Dislocation Nucleation and Patterning in Thin Layered Materials: Deformation and Fracture Mechanisms

技术方面：很明显，21世纪将见证前所未有的技术进步：信息技术、纳米技术、生物技术等等。这些新发展的一个共同特点是硬件的小型化。为了在许多新兴技术中继续小型化的趋势，需要在越来越小的长度尺度上利用材料的行为。本研究项目旨在解决与薄层材料的变形和破坏有关的基本科学和技术问题，特别是在受限的薄金属薄膜中的位错活动。在本研究中，将开发能够加载小尺寸样品的实验技术。透射电子显微镜结合FIB试样制备将用于确定位错构型及其在受限金属薄层中的演变。通过测量界面断裂韧性来评价位错对界面粘附和界面裂纹扩展的影响。进行了离散位错动力学模拟，以确定界面破坏的临界条件，包括临界位错模式和界面性质。非技术：本研究将显著增强对薄层材料系统中位错成核和图案化的基础知识，增强对位错活动对界面粘附和裂纹扩展影响的理解，并有助于确定薄层材料中失效的主要机制。这些基本的理解将对微电子和MEMS行业的产品设计和开发产生重大影响。该项目还包括一个全面的学者交流和教育计划。学者交流计划包括通过电话和互联网定期召开研究会议，以及PI与德国斯图加特马克斯普朗克研究所的德国合作者之间的年度互访。此外，PI和德国研究人员将共同指导从事该项目的美国和德国研究生，以便学生能够接触到美国和德国机构的研究活动。这种国际交流活动的更大目标是培养和造就既具有扎实的材料科学与工程知识，又具有丰富国际经验的新一代工程专业学生。

TECHNICAL: It has become clear that the 21st century will witness unparalleled progress in technologies: information technology, nanotechnology, biotechnology, to name a few. A common feature of many of these new developments is the miniaturization of hardware. To continue the trend of miniaturization in many emerging technologies, the behavior of materials at an increasingly smaller length scale needs to be harnessed. This research project is to address the fundamental scientific and technical issues associated with deformation and failure of thin-layered materials, in particular the dislocation activities in confined, thin metal films. In this study, experimental techniques that enable loading of small-scale specimens will be developed. TEM combined with FIB specimen fabrication will be used to determine the dislocation configurations and their evolution in confined metal thin layers. The effects of dislocations on interface adhesion and interfacial crack propagation are evaluated by measuring interfacial fracture toughness. Discrete dislocation dynamics simulations are conducted to identify critical conditions, including critical dislocation patterns and interface properties, for interfacial failure. NON-TECHNICAL: This study will significantly enhance the fundamental knowledge on dislocation nucleation and patterning in thin-layered material systems, enhance the understanding of the effects of dislocation activities on interfacial adhesion and crack propagation, and help identify the dominant mechanisms of failure in thin-layered materials. Such fundamental understanding will have significant impact on product design and development in microelectronics and MEMS industry. The project also contains a comprehensive scholar exchange and educational plan. The scholar exchange plan includes regular research meetings by phone and via the Internet, and annual mutual visits between the PI and the German collaborator at the Max Planck Institute in Stuttgart, Germany. Furthermore, the PI and the German researcher will co-advise U.S. and German graduate students working on the project so that the students are exposed to research activities at both U.S. and German institutions. Such international exchange activities serve the broader objective of training and producing a new generation of engineering students with not only solid knowledge in materials science and engineering, but also extensive international experiences.