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Quaternary Cd1–y Zny S1–x Sex nanocrystals are obtained in a borosilicate glass matrix by solid‐state precipitation at temperatures within 625 to 700 °C. Raman spectroscopy is applied to determine the nanocrystal composition and to show its dependence on the heat treatment temperature and duration. Diffusion‐induced migration of Zn ions from the matrix to the NCs results in its content increase up to ∼20% at the heat treatment; meanwhile for Se‐rich NCs an increase of Se content is also observed. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Micro-Raman spectra of CdS and CdSe nanocrystals embedded in different dielectric media (borosilicate glass, gelatin, polyacrylamide, polyvinyl alcohol) are studied. The observed Raman features are discussed with the account of confinement-related selection rules relaxation, scattering by surface phonons, and host matrix pressure. For nanocrystals grown in borosilicate glass a pronounced resonant dependence of surface phonon frequency on the excitation wavelength is observed. The effect of the excitation wavelength is much stronger than that of the nanocrystal size or the dielectric matrix type.

A series of samples with quaternary CdS1−x−ySexTey nanocrystals with cations of three types distributed over nanocrystal lattice sites were grown in a borosilicate glass matrix by the diffusion-limited growth technique. Their Raman spectra confirm the three-mode compositional behaviour of CdS1−x−ySexTey phonon spectra. The compositional dependence of the LO phonon frequencies is analysed experimentally for a series of samples containing nanocrystals with x≈y.

Phonon spectra of CdSe1–x Tex nanocrystals grown in a borosilicate glass matrix, are studied by Raman spectroscopy. The experimental data are compared to those obtained by other authors for bulk and nanoscale CdSe1–x Tex. With the account of the factors specific for glass‐embedded nanocrystals, Raman spectroscopy is shown to be a reliable and non‐destructive method to evaluate the ternary nanocrystal composition. Raman measurements performed at different excitation wavelengths enabled the compositional dispersion of the nanocrystals to be estimated. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

, Phone: þ380 312 643822, Fax: þ380 312 643650As follows from Raman studies, the formation of cadmium chalcogenide nanocrystals in borosilicate glass under thermal treatment at 625-700 8C can be accompanied by precipitation of elemental Se or Te in the form of molecular Se 2 or Te 2 clusters or larger aggregations. The clusters are in most cases formed when the thermal treatment temperature and/or duration values are beyond the range most suitable for the formation of the II-VI nanocrystals. Larger aggregations are formed at intense thermal treatment, precipitation of tellurium being achieved much easier than that of selenium.1 Introduction II-VI (mostly CdSe 1Àx S x ) semiconductor nanocrystal-doped glasses were extensively studied by Raman spectroscopy and the excellent applicability of this technique to determine the nanocrystal parameters was demonstrated. Low-wavenumber Raman scattering by acoustic phonons due to the confinement-related selection rules relaxation in CdSe 1Àx S x nanocrystals was used to estimate the average nanocrystal size [1][2][3][4][5]. Raman spectroscopy was also proven to be a very efficient tool to examine the chemical composition of ternary II-VI nanocrystals diluted in the glass matrix, based on the LO phonon frequencies taking into account the specific effects related to glass matrix pressure, phonon confinement, surface phonon scattering and compositional and size dispersion of nanocrystals within the ensemble [6][7][8][9][10][11][12][13][14][15][16][17][18].Fabrication of II-VI semiconductor nanocrystals in glass matrices is performed by a well-elaborated diffusion-limited growth technique [19][20][21]. Recently Raman scattering studies revealed that not only the nanocrystal size, but also their composition is affected by the growth conditions (thermal treatment temperature and duration) [16,18]. Moreover, it was reported that at certain thermal treatment conditions molecular clusters of selenium can be formed in CdSe and CdSe 1Àx S x nanocrystal-doped glasses [22].

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