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

半导体纳米团簇是纳米技术中光学和电子应用的重要组成部分。因此，了解它们的物理和化学性质取决于簇大小和化学组成是至关重要的。在本项目中，我们的目标是采用组合方法对半导体纳米团簇进行系统研究。为此，不仅可以制备基于Si和CdSe的纯半导体纳米团簇，还可以制备掺杂和配体终止的物质，并用质谱法对其进行表征。通过电偏转研究和激光解离光谱测定了团簇的几何和电子结构。实验检查得到了深入的量子化学研究的支持，这些研究是与V. Krewald教授的量子化学小组（Technische Universität Darmstadt）密切合作进行的。这些计算的范围是研究给定簇大小的各种结构异构体的光学性质，并与实验数据比较更精确地分析其光电性质。特别是，团簇大小和掺杂缺陷电子对第一光学跃迁（即颜色）的影响是特别值得关注的。此外，配体末端（H2为Si簇，H2S为CdSe簇）对光电性质的影响将被澄清。主要目的是研究电子结构和光学行为是如何从类分子簇转变为类固态纳米晶体的。因此，建议的研究允许追求从原子到介观长度尺度的转变，并因此探索半导体纳米团簇的可能应用。

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.