Electronic structure and optical properties of transition metal doped silicon clusters on surfaces - Building blocks for cluster assembled materials

掺杂半导体团簇由于其独特的性质，很有可能成为构建团簇组装材料的候选材料。通过掺杂过渡金属原子，可以将小的硅团簇稳定在面内笼状结构中，具有极好的稳定性。这些团簇的特征是大的最高占据{最低未占据分子轨道(HOMO-LUMO)能隙，电子壳层闭合，以及围绕掺杂原子的硅笼。根据理论预测，HOMO-LUMO能隙可以通过改变掺杂原子和主团簇的大小来控制。甚至有实验证据表明，在团簇表面没有悬挂键的无氢掺杂硅团簇。在这个项目中，我们旨在了解过渡金属掺杂的硅团簇MSin(M=Cr，Ti，W；n&lt；20)在金属和半导体衬底上沉积后的电子和光学性质。我们将把重点放在具有化学稳定性的特殊“魔力”团簇上，这些团簇适合作为团簇组装材料的构建块。这些团簇将在实验室中用光致发光和光电子能谱进行研究，同时在同步加速器存储环上进行X射线吸收光谱研究。通过这些方法，我们将阐明团簇光致发光的基本问题和与技术相关的团簇表面稳定性问题，以及沉积团簇中可能的电致发光。

Because of their fascinating properties, doped semiconductor clusters are promising candidates as building blocks for cluster assembled materials. By doping with transition metal atoms, small silicon clusters can be stabilized in endohedral cage structures with exceptional stability. These clusters are characterized by large highest occupied{lowest unoccupied molecular orbital (HOMO-LUMO) gaps, electronic shell closures, and a silicon cage surrounding the dopant atom. According to theoretical predictions, the HOMO-LUMO gap can be controlled by varying both the dopant atom and the host cluster size. There is even experimental evidence of hydrogen-free doped silicon clusters with no dangling bonds at the cluster surface. In this project, we aim at an understanding of the electronic and optical properties of transition metal doped silicon clusters MSin (M=Cr, Ti, W; n < 20) after deposition onto metal and semiconductor substrates. We will focus on special `magic' clusters with chemical stability, which are suited as building blocks for cluster assembled materials. These clusters will be studied by photoluminescence and photoelectron spectroscopy in the laboratory, accompanied by X-ray absorption spectroscopy at synchrotron storage rings. With these methods, we will clarify fundamental issues of cluster photoluminescence and technologically relevant questions of cluster stability on surfaces, as well as possible electroluminescence in deposited clusters.