Regensburg 2010 – wissenschaftliches Programm

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DS: Fachverband Dünne Schichten

DS 43: Biomolecular and Functional Organic Layers II (Focused Session)

DS 43.8: Topical Talk

Freitag, 26. März 2010, 13:30–14:00, H2

In-silico optimization of function and emissive properties of Silicon nanoparticles — •Thomas Niehaus — Bremen Center for Computational Materials Science, Bremen, Germany

Excited-state properties of silicon quantum dots (SiQDs) up to diameters of 2 nm are studied using an approximate time-dependent density-functional theory method (TD-DFTB) [1] and compared with available experimental data. Several functionalizations ranging from simple hydrogen passivation up to capping with amine [2], allyamine [3] and propionic acid [4] groups are discussed. Signatures in vibrational and optical absorption spectra are revealed, which show the detailed effect of surface modification of the SiQDs. It is verified that the modification could be expected to not only reduce the surface oxidation rate but also maintain an efficient electronic transition feature that facilitates blue emission. The obtained absorption spectra show a significant size dependence. In the case of allylamine capping, the increase in the number of attached molecules only results in a slight red shift of emission spectra. The latter are calculated by means of full geometry optimization in the excited state and reveal huge Stoke shifts in contrast to simple quantum confinement models [5].

[1] T.A. Niehaus et al., Phys. Rev. B, 63, 085108, 2001. [2] Q.S. Li et al., Appl. Phys. Lett., 92, 053107, 2008. [3] X. Wang et al., J. Phys. Chem. C, 111, 2394, 2007. [4] Q.S. Li et al., J. Chem. Theo. Comp., 3, 1518, 2007. [5] X. Wang et al., Appl. Phys. Lett., 90, 123116, 2007.