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，成为团簇组装材料的重要组成部分。通过掺杂过渡金属原子，小硅团簇可以稳定在具有异常稳定性的笼形结构中。这些簇的特征在于大的最高占据（最低未占据）分子轨道（HOMO-LUMO）间隙、电子壳层闭合和围绕掺杂剂原子的硅笼。根据理论预测，HOMO-LUMO能隙可以通过改变掺杂剂原子和主体团簇尺寸来控制。甚至有实验证据表明，无氢掺杂的硅簇在簇表面没有悬挂键。在这个项目中，我们的目标是了解过渡金属掺杂的硅团簇MSin（M=Cr，Ti，W; n < 20）沉积到金属和半导体衬底上后的电子和光学性质。我们将专注于具有化学稳定性的特殊“魔法”簇，这些簇适合作为簇组装材料的构建块。将在实验室中通过光致发光和光电子能谱研究这些团簇，同时在同步加速器储存环上进行X射线吸收光谱研究。通过这些方法，我们将澄清团簇光致发光的基本问题和表面上团簇稳定性的技术相关问题，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.