Structural and opto-electronic properties of pure, doped and ligand terminated semiconductor nanoclusters

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Semiconductor nanoclusters are promising building blocks for optical and electronic applications in nanotechnology. Therefore, the understanding of their physical and chemical properties in dependence on cluster size and chemical composition is crucial. In the present project we aim for a systematic investigation of semiconductor nanoclusters employing a combined approach. For this purpose not only pure semiconductor nanoclusters based on Si and CdSe but also doped and ligand terminated species will be prepared in the gas phase and characterized by mass spectrometry. The geometrical and electronic structure of the clusters are determined by means of electric deflection studies and laser dissociation spectroscopy. The experimental examinations are supported by in-depth quantum chemical investigations, which are carried out in close cooperation with the quantum chemistry group of Prof. V. Krewald (Technische Universität Darmstadt). The scope of these calculations is to study the optical properties of various structural isomers of a given cluster size and to analyze the opto-electronic properties more precisely in comparison with the experimental data. In particular, the influence of cluster size and doping with defect electrons on the first optical transition, i.e. the colour, is of special interest. Further, the effects of ligand termination (H2 for Si and H2S for CdSe clusters) on the opto-electronic properties shall be clarified. The main aim is to work out how the electronic structure and the optical behavior change from molecule-like clusters to solid-state-like nanocrystallites. The suggested investigations allow therefore to pursue the transition from atomic to mesoscopic length scales and also to explore possible applications of semiconductor nanoclusters consequently.