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有前途的构建块。因此，了解它们的物理和化学性质依赖于集群的大小和化学成分是至关重要的。在本项目中，我们的目标是系统的调查半导体纳米团簇采用组合的方法。为了这个目的，不仅纯的半导体纳米团簇的基础上Si和CdSe，但也掺杂和配体终止的物种将在气相中制备，并通过质谱法进行表征。团簇的几何结构和电子结构的确定通过电偏转研究和激光解离光谱。实验检查得到了深入的量子化学研究的支持，这些研究是与达姆施塔特工业大学的V.Krewald教授的量子化学小组密切合作进行的。这些计算的范围是研究一个给定的集群大小的各种结构异构体的光学性质和分析的光电性能更精确地与实验数据相比。特别是，集群的大小和掺杂的缺陷电子上的第一个光学跃迁，即颜色的影响，是特别感兴趣的。此外，配体终止（H2的Si和H2S的CdSe簇）的光电性能的影响应澄清。主要目的是研究从分子团簇到固态纳米晶体的电子结构和光学行为的变化。因此，建议的调查允许追求从原子到介观的长度尺度的过渡，并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.