Spectroscopy and Dynamics of Semiconductor Clusters

本项目利用几种基于负离子光分离的实验技术，重点研究了尺寸选定的IV族和III-V族半导体团簇的光谱和动力学，以表征这些物种的性质如何随着尺寸和化学计量比的变化而变化。相应的块状化合物在半导体和电子工业中起着关键作用，因此这些研究与纳米器件技术高度相关，因为它们探索了块状材料的性质是如何从它们的原子和分子组成演变而来的。该项目将重点放在二元III-V氮化物化合物、硅簇和磷化铟簇上。我们感兴趣的性质包括小团簇中的振动频率和电子态分裂，价带和导带随团簇尺寸的增加而演变，团簇激发态中的电子弛豫动力学，以及光解引起的碎裂模式。在所有的实验中，都产生了半导体团簇阴离子的质量选择束并被光分离。主要的实验方法是固定频率阴离子光电子能谱，它提供了一种确定尺寸选择的中性团簇的电子结构和振动结构的一般手段。这项技术将得到可调谐激光光分离、时间分辨光电子能谱和快束光碎片平移光谱学实验的补充。了解物质的物理和化学性质如何随着尺寸的变化对许多潜在的应用至关重要，这些应用旨在满足重大的社会需求。重点放在选择的元素簇上，对于这些元素簇，相应的大块化合物在制造晶体管和光电二极管等快速器件方面发挥着重要作用。拟议的研究之所以重要，是因为它们为未来的科学家和工程师提供了国家利益关键领域的培训。

This project focuses on the spectroscopy and dynamics of size-selected group IV and III-V semiconductor clusters using several experimental techniques based on negative ion photodetachment to characterize how the properties of these species vary with size and stoichiometry. The corresponding bulk compounds play a key role in the semiconductor and electronics industries so these studies are highly relevant to nano-device technologies in that they probe how the properties of the bulk materials evolve from their atomic and molecular constituents. The project will focus on binary III-V nitride compounds, silicon clusters, and indium phosphide clusters. Properties of interest include vibrational frequencies and electronic state splittings in small clusters, the evolution of valence and conduction bands as the cluster size increases, electronic relaxation dynamics in excited states of the clusters, and the fragmentation patterns resulting from photodissociation. In all the experiments, mass-selected beams of semiconductor cluster anions are generated and photodetached. The primary experimental method is fixed-frequency anion photoelectron spectroscopy, which provides a general means to determine the electronic and vibrational structure of a size-selected neutral cluster. This technique will be complemented by tunable laser photodetachment, time-resolved photoelectron spectroscopy, and fast beam photofragment translational spectroscopy experiments.%%%Understanding how physical and chemical properties of matter evolve with size is crucial to many potential applications designed to meet significant societal needs. Emphasis is placed on select elemental clusters, for which the corresponding bulk compounds play a major role in the fabrication of fast devices such as transistors and photodiodes. The proposed studies are important because they provide training for future scientists and engineers in key areas of national interests.