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Semiconductor Physics, Quantum Electronics & Optoelectronics. 2013. V. 16, N 1. P. 086-090.
Laser heating effect on Raman spectra of Si nanocrystals
embedded into SiOx matrix
V. Lashkaryov Institute of Semiconductor Physics, NAS of Ukraine, Optical Submicron Spectroscopy Laboratory,
45, prospect Nauky, 03028 Kyiv, Ukraine
E-mail: Nikolenko_mail@ukr.net, phone/fax: +38 (044) 525-64-73
Abstract. . 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 K-μm2/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 temperature-induced vibration anharmonicity with the decay of optical phonons through three- and four-phonon processes and corresponding anharmonic constants have been determined. Keywords: silicon nanocrystals, Raman spectroscopy, phonon confinement, laser heating.
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