Diffusion-limited growth in a glass matrix is a well elaborated technique to obtain ternary II-VI semiconductor nanocrystals where the confined exciton energy gap can be tuned by both compositional and size variation. Contrary to the CdS_1-xSe_x system, the phonon spectra of which have been studied quite extensively, glass-embedded ternary CdSe_1-xTe_x nanocrystals are much less investigated. CdSe_1-xTe_x is known to be a solid solution system with a two-mode phonon spectrum transformation type, hence one can try to use phonon spectroscopy as an efficient and  non-destructive tool to determine the nanocrystal composition.

Here we report on the studies of phonon spectra of CdSe_1-xTe_x nanocrystals obtained in a borosilicate glass by diffusion-limited growth by heat treatment during 2–12 h at the temperatures ranging from 625 to 700^oC, resulting in the variation of the nanocrystal composition and size. Resonant Raman scattering studies were performed using a Dilor XY 800 triple monochromator with a CCD camera with excitation by a Kr⁺ ion laser (647.1 and 676.4 nm). The measurements were carried out at room temperature.

First- and second- order Raman spectra of CdSe_1-xTe_x nanocrystals were measured. The data obtained are compared with those for for the relevant bulk crystals obtained by Raman and infrared spectroscopy as well as with scarce data of other authors for CdSe_1-xTe_x nanocrystals. The accuracy of determination of the nanocrystal composition from the phonon spectra is estimated.

A Raman feature near 215 cm-1, observed in the spectra of CdSe_1-xTe_x nanocrystals, obtained at the heat treatment durations and temperatures below the optimal values for the nanocrystal formation, is attributed to vibrations of anion clusters being formed as an alternative to the diffusion-limited formation of II-VI nanocrystals.

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