Acoustic vibrations of semiconductor nanocrystals in doped glasses

Abstract

Polarization-dependent low-frequency off-resonant Raman scattering has been studied from various commercially available filter glass samples, which contain CdS x Se 1Ϫx nanoparticles embedded in a glass matrix. In order to distinguish the confined acoustic phonons from the glass background, the spectra have been compared with those obtained from the base material, which does not contain nanoparticles. Polarized and depolarized scattering from confined acoustic phonons was distinctly resolved near the laser line and overtones of the polarized modes were observed. A theoretical treatment, which establishes a relation between the particle size, the frequencies, and the widths of various phonons, taking into account the matrix influence on the vibrational spectrum and on its damping, is presented. The material-dependent generalized form of this model enables one to use it for any given combination of particle and matrix materials. A good agreement between the experimental and the theoretical results is found. The nanoparticle sizes obtained from Raman scattering agree well with those obtained from transmission electron microscope and anomalous small angle x-ray scattering experiments. ͓S0163-1829͑99͒07231-8͔

Precipitates of selenium and tellurium in II–VI nanocrystal‐doped glass probed by Raman scattering

“…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].…”

Size dependence of nanostructures: Impact of bond order deficiency

“…The surface quadrupole mode (l ¼ 2) appears in both polarized and depolarized geometry, whereas the surface symmetrical mode (l ¼ 0) appears only in the polarized geometry. The relation between the particle size and the frequency of the polarized acoustic phonon can be established from [446]: sinðxÞ ¼ 4n 2 eff j 1 ðxÞ with complex argument,…”

Longitudinal versus transverse spheroidal vibrational modes of an elastic sphere

“…Many experiments have observed peaks in Raman spectra attributed to acoustic phonon vibrations of silver 8,9,10,11,12,13,14 silicon 15, 16 and CdS x Se 1−x . 17,18,19,20,21 These studies have regularly succeeded in observing the (SPH,2,0) mode and the (SPH,0,0) mode. A number of studies have seen (SPH,0,n) with n up to 4 14 .…”