Dresden 2006 – wissenschaftliches Programm

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CPP: Chemische Physik und Polymerphysik

CPP 2: Colloids and Nanoparticles

CPP 2.3: Vortrag

Montag, 27. März 2006, 10:30–10:45, ZEU 160

Detailed structural analysis of wet-chemically synthesized II-VI semiconductor nanoparticles — •Franziska Niederdraenk¹, Pawel Luczak¹, Andreas Stahl¹, Christian Kumpf¹, Reinhard Neder², and Eberhard Umbach¹ — ¹Experimentelle Physik II, Univ. Würzburg — ²Inst. für Mineralogie und Kristallstrukturlehre, Univ. Würzburg

The determination of the detailed geometric structure of nanoparticles with diameters below 5 nm is of particular interest since these particles represent the transition regime between molecular and solid state physics. In principle, diffraction methods provide this information, but crystallographic analysis techniques, like the Rietveld refinement or a size determination with the Scherrer equation were developed for large particles (> 10 nm) and are not reliable any more below 5 nm.

To cope with this difficulty, we model the entire nanoparticle and use the Debye formula to calculate its powder diffraction pattern. This method allows us to directly determine intrinsic parameters which cannot be treated by most of the established crystallographic techniques, e.g. size-distributions, different shapes, stacking faults, strain, etc. The Debye formula has been embedded in an evolutionary algorithm, which enables an automatic refinement of the primary atomic model. Distributions of parameters are now considered, which are essential since they are likely to occur in wet-chemically synthesized particles. We present model calculations for ZnO, CdSe and CdSe/ZnS core-shell nanoparticles in the range of 2 - 10 nm and compare them with experimental data.