若干半导体纳米簇材料几何结构和相关性质的理论研究

【作者】 王若曦；

【导师】 刘成卜；

【作者基本信息】 山东大学 ， 物理化学， 2006， 博士

【摘要】 继Kroto等于1985年在激光溅射石墨时发现了C₆₀富勒烯和日本的Iijima在1991年成功合成碳纳米管之后，半导体纳米团簇成为团簇科学领域研究的热点，尤其以碳、硅、硼为基的半导体团簇，在电子学、光学、光电子学、热学以及生物学等方面表现出许多新奇的现象，为科学、工程和技术的发展提供了新的契机。 随着现代实验技术的发展，越来越多的半导体纳米簇被成功研制出来，但无法从实验上获得这些团簇的几何和电子结构的全面微观信息，因此理论研究成为获得团簇结构信息最有效的途径，尤其是基于密度泛函理论的计算，可以对中等尺寸的体系得到精确度相当高的计算结果。目前，团簇的理论研究，一方面是针对小的团簇开展基础性的研究，探索随着团簇尺寸的增大，团簇如何从结构和特性上向体材结构演化。另一方面，是对团簇材料的研究，目的在于发现和预测特殊材料的特殊性质，从而对功能材料进行理论设计，推动纳米团簇材料的发展。 基于以上两点，本文利用密度泛函理论方法，对一系列碳、硅、硼为基的混合半导体团簇，按照“由小到大逐级生长”的方法，从理论上设计和预测了它们的几何和电子结构，寻找了这些团簇的基本结构单元、成键规则和生长机制。同时，对于B和A1原子掺杂的碳纳米管团簇材料，在原子和分子水平上研究了它们对若干气体小分子的气敏性能，探讨了有关的微观作用机理，获得了控制其气敏性的关键因素，为相关的实验研究提供了一定的理论指导。 本文得到的主要创新性结果如下： 一、预测了碳硅富勒烯存在的可能性，并提出了通过在硅结构中均匀掺杂碳原子来稳定硅笼的新方法。 富勒烯和纳米管在自然界中通常是共生的，均匀杂化排列的碳化硅纳米管已经被成功合成，但碳硅富勒烯的结构尚未见报道。本文第二章设计了一系列新的无机富勒烯硅碳笼，（SiC）ⁿ（n=6-36），这些笼由均匀杂化排列的Si-C四元环和六元环组成。在B3LYP／LANL2DZ和B3LYP／6-31G（d）水平上研究了这些笼的几何更多还原

【Abstract】 The discovery of C₆₀ molecule by Kroto et al in 1985 and subsequent synthesis of carbon nanotubes by Iijima in 1991 have opened new research opportunities in science, engineering, and technology. Since then, semiconductor clusters, in particular, based on silicon, carbon, boron, have been received much attention, for their novel qualities in electronics, optics, calorifics, even biology.In view of that more and more semiconductor clusters have been synthesized successfully, we can’t obtain full information about the geometries and electronic qualities from the experiments, while theoretical methods become the most effective approach to study clusters. So in this paper, we study a series of semiconductor clusters containing silicon, carbon and boron in order to discover their ground state structures and the growth mechanisms as well as the building blocks, to design and predict the new clusters with certain special functional materials. On the other hand, we study the special qualities for larger nanocluster materials, such as carbon nanotubes （CNT） doped by B or Al atom as gas sensers in order to direct experiments.Now, we have obtained plentiful and substantial conclusions derived as follows:1. The present calculations not only indicate that silicon-carbon fullerenes are promised to be synthesized in future, but also provide a new way for stabilizing silicon cages by uniformly doping carbon atoms into silicon structures.It is well known that the fullerenes and nanotubes are generally concomitant with each other in the nature. In view of the fact that the SiC nanotubes have been synthesize successfully, （SiC）_n cages are expected to exist in a large family, similar to carbon fullerenes. So in the present work we proposed a series of silicon-carbon cagelike structures, （SiC）_n （n=6-36）, based on the C and Si uniformly hybrid four- （4MRs） and six-membered rings （6MRs）. As far as we known, this is the first study of SiC fullerenes. Their geometrical and electronic structures, as well as the relative stabilities were investigated systematically using the density functional theory. Our calculations indicate that all SiC cages proposed here present highly structural更多还原