Dresden 2003 – wissenschaftliches Programm
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HL: Halbleiterphysik
HL 49: Poster II
HL 49.49: Poster
Donnerstag, 27. März 2003, 16:30–19:00, HSZ/P2
Optical properties of Si-nanoparticles in the mid IR — •Vasyl Kravets1, Cedrik Meier1, Denan Konjhodzic1, Axel Lorke1, and Hartmut Wiggers2 — 1Laboratorium für Festkörperphysik, Gerhard-Mercator Universität Duisburg, D-47048 Duisburg — 2Institut für Verbrennung und Gasdynamik, Gerhard-Mercator Universität Duisburg, D-47048 Duisburg
Rayleigh scattering of Si nanoparticles (d=50 − 300 nm) was investigated in the wavelength range of λ =2−20 µ m (mid IR). The particles used in this study were prepared by pyrolysis of silane either in a hot wall gas phase reactor or in a microwave flow reactor. The transmission spectra of the Si particles were obtained using FTIR spectroscopy measurements. The dominant features in these spectra are the optical modes arising from asymmetric Si-O stretching vibrations in the region if ν=1000 − 1300 cm−1 and a strong damping of the transmission intensity with increasing wavenumber of the incident light. We find that the dependence of the scattering cross section as a function of λ is different from the λ−4-dependence expected for Rayleigh scattering of spherical particles. For a wide distribution of particle sizes, the experimental data show a power-law-dependence of λ−2.24. As a first step to an improved model we consider Rayleigh scattering of ellipsoidal particles. The results of our simulations for Si nanoparticles coated by a layer of SiOx are in good agreement with the experimental data. This demonstrates that it is possible to estimate size, chemical properties and shape of Si nanoparticles from the transmission data.