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HL: Fachverband Halbleiterphysik

HL 94: Quantum wires and nanocrystals: Optical properties

HL 94.6: Talk

Friday, March 15, 2013, 10:45–11:00, H13

Band structure and photoluminescence on silicon nanocrystals — •Prokop Hapala and Pavel Jelinek — Institute of Physics , Academy of Sciences of the Czech Republic, Cukrovarnická 10, Prague, 16253, Czech Republic

Since the first observation of photoluminescence in silicon nanocrystals (SiNCs) there is a debate whether the band structure theory is appropriate to make any statements about this kind of systems. While translational symmetry - the fundamental assumption of Bloch theorem - is violated, the only rigorous treatment would be considering SiNC as a molecule with molecular orbitals (MOs) instead of bands. On the other hand, in literature it is common practice to use band structure arguments, such as "(in-)direct band gap" to rationalize optical properties of NCs. We analyze band structure of up to 3nm SiNCs using Fourier transform of MOs obtained from DFT calculations. By this method we can rationalize effects of surface passivation (-OH, -CHO, -H, -CH3) and size (1.5-3nm) on optical properties of SiNCs.