Dresden 2006 – wissenschaftliches Programm
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HL: Halbleiterphysik
HL 19: Quantum dots and wires: Optical properties II
HL 19.9: Vortrag
Dienstag, 28. März 2006, 19:15–19:30, HSZ 01
Optical Spectroscopy on Silicon Nanoparticles — •Stephan Lüttjohann1, Cedrik Meier1, Andreas Gondorf1, Axel Lorke1, and Hartmut Wiggers2 — 1Laboratorium für Festkörperphysik, Universität Duisburg–Essen, 47048 Duisburg — 2Institut für Verbrennung und Gasdynamik, Universität Duisburg–Essen, 47048 Duisburg
The optical properties of silicon nanoparticles have been studied by photoluminescence and Raman spectroscopy. The particles are fabricated in a low pressure microwave reactor by decomposition of silane.
We have investigated particles in a size range of between d=4.2nm and 60nm. For particles with diameters smaller than 30nm, quantum effects become relevant and are observed in Raman spectra as well as in photoluminescence spectra. The Raman spectra show the phonon confinement effect which redshifts the energy of the observed phonons.
The PL emission wavelength (between 600nm and 1000nm) shifts towards lower wavelengths with decreasing particle sizes. Investigations of the PL intensity as a function of the temperature reveal an interesting behaviour. The PL intensity has a maximum at about T=80K and decreases for higher as well as lower temperatures.
To get a better understanding about the origin of these effects, micro-photoluminescence is employed. First results showing sharp emission lines (FWHM ≈ 1meV) originating from excitonic and biexcitonic recombination are presented. As a result of the strong Coulomb interaction in the particles the spectra show a remarkable high exciton to biexciton energy splitting of 32meV.