Yu. M. Azhniuk

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.

Optical studies of CdSe/HgSe and CdSe/Ag2Se core/shell nanoparticles embedded in gelatin

CdSe/HgSe and CdSe/Ag2Se core–shell nanoparticles are obtained by colloidal synthesis from aqueous solutions in the presence of gelatin. Optical absorption, luminescence, and Raman spectra of the nanoparticles obtained are measured. The variation of the optical spectra of CdSe/HgSe and CdSe/Ag2Se core–shell nanoparticles with the shell thickness is discussed. Sharp non-monotonous variation of the photoluminescence spectra at low shell coverage is observed.

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.

Disorder Effects and Resonant Features in Raman Spectra of Electron-irradiated GaP and CdS Crystals

Electron-irradiated (by 7-14 MeV electrons) GaP and CdS crystals and CdS-based solid solutions were studied by Raman scattering. Disorder-activated acoustic phonon bands are revealed in the GaP spectrum with increase of the irradiation dose. Broadening of the TO-phonon band in irradiated GaP samples is observed. The behaviour of the LO- and 2LO-phonon resonant Raman scattering versus irradiation dose is discussed, the resonant conditions being tuned by variation of exciting light energy and crystal composition.