Surface chemistry and growth manipulation of supported metal clusters and hybrid nanostructured materials

了解表面上发生的化学过程对许多科学和技术领域至关重要，包括化学和石化技术、环境科学、材料研究、分子电子学和纳米技术。提出的工作旨在研究发生在新型衬底上的表面化学和物理，从支撑在单晶硅表面的金属团簇（几个原子到几纳米大小）到透明导电氧化物（例如氧化锡）的纳米结构。我们的研究将集中在具有生物化学意义的吸附剂上，并将跟踪它们在这些底物上的吸附以及在热和低能电子的刺激下结构和电子性质的演变。使用允许我们一次精确沉积一个原子或分子的专用工具（即分子束外延），我们将开发适当的生长策略，以获得这些金属团簇在硅衬底上的近单尺寸分布。利用激光烧蚀技术，我们还将能够构建各种透明导电氧化物的一维和二维纳米结构。这些新型纳米材料不仅将为研究在其复杂表面上发生的基本过程提供重要的实验平台，而且还将作为开发催化、生物传感、缓释药物输送、太阳能电池器件和单纳米结构电子学等新兴应用的基础平台。我们将重点关注三个一般感兴趣的领域：(1)金属团簇的生长，特别强调硅载体上的初始成核位置如何影响团簇的几何形状和结构；(2) DNA碱基分子与金属簇的相互作用与簇大小的关系；(3)双金属系统（纳米合金）和透明导电氧化物的混合纳米结构的生长操纵，它们分别对纳米催化和纳米磁学应用以及太阳能电池应用感兴趣。

Understanding the chemical processes occurring on surfaces is fundamentally important to many areas of science and technology, including chemical and petrochemical technologies, environmental science, materials research, molecular electronics, and nanotechnology. The proposed work seeks to study the surface chemistry and physics occurring on novel substrates, from metallic clusters (of a few atoms to a few nanometers in size) supported on single-crystal silicon surfaces to nanostructures of transparent conductive oxides (e.g. tin oxide). Our study will focus on adsorbates of biochemical interest, and will follow the evolution of their structures and electronic properties upon adsorption on these substrates and upon stimulation with heat and low-energy electrons. Using specialized tools that allow us to precisely deposit one atom or molecule at a time (i.e. molecular beam epitaxy), we will develop the appropriate growth strategies to obtain a near-monosized distribution of these metal clusters on the silicon substrate. Using a laser ablation technique, we will also be able to build a variety of one-dimensional and two-dimensional nanostructures of transparent conductive oxides. These novel nanomaterials will not only provide important test beds for investigating fundamental processes occurring on their complex surfaces, but also serve as the basic platforms for developing emerging applications in catalysis, biosensing, extended-release drug delivery, solar cell devices and single-nanostructure electronics. We will focus on three general areas of interest: (1) Growth of metal clusters, with special emphasis on how the initial nucleation sites on the silicon support will affect the geometries and structures of the clusters; (2) Interactions of DNA base molecules with metal clusters as a function of cluster size; and (3) Growth manipulation of hybrid nanostructures of bimetallic systems (nanoalloys) and of transparent conductive oxides that are of respective interest to nanocatalysis and nanomagnetics applications and to solar cell applications.