Regensburg 2004 – wissenschaftliches Programm

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HL: Halbleiterphysik

HL 36: Quantenpunkte und -dr
ähte: Optische Eigenschaften I

HL 36.9: Vortrag

Donnerstag, 11. März 2004, 12:15–12:30, H17

Effects of oxidation on silicon nanocrystallites — •Luis Ramos, Jürgen Furthmüller, and Friedhelm Bechstedt — FSU Jena - IFTO Max-Wien-Platz, 1 D-07743 Jena Germany

The luminescence observed in porous silicon (p-Si) is known to be related to quantum confinement of carriers in the nanostructures formed at the surface of this material. Experimental observation confirms also that optical properties depend on the level of oxidation in p-Si. Spherical-like silicon nanocrystallites (NCs) have attracted special attention and several investigations have focused in the influence of surface passivation of Si NCs with H, with group OH, and with few Si=O bond terminations. However, fully oxidized shells and defects in Si NCs have not been considered so far.We apply the VASP code with PAW pseudopotentials and DFT-LDA to study the influence of oxidation on the structural and electronic properties of Si NCs. The absorption spectra of NCs obtained by means of effective medium theory are compared to experimental data. To discuss HOMO-LUMO gaps and excitonic effects we consider in addition pair excitation energies and gaps calculated in a GW approximation.