Анотація:
Influence of combined size confinement effect and effect of local laser heating
on the first-order Raman spectrum of silicon nanocrystals embedded into SiOx matrix has
been studied. Increase of the local temperature of Si nanocrystals caused by laser
illumination with the power density up to 10 mW/μm² was estimated from the ratio of
the Stokes/anti-Stokes peak intensities. Almost linear dependence of nanocrystals local
temperature on the power density of exciting radiation with a rate of 63.6 Km² /mW has
been found. The phonon line shape at power densities, when no laser heating effect is
registered, was shown to be described well within the correlation length model of phonon
confinement of Si nanocrystals with the size L = 9.2 nm. Observed phonon softening and
broadening with increase of the exciting power density is considered as temperatureinduced vibration anharmonicity with the decay of optical phonons through three and four-phonon processes and corresponding anharmonic constants have been determined.