Anomalous quantum confinement of the longitudinal optical phonon mode in PbSe quantum dots
English
Habinshuti, J.[Institut d’Electronique, de Microélectronique et de Nanotechnologie (IEMN), CNRS ; Laboratoire de Spectrochimie Infrarouge et Raman, LASIR, Université des Sciences et Technologies de Lille , UMR 8520, Département ISEN]
Kilian, O.[Institut d’Electronique, de Microélectronique et de Nanotechnologie (IEMN), CNRS, UMR 8520, Departement ISEN ; Department of Experimental Physics, Comenius University]
Cristini-Robbe, O.[Laboratoire de Physique des Lasers, Atomes et Molécules (CNRS, UMR 8523), Bat P-5, Université des Sciences et Technologies de Lille]
Sashchiuk, A.[Schulich Faculty of Chemistry, Russell Berrie Nanotechnology Institute, Technion, Haifa]
Addad, A.[Laboratoire de Structure et Propriétés de l’Etat Solide, Université des Sciences et Technologies de Lille]
Turrell, S.[Laboratoire de Spectrochimie Infrarouge et Raman, LASIR, Université des Sciences et Technologies de Lille]
Lifshitz, E.[Schulich Faculty of Chemistry, Russell Berrie Nanotechnology Institute, Technion, Haifa]
Grandidier, B.[Institut d’Electronique, de Microélectronique et de Nanotechnologie (IEMN), CNRS, UMR 8520, Département ISEN]
Wirtz, Ludger[Institut d’Electronique, de Microélectronique et de Nanotechnologie (IEMN), CNRS, UMR 8520, Département ISEN ; University of Luxembourg > Faculty of Science, Technology and Communication (FSTC) > Physics and Materials Science Research Unit >]
[en] 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 layers. The LO mode perpendicular to the slab shifts indeed upwards with decreasing layer thickness, thus validating the interpretation of the anomalous radius dependence of the Raman spectra in terms of quantum confinement.
[Institut d’Electronique, de Microélectronique et de Nanotechnologie (IEMN), CNRS, UMR 8520, Département ISEN ; University of Luxembourg > Faculty of Science, Technology and Communication (FSTC) > Physics and Materials Science Research Unit >]
