Investigation of phonon quantization and electron-phonon interaction in semiconductor nanoparticles by the Raman scattering and photoluminescence |
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The project aimed at the development of nanophononics, a
new field of nanoscale science, which deals with the properties of
phonons in nanostructures and control of phonon dispersion in
nanostructures, hence, with phonon engineering.The first step to create
the electronic devices with sizes, smaller than mean free length of
acoustic phonons, is the determination of the physical picture of
microscopic processes, which is the basis of interaction between electron
and acoustic phonons in nanostructures with different dimensions. At the
reporting period in the frame of our project it were carried out the
theoretical and experimental studies of the characteristic features of
low-frequency Raman spectra of the Ge quantum dots in dielectric matrix
GeO2, and of quantum films with the thicknesses equal to the quantum dot
size. It was shown that embedding of nanocrystalls to dielectric leads to
arising the new surface vibrations defined by the restoring force due to
the nanocrystalls rotation. These vibrations determine the low-frequency
Raman spectra. It was established that the electron-acoustic phonon
interaction in QD´s occurs not through the deformation potential, but due
to an electron perturbation from the nanostructure interface vibrations.
When analyzed the Raman spectra on the acoustic vibrations of thin films,
it was shown that the existence of the resonance phonon mode in the film
grown on the substrate is the result of the interaction between the
continuum of the phonon states in substrate and quasi-local mode in film.
The large dispersion of QD´s sizes in dielectric matrix GeO2 that grown by
the vapor-phase deposition limits the possibilities of their using in
promising devices of nanophononics. The methods of nanocrystalls growth
that turn out to increase the QD´s homogeneity and form the nanocrystalls
placed on one plane, were proposed and realized in this project. These
techniques allow to form mechanical untied nanocrystalls that is the
important thing for the observation of the phonon localization.
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