Anisotropy of electron-phonon interaction in nanoscale CdSe platelets as seen via off-resonant and resonant Raman spectroscopy

Cherevkov, Sergei A.; Fedorov, Anatoly V.; Artemyev, Mikhail; Prudnikau, Anatol; Баранов, А. В.

doi:10.1103/physrevb.88.041303

Cited by 47 publications

(44 citation statements)

References 35 publications

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“…It corresponds well to the "low-energy shoulder (LES)" described in the experimental work 52 and which was observed in NCs with different sizes, shapes, surface environments and materials using Raman and photoluminescence measurements 33,52,[54][55][56][57][58][59][60][61] . This LES is often described as a "surface optical" phonon mode 33,52,[54][55][56][57][58][59][60][61] which is in rather good agreement with our identification. The fact, that is some surface character leads to the expectation that it will have some dependence on the type of surface passivation, in good agreement with some experiments 62 .…”

Section: Comparisonsupporting

confidence: 83%

Heavy strain conditions in colloidal core-shell quantum dots and their consequences on the vibrational properties fromab initiocalculations

Han

Bester

2015

Phys. Rev. B

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We preform large-scale ab initio density functional theory calculations to study the lattice strain and the vibrational properties of colloidal semiconductor core-shell nanoclusters with up to one thousand atoms (radii up to 15.6Å). For all the group IV, III-V and II-VI semiconductors studied, we find that the atom positions of the shell atoms, seem unaffected by the core material. In particular, for group IV core-shell clusters the shell material remains unstrained, while the core adapts to the large lattice mismatch (compressive or tensile strain). For InAs-InP and CdSe-CdS, both the cores and the shells are compressively strained corresponding to pressures up to 20 GPa. We show that this compression, which contributes a large blue-shift of the vibrational frequencies, is counterbalanced, to some degree, by the undercoordination effect of the near-surface shell, which contributes a red-shift to the vibrational modes. These findings lead to a different interpretation of the frequency shifts of recent Raman experiments, while they confirm the speculated interface nature of the low-frequency shoulder of the high frequency Raman peak.

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Section: Comparisonsupporting

confidence: 83%

Heavy strain conditions in colloidal core-shell quantum dots and their consequences on the vibrational properties fromab initiocalculations

Han

Bester

2015

Phys. Rev. B

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“…15 Comparison of the resonant and nonresonant Raman spectra of three thicknesses of CdSe NPLs, quenched with 4 benzeneselenol and deposited as films, showed LO phonon shifts implying stronger coupling of the out-of-plane phonons to the resonant excitonic transitions. 16 The LO overtone to fundamental intensity ratio decreased with decreasing NPL thickness, suggesting weaker EPC in the thinner NPLs. Both Raman and infrared spectra of CdSe NPLs and their core/shell and core/crown structures with CdS have been reported.…”

Section: Introductionmentioning

confidence: 97%

Weak Exciton–Phonon Coupling in CdSe Nanoplatelets from Quantitative Resonance Raman Intensity Analysis

Maddux

Kelley

2018

J. Phys. Chem. C

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Resonance Raman spectra, cross-sections, and depolarization ratios have been measured for 4.5 monolayer thick CdSe nanoplatelets dispersed in chloroform. Five excitation wavelengths between 514.5 and 476.5 nm were employed. The resonance Raman spectra are dominated by the longitudinal optical (LO) phonon near 201 cm-1 and its overtone, as in CdSe quantum dots. The absolute scattering intensity is much higher for excitation on resonance with the sharp, lowest-energy heavy-hole to conduction band transition than with higher energy transitions, decreasing by about a factor of 30 between 514.5 nm and 496.5 nm excitation. The LO phonon overtone is weak directly on resonance with the heavy-hole transition but much stronger at higher excitation energies, a result that is reproduced by simulations of the spectra using standard resonance Raman intensity theory. The absolute Raman cross-sections imply a Huang-Rhys parameter for the LO phonon of about 0.08 on resonance with the lowest heavyhole transition. This is a factor of 2-3 lower than found previously for CdSe quantum dots. The depolarization ratios on resonance with the lowest heavy-hole excitonic transition are slightly higher than expected for a degenerate, plane-polarized transition even when the local field factors are taken into account.

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“…The literature data on Raman and IR spectra of CdSe nanoplatelets are not too numerous. [17][18][19][20][21] The main strong peak in the Raman spectra is explained by the light scattering by LO phonons whose frequency varies with a change in the nanoplatelet thickness as a result of the spatial confinement of the phonons. The weak features observed on the low-energy side of this peak are explained by surface optical (SO) phonons.…”

Section: Introductionmentioning

confidence: 99%

“…The weak features observed on the low-energy side of this peak are explained by surface optical (SO) phonons. 17,18,21 In Ref. 17 and 18, the thickness dependence of the frequencies of LO and SO modes was studied.…”

Section: Introductionmentioning

confidence: 99%

Lattice dynamics of quasi-two-dimensional CdSe nanoplatelets and their Raman and infrared spectra

Лебедев

2017

Phys. Rev. B

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Phonon spectra of CdSe nanoplatelets (2-6 ML) with the zinc-blende structure were calculated from first principles within the density-functional theory. It turned out that the Lamb modes in nanoplatelets are in fact optical rather than acoustic vibrations. Phonon spectra of the nanoplatelets show the appearance of a large number of low-frequency modes inherited from TA phonons in bulk CdSe. Calculations of the Raman spectra indicate a need to revise the interpretation of available experimental data. The largest contribution to the Raman spectra is provided by the quasi-Lamb modes with the A1 symmetry. The B2 modes whose frequencies depend on the environment of nanoplatelets and whose properties are closest to the properties of LO phonons explain the results obtained in the "nanoparticle-on-mirror" geometry. The features in Raman spectra previously attributed to surface optical (SO) modes should be interpreted as a manifestation of lower-order quasi-Lamb A1 modes. Calculations of the infrared spectra find, in addition to the TO phonon line, the appearance of intense lines from surface modes originating from terminating F(Cl) atoms on the surface of nanoplatelets and true SO-modes.

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Anisotropy of electron-phonon interaction in nanoscale CdSe platelets as seen via off-resonant and resonant Raman spectroscopy

Cited by 47 publications

References 35 publications

Heavy strain conditions in colloidal core-shell quantum dots and their consequences on the vibrational properties fromab initiocalculations

Heavy strain conditions in colloidal core-shell quantum dots and their consequences on the vibrational properties fromab initiocalculations

Weak Exciton–Phonon Coupling in CdSe Nanoplatelets from Quantitative Resonance Raman Intensity Analysis

Lattice dynamics of quasi-two-dimensional CdSe nanoplatelets and their Raman and infrared spectra

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