A. V. Gomonnai

Resonant Raman studies of compositional and size dispersion of CdS1-xSex nanocrystals in a glass matrix

Resonant Raman scattering spectra of glass-embedded CdS1−x Sex nanocrystals are measured and complemented with TEM and optical absorption as well as photoluminescence data. The selectivity of the resonant Raman process not only fo rt he size, but also for the composition of nanocrystals within the ensemble, is directly observed in the dependence of phonon band frequency, linewidth and shape on the excitation wavelength.

X-ray diffraction and Raman scattering in SbSI nanocrystals

Lattice structure and rod-like shaped SbSI nanocrystals obtained by ball milling with rod thickness down to 70 nm, as estimated from X-ray diffraction (XRD) and electron microscopy, is similar to that of the bulk crystals. The dependence of the grain size on the milling duration is discussed in view of the chain-like crystalline structure of SbSI. Possible factors, responsible for the observed Raman line broadening, are discussed, scattering by surface phonons being considered the predominant one.

Interplay of factors affecting Raman scattering in cadmium chalcogenide nanocrystals in dielectric media

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.

Resonant Raman scattering studies of Cd1-xZnxS nanocrystals

Optical phonons in Cd1-xZnxS nanocrystals embedded in borosilicate glass are studied by resonant Raman scattering. A Raman-based assessment of the nanocrystal composition is performed. Compositional dispersion of the nanocrystals within the ensemble is revealed. The effect of confinement-related selection rules relaxation, scattering by surface phonons, and host matrix pressure on the Raman lineshape is analyzed.

Photoinduced Changes in the Structure of As2S3-Based SbSI Nanocrystal-Containing Composites Studied by Raman Spectroscopy

Raman studies of (As2S3)1- x (SbSI) x glasses (0.2 ≤ x ≤ 0.7) are performed. Laser-induced crystallization of SbSI crystallites in the As2S3 glass composite in the course of the measurement is observed as a result of local laser beam heating. Simultaneously a photoplastic effect in the As2S3/SbSI composite leading to a mass transfer from the laser spot is observed.

X-ray irradiation-induced ionization of CdS1−xSex nanocrystals embedded in borosilicate glass

Optical absorption spectra of x-ray irradiated CdS1−xSex nanocrystals embedded in a borosilicate glass matrix are studied. The observed transformation of the confinement-related features in the spectra is related to the x-ray-induced negative ionization of the nanocrystals with charge transfer across the nanocrystal/matrix interface. The radiation-induced changes and their relaxation upon postirradiation storage as a function of nanocrystal size and composition are discussed.

Raman and x-ray diffraction studies of nanometric Sn2P2S6 crystals

Nanometric Sn2P2S6 crystalline powders and ceramics are studied by x-ray diffraction and Raman spectroscopy. The average crystallite size is estimated from TEM and x-ray data. The observed features in the Raman spectra are discussed in view of confinement-related selection rules relaxation, surface phonon modes and possible partial substitution of sulfur by oxygen at the nanometric powder surface.

Spectral dependences of thermally stimulated luminescence and X-ray luminescence of single-crystalline and glassy Li2B4O7:Mn

Thermally stimulated luminescence (TSL) and X-ray excited luminescence (XL) spectra of single-crystalline and glassy Li2B4O7:Mn (LTB:Mn) are studied. For single-crystalline LTB:Mn, maxima at the TSL spectral dependences at 608±2 and 598±2 nm are revealed, their position being practically unchanged in a wide range of manganese dopant concentrations and irradiation doses. In the TSL and XL spectral dependences of glassy LTB:Mn, a smeared, low-intensity peak is observed, its maximum being shifted towards longer wavelengths in comparison to single-crystalline LTB:Mn. In the LTB:Mn single crystals, manganese mostly forms point defects of a Mn type, the superfluous charge being compensated by cationic vacancy. In glassy LTB:Mn, due to the decrease in packing density of the main structural blocks and because of the decreasing [BO3] triangle to [BO4] tetrahedron ratio, some Mn2+ ions are oxidized to Mn3+, resulting in the features of the spectral characteristics of TSL.

Irradiation-induced ionization of glass-embedded CdS1−xSex nanocrystals

Abstract Based on optical absorption and photoluminescence studies of CdS 1− x Se x nanocrystals embedded in borosilicate glass matrix under X-ray and electron irradiation a conclusion is made on the radiation-induced ionization of the nanocrystals. Alternative mechanisms which could explain the observed smearing and vanishing of confinement-related maxima in the absorption spectra and the absorption edge blue shift, are shown to be insignificant.

The effect of size factor on the phase transition in Sn 2 P 2 S 6 crystals: experimental data and simulation in ANNNI model

Similar features (Raman peak frequency decrease, broadening and asymmetry,whicharegenerallymorepronouncedatthecrystalsizedecrease) havebeenobservedearlier for the Raman spectra of microcrystalline Si, III-V and II-VI semiconductors[8{10]wheretheyareexplainedbytwomainfactors:(i)con nement-relatedselectionrules relaxation and contribution of q 6= 0 phonons due to the small crystallite sizeand (ii) surface phonon modes whose role in the Raman spectrum increases in micro-crystals due to much higher surface-to-volume ratio.Since in our case, contrary to some other Raman bands in Sn