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.
