NSF-EC Activity: Nanometer Scale Induced Structure Between Amorphous Layers and Crystalline Materials

这项实验和计算相结合的工作研究了稳定的晶间薄膜的新性质。稳定的薄膜具有纳米级的结构和组成，这作为体相是不稳定的，因此可以具有体相中找不到的物理特性。例如，晶间薄膜的介电常数和观察到的原子结构不能从体相行为中推断出来。此外，一些通常由工程过程定制的物理属性，如薄膜宽度，变成了平衡量，这些量自然是均匀的，并随成分高度可调。它们的稳定性被认为与它们附近的晶体材料诱导到它们的分子结构中的剩余有序有关；我们寻求在硅酸盐和钛酸盐系统中对这些薄膜进行实验表征，并找到理论和计算模型来分类它们的行为。薄膜将以受控成分进行处理，并用综合实验技术(EXAFS、EXELFS、ELNES、VEELS和VUV光谱以及HREM)进行表征。模型将结合从头算、密度泛函理论、OLCAO、分子动力学和界面热力学来开发并与实验相关联。新技术设备的生产往往依赖于新材料的开发或产生新性能的材料的新加工方法。随着设备越来越小，对精确的材料特性的需求也越来越大-以及更多的技术回报。在一些材料中，例如我们研究的硅酸盐和钛酸盐，材料的性质随着材料系统的大小(即设备中的材料及其结构)的缩小而发生急剧变化。这些变化可能会对我们增强和控制属性的能力产生深远影响。例如，非常薄的薄膜的电子性质可以针对特定的器件进行修改，而由于其小尺寸的物理效应，我们设计这些薄膜的能力可能会增强。我们将尝试用综合的实验、理论和计算方法来描述和理解这些效应。我们希望我们的成果可以直接用于提高现有电子设备的性能，我们的研究可能会阐明导致新技术生产的特定材料特性。本提案是应国家科学基金会和欧盟委员会之间的材料科学合作活动建议：NSF(00-18)“的征集而提交的。

This combined experimental and computational effort investigates novel properties of stable intergranular films. Stable films have nanoscale structures and compositions which would not be stable as a bulk phase and, therefore, can have physical properties that are not found in bulk phases. For instance, the dielectric constant and the observed atomic structure of the intergranular films cannot be extrapolated from bulk behavior. Furthermore, some physical attributes that are normally tailored by engineering processes, such as film width, become equilibrium quantities that are naturally uniform and highly tunable with composition. Their stability is assumed to be associated with remnant order induced into their molecular structure from the crystalline materials proximate to them; we seek to characterize experimentally these films in silicate and titanate systems and find theoretical and computational models to categorize their behavior. The thin films will be processed with controlled composition and characterized by combined experimental techniques (EXAFS, EXELFS, ELNES, VEELS and VUV spectroscopies, and HREM). Models will be developed and correlated with experiments by combined ab-initio, density functional theory, OLCAO, molecular dynamics, and interface thermodynamics.%%%The production of new technological devices often depends on the development of a novel material or a new way to process materials that generate novel properties. With ever smaller devices, there is an increased demand on precise material properties---as well as an increased technological reward. In some materials, such as the silicates and titanates we investigate, the properties of materials undergo acute changes as the size of the material system (i.e. the materials and their architecture within a device) shrinks. These changes can have profound effects on our ability to enhance and control properties. For instance, the electronic properties of very thin films may be modified for particular devices and our ability to engineer them may be enhanced due to the physical effects of their small size. We will attempt to characterize and understand these effects with an integrated experimental, theoretical, and computational approach. We expect that our results may used directly to enhance the properties of existing electronic devices and that our research may illuminate specific material properties that result in the production of new technologies.This proposal was submitted in response to the solicitation "Proposals for Cooperative Activities in Materials Sciences between the National Science Foundation and the European Commission: NSF (00-18)".