meV is consistent with reports, but falls below the value of (29.6 ± 0.8) meV obtained from the FWHM(T) evolution. The Arrhenius plot of the PL line points to an activation energy of 16.5 meV, see inset in Figure b, which matches the LO phonon energy obtained from the E g ′(T) evolution.…”
supporting
confidence: 81%
“…However, Raman spectra obtained for the PbSe QDs of the same size, synthesized by cation-exchange and direct hot-injection methods, demonstrate similar behavior. The positions of phonon peaks were determined and compared to the known literature data [ 73 , 74 , 75 , 76 ]. The positions of the typical phonon peaks (LA(X), 2TA(X), LO(X) and/or LA(X)/TA(X), 2TO(X), and LO(Γ)) are close for both types of QDs and PbSe NPLs (see Table S1 , Supplementary Materials ).…”
Section: Discussionmentioning
confidence: 99%