FRG: Nanoscale Structural Order in Amorphous Materials and its Relation to Diffusion and Electronic Defects

技术支持：这项研究提供了新的见解纳米级原子有序，其连接到缺陷和缺陷聚集在非晶材料，以及纳米级的顺序和缺陷对性能的影响。该项目是一个合作的重点研究项目（FRG），并解决：（1）纳米结构作为硫属化物玻璃中的组成的函数，目标是建立一个详细的中间相模型;（2）光学驱动，纳米结构转换，导致硫属化物玻璃中的光暗化和光熔融;（3）纳米尺度对非晶过渡金属二硼化物薄膜热稳定性和相变的影响;以及（4）非晶二硼化物中杂质扩散与纳米级有序之间的联系，这可能是由纳米级有序引起的空间非均匀缺陷分布所介导的。除了作为典型的玻璃形成网络之外，硫属化合物在光子学中也有重要的应用。在中间相组成区域中的几种玻璃表现出极高的克尔光学非线性，正在研究用于全光开关。光暗化使得波导和衍射光栅的制造变得容易。金属二硼化物是硅微电子金属化的候选扩散阻挡层，对于极薄的薄膜来说，低杂质扩散和高热稳定性是必不可少的。以上四个问题的研究将为这些应用奠定基础材料科学基础。非技术性：这项研究合作的主要影响是建立了一种新的范式，用于非晶材料的结构分析，其中使用散射探针来表征样品的结构和化学性质，从最近的邻居到几个纳米，然后使用建模技术来合成与已知的特定材料一致的原子结构模型。然后研究该模型以进一步阐明材料的结构和性质。关键的创新是纳米结构信息的波动电子显微镜包括在合成实验数据和从头算能量与实验约束的分子弛豫。该项目将提供可下载的手册、计算机代码，并利用技术会议在科学界广泛传播这些工具，这些工具最终将用于解决广泛的材料科学问题。这项工作还为学生和博士后在多学科协作环境中的培训提供了一个难得的机会，该环境处于材料中实验和计算工具整合的最前沿。该项目还包括旨在加强代表性不足的群体参与科学和工程的活动。

TECHNICAL: This research offers new insights into nanoscale atomic ordering, its connection to defects and defect clustering in amorphous materials, and the influence of nanoscale order and defects on properties. The project is a collaborative focused research project (FRG), and addresses: (1) nanoscale structure as a function of composition in chalcogenide glasses with the goal of building a detailed model of intermediate phases; (2) optically-driven, nanoscale structural transformations that cause photodarkening and photomelting in chalcogenide glasses; (3) influence of nanoscale order on thermal stability and phase transformations of amorphous transition metal diboride thin films; and (4) connection between impurity diffusion and nanoscale order in amorphous diborides, which may be mediated by a spatially non-uniform defect distribution caused by nanoscale order. The chalcogenides have important applications in photonics in addition to being prototypical glass-forming networks. Several glasses in the intermediate phase composition region exhibit extremely high Kerr optical non-linearities that are being investigated for all-optical switching. Photodarkening enables easy fabrication of waveguides and diffraction gratings. The metal diborides are candidate diffusion barriers for silicon microelectronic metallizations, for which low impurity diffusion and high thermal stability in extremely thin films are essential. Research on the four problems above will lay basic materials science groundwork for these applications. NONTECHNICAL: A primary impact of this research collaboration is establishment of a new paradigm for the structural analysis of amorphous materials, in which one uses scattering probes to characterize the structure and chemistry of a sample from nearest-neighbors to a few nanometers, then uses modeling techniques to synthesize an atomistic structural model consistent with what is known about the particular material. That model is then studied to further elucidate the structure and properties of the material. Key innovations are nanoscale structural information from fluctuation electron microscopy included in synthesis of experimental data and ab initio energetics with experimentally constrained molecular relaxation. The project will provide downloadable manuals, computer code and make use of technical meetings to disseminate these tools broadly in the scientific community, where they will eventually be used to address a wide range of materials science problems. The effort also provides an exceptional opportunity for the training of students and post-docs in a multidisciplinary, collaborative environment that is at the forefront of the integration of experimental and computational tools in materials. The project also includes activities designed to enhance participation of underrepresented groups in science and engineering.