The Stability of Phases in Thin Multilayered Films

多层薄膜中相的稳定性

• 批准号: 1207220
• 负责人: Gregory Thompson
• 金额: $ 37.5万
• 依托单位: University of Alabama Tuscaloosa
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2012
• 资助国家: 美国
• 起止时间: 2012-08-15 至 2016-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1207220&HistoricalAwards=false
• 关键词: Stability; Phases; Thin; Multilayered; Films

TECHNICAL SUMMARY:Materials in structures with large surface area-to-volume ratios can exhibit size dependent physical and chemical properties that are different than their bulk form. These changes can be related to crystallographic transformations to new phases called pseudomorphs. This research will elucidate the underpinnings of this phase stability behavior by providing a systemic study using multilayered thin film architectures. Model metallic systems whose length scales and compositions can be controlled with near atomic processing precision will allow the influence of lattice misfit, layer thickness, and composition on pseudomorphic phase formation and stability to be determined. Real-time, in situ thin film growth stresses of these materials will be measured and correlated to the interfacial stress evolution. Molecular Dynamics (MD) simulations will be used to explore the kinetics of pseudomorphic formation during deposition, merging experiments with modeling. These results will be related to post-growth structural and chemical characterization of the phases and interfaces. The program will be able to delineate how intrinsic film stress drives compositional intermixing across interfaces which can thermodynamically promote phase transformations. Classical thermodynamics will be used to predict and explain phase stability criteria. The results will be developed within the framework of a predictive phase diagram, where length scale is a state variable similar to temperature and pressure used in traditional metallurgy phase diagrams, in determining phase transition regions. NON-TECHNICAL SUMMARY:When material sizes become very small, a material can alter how it arranges its atoms within its structure. This atomic rearrangement often results in changes in the materials properties such as its electrical conduction, its optical appearance or its physical strength. Too often these atomic rearrangements are serendipitously discovered. This research aims at developing a predictive diagram to let scientists understand when atomic rearrangements occur as a function of size. The results will provide maps on how to predict and engineer atomic structure for ever decreasing material sizes. Through this grant, the technical workforce of the United States will be grown. This will be achieved through the education of graduate and one post-doctoral students. These individuals will engage industry through their interaction in the multi-disciplinary research center, Materials for Information Technology (MINT) situated on the campus of the University of Alabama (UA). In addition, the program will engage local Alabaman high school students through the Nanoscience and Engineering High School Research Internship Program, successfully initiated during the principle investigator?s NSF Career award. Materials education efforts during this grant will be broadened to include instruction to middle and high school teachers through summer camps held on the campus of UA. By directly educating secondary education teachers on how to incorporate materials examples in their classroom, the impact of materials education will engage a broader and more diverse number of students.

技术摘要：具有大表面积与体积比的结构中的材料可以表现出与其本体形式不同的依赖于尺寸的物理和化学特性。这些变化可能与晶体转变为称为假晶的新相有关。这项研究将通过使用多层薄膜架构进行系统研究来阐明这种相稳定性行为的基础。 其长度尺度和成分可以以接近原子加工精度控制的模型金属系统将允许确定晶格失配、层厚度和成分对假晶相形成和稳定性的影响。这些材料的实时原位薄膜生长应力将被测量并与界面应力演变相关联。 分子动力学 (MD) 模拟将用于探索沉积过程中假晶形成的动力学，将实验与建模相结合。 这些结果将与相和界面的生长后结构和化学特征相关。该程序将能够描述内在薄膜应力如何驱动跨界面的成分混合，从而在热力学上促进相变。经典热力学将用于预测和解释相稳定性标准。结果将在预测相图的框架内开发，其中长度尺度是类似于传统冶金相图中使用的温度和压力的状态变量，用于确定相变区域。非技术摘要：当材料尺寸变得非常小时，材料可以改变其原子在其结构内的排列方式。这种原子重排通常会导致材料特性的变化，例如导电性、光学外观或物理强度。这些原子重排常常是偶然发现的。这项研究的目的是开发一个预测图，让科学家了解原子重排何时发生作为大小的函数。研究结果将提供如何预测和设计原子结构以适应不断减小的材料尺寸的地图。通过这笔赠款，美国的技术劳动力将得到增长。这将通过研究生和一名博士后学生的教育来实现。这些人将通过在位于阿拉巴马大学 (UA) 校园的信息技术材料 (MINT) 多学科研究中心的互动来参与行业。此外，该计划还将通过纳米科学与工程高中研究实习计划吸引当地阿拉巴曼高中学生，该计划在首席研究员获得国家科学基金会职业奖期间成功启动。这笔赠款期间的材料教育工作将扩大到包括通过在阿布扎比大学校园举办的夏令营对初中和高中教师进行指导。通过直接教育中学教师如何将材料示例融入课堂，材料教育的影响将吸引更广泛、更多样化的学生。