The Synthesis, Characterization, and Surface Chemistry of Ultra-thin Oxide Films

摘要 9423707 该项目的目标是合成，表征和表面化学的定义，超薄（小于10纳米）氧化膜。超薄氧化膜将在耐火单晶衬底上制备，并使用一系列表面科学技术进行表征，包括低能电子衍射、俄歇电子能谱、X射线和紫外光电子能谱、离子散射能谱、反射吸收傅里叶变换红外能谱、高分辨率电子能量损失能谱、扫描隧道显微镜/原子力显微镜和程序升温脱附。有序的，薄膜形式的氧化物表面将在单晶，折射金属基板上制备。这种方法将扩展到包括各种氧化物和混合氧化物类型。利用这些高度有序，化学计量的氧化物薄膜的方法提供了一个有前途的新策略，研究这些材料的表面化学的方式排除利用散装材料和传统技术。 这项研究影响了氧化物的基础科学和各种实用技术，如环境废物修复，设备制造和催化。由于许多氧化物材料的高度绝缘性质，它们的表面几何和电子性质通常比例如金属表面受到少得多的关注。迄今为止，氧化物材料的化学吸附和催化性能的广泛工作已经进行，然而，发生在氧化物表面上的微观反应机制仍然没有很好地理解。其主要原因是这些研究主要针对粉末样品进行。 因此，该信息表示除了在粉末样品中不可避免地存在的各种缺陷之外暴露的各种晶面的平均值。另一方面，许多氧化物材料的高纯度单晶难以获得，并且这些绝缘材料的研究经常遇到与表面充电、样品加热和清洗相关的困难。因此，显然需要合成高质量的薄氧化物膜。氧化物材料的结构和化学吸附性质可以通过制备定义明确的薄氧化物膜来获得，其性质与其单晶体对应物相同，从而便于在受控条件下对这些材料进行表面化学研究。

Abstract 9423707 The goal of this project is the synthesis, characterization, and surface chemistry of well defined, ultra-thin (less than 10 nm) oxide films. Ultra-thin oxide films will be prepared on refractory single crystal substrates and characterized using an array of surface science techniques, including low energy electron diffraction, Auger electron spectroscopy, X-ray and ultraviolet photoelectron spectroscopy and, ion scattering spectroscopy, reflection absorption Fourier transform infrared spectroscopy, high resolution electron energy loss spectroscopy, scanning tunneling microscopy/atomic force microscopy, and temperature programmed desorption. Ordered, oxide surfaces in thin film form will be prepared on single-crystal, refractor metal substrates. This approach will be extended to include a variety of oxide and mixed-oxide types. A methodology utilizing these highly ordered, stoichiometric oxide thin films offers a promising new strategy for studying the surface chemistry of these materials in ways precluded utilizing the bulk materials and traditional techniques. %%% This study impacts the basic science of oxides and various practical technologies such as environmental waste remediation, device fabrication, and catalysis. Because of the highly insulating nature of many oxide materials, their surface geometrical and electronic properties, in general, have received much less attention than, for example, metal surfaces. To date, extensive work on the chemisorption and catalytic properties of oxide materials have been conducted, however, the microscopic reaction mechanisms occurring on oxide surfaces are still not well understood. The principle reason for this is that these studies have been performed primarily on powder samples. Therefore, the information represents an average of the various crystal faces exposed in addition to a variety of defects which are inevitably present in the powdered samples. On the other hand, high-purity single cr ystals of many oxide materials have been difficult to obtain and studies of these insulating materials have often encountered the difficulties associated with surface charging, sample heating and cleaning. Therefore, there is a clear need for the synthesis of high quality, thin oxide films. Structural and chemisorptive properties of oxide materials can be obtained by preparing well-defined, thin oxide films whose properties are identical to their single-crystal bulk counterparts, thereby facilitating surface chemical studies of these materials under controlled conditions.