Photodetachment Spectroscopy of Semiconductor Clusters and Nanocrystals

两种不同尺寸范围的半导体团簇 接近物质的分子和材料极限， 使用负离子光剥离 技术. 一组实验的目的是在振动和 3-20个原子大小的小团簇的电子光谱 范围;感兴趣的具体系统包括元素簇， 硅和锗以及混合III-V GaAs、InP和InSb 集群 实验结果与ab 其他人的从头计算将提供一个详细的探测如何 这些团簇的结构和化学键合随 他们的大小。 第二组实验主要集中在 在1000年的CdS和CdSe的更大的半导体“纳米晶体” 原子大小范围。 他们计划进行光电子能谱分析 对大小选择的阴离子，以确定 中性粒子的电子亲合能和电子态能量 纳米晶体 这些实验将提供一个详细的探索， 量子限域对电子结构的影响 这些物种。 此外，振动激发的程度 在光电子能谱中， 由于存在额外的电子， 负离子。 这项赠款是由材料司共同支持的 研究和化学部门。

Semiconductor clusters in two very different size ranges approaching the molecular and materials limits of matter will be studied using a combination of negative ion photodetachment techniques. One set of experiments is aimed at the vibrational and electronic spectroscopy of small clusters in the 3-20 atom size range; specific systems of interest included elemental clusters of silicon and germanium as well as mixed III-V GaAs, InP, and InSb clusters. A comparison of their experimental results with the ab initio calculations of others will provide a detailed probe of how the structure and chemical bonding of these clusters varies with their size. The second set of experiments focusses on considerably larger semiconductor 'nanocrystals' of CdS and CdSe in the 1000 atom size range. They plan to perform photoelectron spectroscopy on size-selected nanocrystal anions in order to determine the electron affinities and electronic state energies of the neutral nanocrystals. These experiments will provide a detailed probe of the effect of quantum confinement on the electronic structure of these species. In addition, the extent of vibrational excitation in the photoelectron spectrum will reveal the extent of lattice distortion caused by the presence of the additional electron in the nanocrystal anion. This grant is supported jointly by the Division of Materials Research, and the Chemistry Division.