The phonon dispersion of wurtzite CdSe

Widulle, F.; Kramp, S.; Pyka, N.; Göbel, A.; Ruf, T.; Debernardi, A.; Lauck, R.; Cardona, M.

doi:10.1016/s0921-4526(98)01245-9

Cited by 50 publications

(55 citation statements)

References 6 publications

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“…The paths in reciprocal space were chose as Γ → A for the WZ phase and Γ → L for the ZB phase. For WZ-CdX, the calculated phonon dispersion curves are in excellent agreement with the inelastic neutron scattering data 79,83 and DFT computations. 79,80 For ZB-CdX, there are no experimental data available for comparison.…”

Section: Physical Properties Of Cds Cdse Pbs and Pbse Binary supporting

confidence: 73%

A transferable force field for CdS-CdSe-PbS-PbSe solid systems

Fan

Koster

Wang

et al. 2014

The Journal of Chemical Physics

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A transferable force field for the PbSe-CdSe solid system using the partially charged rigid ion model has been successfully developed and was used to study the cation exchange in PbSe-CdSe heteronanocrystals [A. O. Yalcin et al., “Atomic resolution monitoring of cation exchange in CdSe-PbSe heteronanocrystals during epitaxial solid-solid-vapor growth,” Nano Lett. 14, 3661–3667 (2014)]. In this work, we extend this force field by including another two important binary semiconductors, PbS and CdS, and provide detailed information on the validation of this force field. The parameterization combines Bader charge analysis, empirical fitting, and ab initio energy surface fitting. When compared with experimental data and density functional theory calculations, it is shown that a wide range of physical properties of bulk PbS, PbSe, CdS, CdSe, and their mixed phases can be accurately reproduced using this force field. The choice of functional forms and parameterization strategy is demonstrated to be rational and effective. This transferable force field can be used in various studies on II-VI and IV-VI semiconductor materials consisting of CdS, CdSe, PbS, and PbSe. Here, we demonstrate the applicability of the force field model by molecular dynamics simulations whereby transformations are initiated by cation exchange.

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Section: Physical Properties Of Cds Cdse Pbs and Pbse Binary supporting

confidence: 73%

A transferable force field for CdS-CdSe-PbS-PbSe solid systems

Fan

Koster

Wang

et al. 2014

The Journal of Chemical Physics

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“…The strong neutron absorbing nature of Cd forbids such experiments. The phonon dispersion of bulk CdSe was measured by inelastic neutron scattering on the very weakly neutron absorbing isotope 116 Cd and natural selenium [49]. But creating precursors with sufficient amounts of this CdSe isotope is extremely complex.…”

Section: Chapter 3 Methodsmentioning

confidence: 99%

“…treat confined phonons or heat transfer. For the direction Γ − A ab initio calculations, a shell-model and inelastic neutron scattering data are available [49]. The inelastic neutron scattering measurements were performed with a crystal containing the weak neutron absorbing isotope 116 Cd.…”

Section: Cdse Phonon Dispersionmentioning

confidence: 99%

Optical phonons in colloidal CdSe nanorods

Lange

Mohr

Artemyev

et al. 2010

Physica Status Solidi (b)

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Colloidal CdSe nanorods are nanoparticles synthesized in solution. The synthesis allows the growth of CdSe nanorods with well defined diameters and aspect ratios. They have many potential applications in the field of optoelectronics and biotechnology. The nanorods can be epitaxially covered with a graded CdS/ZnS shell of a few monolayers in thickness. The shell leads to an increased quantum efficiency and improved photostability of the nanorods. However, the lattice mismatch between the nanorod core material and the shell material introduces strain into the core lattice. In this work Raman spectroscopy, accompanied by ab-initio calculations, is used to determine the amount of this strain, the exciton-phonon coupling strength in the nanorods and to investigate confinement effects. The longitudinal optical phonons in a nanorod are confined to the nanorod volume. The confinement of a phonon wavefunction leads to a neutralization of the q = 0 rule and the phonon frequency is found to depend on the nanorod diameter. The coupling strength between longitudinal optical phonons and excitons is investigated. It also depends on the nanorod diameter. The total coupling strength is much lower than in bulk material due to a decrease of the influence of the Coulomb interaction in nanoparticles. However, the coupling strength is found to rise for decreasing diameters. This is due to the increasing contributions of higher frequency phonons for smaller nanoparticle sizes. A radial breathing mode with a diameter dependent frequency is deduced from ab-initio calculations and its existence in nanorods is verified experimentally. The diameter-dependence of the modes' frequency can be used to estimate the nanorod diameter from a Raman measurement. In core-shell structures, the coverage of a CdSe nanorod with a ZnS shell leads to a compressive strain of the CdSe core due to the smaller lattice parameter of ZnS compared to CdSe. Ab-initio calculations show that all bonds of the CdSe core are shortened. The bonds in the lateral direction are much more strongly compressed than the bonds parallel to the c-axis. The amount of strain is estimated from the Raman spectra. The compressive nature of the shell decreases for thicker nanorods. The exciton wave function changes with the modified boundary from air to ZnS. This is reflected in a altered exciton-phonon coupling strength and can be monitored in the Raman spectra. ZusammenfassungCdSe Nanorods sind Nanopartikel, die in einer kolloidalen Lösung synthetisiert werden. Für diese existieren viele mögliche Anwendungen im Bereich der Optoelektronik und der Biotechnologie. Der Durchmesser und die Länge der Nanorods lässt sich durch die Syntheseparameter festlegen. Die Nanorods können in eine epitaktische Hülle aus einem Halbleitermaterial mit einer größeren Bandlücke, ZnS, eingebettet werden. Diese Hülle verbessert die optischen Eigenschaften und ermöglicht eine weitere Funktionalisierung der Oberfläche. Der Unterschied der Gitterparameter zwischen ZnS und CdSe führt jedoch zu Verspannung...

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“…The experimental data shown in the figure correspond to Ref. [6] and refer only to the G±A direction. We can observe a good agreement obtained with the model in comparison with the experiment.…”

Section: Resultsmentioning

confidence: 97%

“…Recently, and thanks to the availability of a large amount of isotopically pure semiconductors, crystals with the low neutron absorber 114 Cd have been grown and the experimental phonon dispersion of CdSe [6] as well as that of CdS [7] have been measured. The CdSe data are compared with ab initio calculations and a 24 parameter shell model, whose force constants are re-scaled from the fit of the CdS dispersion.…”

mentioning

confidence: 99%

Phonon Dispersion of Wurtzite CdSe: The Bond Charge Model

Camacho

Cantarero

2000

phys. stat. sol. (b)

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The phonon dispersion of wurtzite CdSe is presented along the main directions of the Brillouin zone. The study has been performed by using a bond charge model for wurtzite‐type semiconductors with only six adjustable parameters. The results are compared against neutron scattering data and ab initio calculations. The phonon eigenvectors corresponding to the vibrational modes at the Γ‐point are in very good agreement with the ab initio calculations.

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The phonon dispersion of wurtzite CdSe

Cited by 50 publications

References 6 publications

A transferable force field for CdS-CdSe-PbS-PbSe solid systems

A transferable force field for CdS-CdSe-PbS-PbSe solid systems

Optical phonons in colloidal CdSe nanorods

Phonon Dispersion of Wurtzite CdSe: The Bond Charge Model

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