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

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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.