The Behaviour of Grain Boundaries in Nanocrystalline Metal Films.

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• Professor John Boland, Centre for Research on Adaptive Nanostructures and Nanodevices (CRANN), Trinity College, Dublin
• Friday 07 June 2019, 10:00-11:00
• Maxwell Centre, Rayleigh Seminar Room.

If you have a question about this talk, please contact Kirsty Shepherd.

This talk discusses on the properties of nanocrystalline metal films, with a particular emphasis on copper. Scanning tunneling microscopy and simulations are used to visualize for the first time the 3D structure of grain boundaries (GBs) that emerge at the surface of nearly coplanar copper nanocrystalline (111) films. Remarkably, we observe that low angle dissociated GBs are found exclusively at valley and ridge locations. This behavior is the result of a GB energy minimization phenomenon that involves the formation of wide kink-free stacking fault ribbons, made possible by the rotation of dislocation lines along the boundary and the commensurate tilting of the adjoining grains (Science 357, 397-400 (2017)). In the case of high angle boundaries the GB core is expected to be perpendicular to the film surface and comprised of so-called structural units. However, both experiment and simulation support the reconstruction of the GBs as it approaches the surface to form a dissociated structure, reminiscence of lowangle behavior. In contrast, high angle GBs shows the presence of both local and global curvature, the local behavior mapping closely onto that seen for lower angles. We show that this behavior is in part due to the influence of the triple junction and leads to surface and size effects that should have implications for corrosion, transport and other GB mediated processes.

This talk is part of the Electrical Engineering series.

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• Electrical Engineering
• Maxwell Centre, Rayleigh Seminar Room

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