4 research outputs found
Electron and Phonon Confinement and New Surface Phonon Modes in CdSe-CdS Core-Shell Nanocrystals
Optical and vibrational properties of bare and CdS shelled CdSe
nanocrystalline particles are investigated. To confirm the formation of such
nanocrystals in our samples we estimate their average particle sizes and size
distributions using TEM measurements. From the line profile analysis of the
images the core-shell structure in the particles has been confirmed. The blue
shift in optical absorption spectra, analyzed using theoretical estimates based
on the effective bond order model, establishes the electron confinement in the
nanoparticles. Unique characteristics of the nanocrystals (which are absent in
the corresponding bulk material), such as confinement of optical phonons and
the appearance of surface phonons, are then discussed. Making use of the
dielectric response function model we are able to match the experimental and
theoretical values of the frequencies of the surface phonons. We believe that
our studies using optical probes provide further evidence on the existence of
core-shell structures in CdSe-CdS type materials.Comment: 19 pages 8 figure