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

技术：这项研究为纳米尺度的原子有序化提供了新的见解，它与非晶态材料中的缺陷和缺陷聚集的联系，以及纳米尺度有序和缺陷对性能的影响。该项目是一项合作的重点研究项目(FRG)，旨在解决：(1)硫化物玻璃中纳米级结构与组成的函数关系，目标是建立中间相的详细模型；(2)导致硫化物玻璃中光变黑和光熔化的光学驱动的纳米级结构转变；(3)纳米级有序对非晶态过渡金属二硼化物薄膜热稳定性和相变的影响；以及(4)非晶态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导致的空间不均匀缺陷分布所调节的。硫系化合物除了是典型的玻璃形成网络外，还在光子学中有重要的应用。中间相组成区域中的几个玻璃表现出极高的克尔光学非线性，正在被研究用于全光开关。光变暗使波导和衍射栅的制作变得容易。金属硼化物是硅微电子金属化的候选扩散势垒，这是在极薄的薄膜中低杂质扩散和高热稳定性的必要条件。对上述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非晶态材料结构分析的新范式，在这种范式中，人们使用散射探针来表征从最近邻到几纳米的样品的结构和化学，然后使用建模技术来合成与关于特定材料的已知信息一致的原子结构模型。然后对该模型进行研究，以进一步阐明材料的结构和性质。关键的创新是来自实验数据合成的涨落电子显微镜的纳米级结构信息，以及具有实验约束的分子弛豫的从头算能量学。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。这一努力还为在多学科的协作环境中培训学生和博士后提供了一个难得的机会，这种环境处于材料中实验和计算工具集成的前沿。该项目还包括旨在加强代表人数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.