Stresses, Deformation, and Dislocations in Thin Films: Combining Modeling and Simulations with Experiments

在这项资助下，位错动力学模拟和透射电子显微镜将被用来研究衬底上金属薄膜中位错的行为。该程序的一个主要目标是模拟边界和界面附近位错集合的细观行为，以便与使用基片曲率和X射线方法测量的整体力学行为进行比较。该程序既包括自下而上的研究，其中检查相互作用的位错对所采用的构型和这些相互作用的强度，也包括模拟许多位错的行为以寻找控制机制的自上而下的研究。这种实验和模型的结合有望提供导致薄膜中非块状行为的机制的直接证据。这项工作的目的是详细研究导致金属薄膜高应力和非块状行为的位错机制。这种薄膜是各种纳米器件中不可缺少的元件，但通常承受着非常高的应力，可能会因变形、空洞形成或断裂而导致失效。薄膜的力学行为不同于块体材料，也没有得到很好的了解。在这个项目中，位错动力学模拟将被用来研究薄膜的尺寸约束如何影响位错行为和力学性质。在模拟中看到的位错组态将与用透射电子显微镜实验观察到的位错组态进行比较。这种实验和建模的独特结合将提供对薄膜金属化的力学行为的更好的理解。该项目将支持以高中教师和学生为重点的外展努力，并将吸引本科生参与研究。

Under this grant, dislocation dynamics simulations and transmission electron microscopy will be used to study the behavior of dislocations in thin metal films on substrates. A major objective of the program is to simulate meso-scale behavior of ensembles of dislocation near boundaries and interfaces for comparison with the overall mechanical behavior measured using substrate curvature and x-ray methods. The program includes both a 'bottom-up' study in which the configurations adopted by interacting pairs of dislocations and the strength of those interactions are examined, and a 'top down' study in which the behavior of many dislocations is simulated to search for controlling mechanisms. This combination of experiments and modeling is expected to provide direct evidence of mechanisms that lead to non-bulk-like behavior in thin films. The goal of this work is to study the dislocation mechanisms that lead to high stresses and non-bulk-like behavior in thin metal films in detail. Such films are indispensable elements in a wide range of nanofabricated devices, but typically suffer from very high stresses, which may lead to failure by deformation, void formation, or fracture.The mechanical behavior of thin films is not like that of bulk materials and is not well understood. In this program, dislocation dynamics simulations will be conducted to study how the dimensional constraints of a thin film affect dislocation behavior and mechanical properties. Dislocation configurations seen in simulations will be compared with those observed experimentally using transmission electron microscopy. This unique combination of experiments and modeling will provide a better understanding of the mechanical behavior of thin film metallizations. The project will support outreach efforts focused on high school teachers and students, and will engage undergraduates in research.