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

这一结合实验和计算的努力研究了稳定的晶间膜的新特性。稳定膜具有纳米级的结构和成分，这些结构和成分不像体相那样稳定，因此可以具有体相中没有的物理性质。例如，介电常数和观察到的晶间膜的原子结构不能从体行为推断出来。此外，一些通常由工程过程定制的物理属性，如薄膜宽度，成为自然均匀且随成分高度可调的平衡量。它们的稳定性被认为与从接近它们的晶体材料诱导到其分子结构中的残余秩序有关；我们试图通过实验表征这些膜在硅酸盐和钛酸盐体系中，并找到理论和计算模型来分类它们的行为。薄膜将在控制成分的情况下进行处理，并通过组合实验技术（EXAFS， EXELFS， ELNES， VEELS和VUV光谱以及HREM）进行表征。将结合从头算、密度泛函理论、OLCAO、分子动力学和界面热力学建立模型并与实验相关联。新技术设备的生产通常取决于新材料的开发或新方法的加工，从而产生新的性能。随着设备越来越小，对精确材料性能的要求也越来越高，技术回报也越来越高。在某些材料中，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尺寸（即材料及其在设备内的结构）的缩小而发生急剧变化。这些变化会对我们增强和控制属性的能力产生深远的影响。例如，非常薄的薄膜的电子特性可以为特定的设备进行修改，并且由于其小尺寸的物理效应，我们设计它们的能力可能会增强。我们将尝试用综合实验、理论和计算方法来描述和理解这些效应。我们期望我们的研究结果可以直接用于增强现有电子设备的性能，并且我们的研究可以阐明导致新技术生产的特定材料特性。该提案是响应“美国国家科学基金会和欧洲委员会材料科学合作活动提案：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)".