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Resonant Raman (resonant + raman)

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Physics and Astronomy100%

Selected Abstracts

Resonant Raman scattering in spherical quantum dots: II,VI versus III,V semiconductor nanocrystals

PHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 6 2010
Mikhail I. Vasilevskiy
Abstract Resonant Raman scattering (RRS) in nearly-spherical nanocrystal (NC) quantum dots (QDs) is discussed with respect to the underlying (Fröhlich-type and optical deformation potential, ODP) mechanisms of the exciton,phonon interaction. Their relative contribution for different QD materials, both II,VI and III,V is compared. It is shown that the (usually overlooked) ODP interaction is entirely responsible for an additional peak in the RRS spectra, situated near the transverse-optical (TO) phonon frequency, which has been observed for InP, InAs and, recently, CdTe QDs. RRS spectra calculated using continuum models for confined phonons and excitons and taking into account both interaction mechanisms are in excellent agreement with these experimental data. [source]

Phonons in InAs quantum dot structures

PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 9 2009
Alexander Milekhin
Abstract We present a Raman study of the phonon spectra of periodical structures with (In,Ga)As QDs in (Al,Ga)As matrix as well as AlAs QDs embedded in InAs grown by molecular beam epitaxy. Raman scattering by optical, interface and acoustic phonons was observed in the QD structures. TO and LO phonons in the QDs are strongly affected by both strain and confinement. The Raman study reveals a two-mode behavior of optical phonons in the whole composition range for both InGaAs QDs and the AlGaAs matrix. Raman scattering by InAs- and GaAs-like LO phonons in InGaAs QDs shows a size-selective resonant behaviour. Interface phonons were investigated in InGaAs QDs and the AlGaAs matrix. Their frequency positions were analyzed as a function of the alloy content within the dielectric continuum model. The positions of IF phonons in the QD structures observed in the experiment agree well with calculated ones assuming that the QDs have the shape of oblate ellipsoids. Multiple phonon Raman scattering involving both pure overtones of the first-order InAs, GaAs and AlAs optical and interface phonons and combination of phonons from the materials is observed in the vicinity with E0 resonance in QDs. Possible mechanisms of these processes are discussed. Low frequency resonant Raman scattering by acoustic phonons was observed in the QD structures. The periodic oscillations seen in the Raman spectra are well described by the elastic continuum model. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Is polaron effect important for resonant Raman scattering in self-assembled quantum dots?

PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 2 2005
M. I. Vasilevskiy
Abstract While the diagonal (or intra-level) interaction of a confined exciton with optical phonons in self-assembled quantum dots (SAQD's) is rather weak, the non-diagonal one can lead to a considerable change of the exciton spectrum and the formation of a polaron. An impact of this effect on resonant inelastic light scattering is studied theoretically. The polaron spectrum is obtained by numerical diagonalisation of the exciton,phonon interaction Hamiltonian in a truncated Hilbert space of the non-interacting excitons and phonons. Based on this spectrum, the probability of the multi-phonon Raman scattering is calculated, which is compared to that obtained within the standard perturbation theory approach (where phonon emission and absorption are irreversible). It is shown that there are two major effects of the polaron formation: (i) the intensity of the two-phonon (2 LO) peak, relative to that of the fundamental 1 LO one is strongly increased and (ii) the resonant behaviour of the 1 LO peak differs considerably from the perturbation theory predictions. With the correct theoretical interpretation, resonant Raman scattering in SAQD's opens the possibility of accessing the (renormalised) exciton spectrum and exciton,phonon coupling constants. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]