Advances in Experimental Studies of Grain Growth in Thin Films

In this article, we review recent developments in the experimental study of grain growth in nanocrystalline metallic thin films, emphasizing transmission electron microscopy-based imaging and orientation mapping techniques and highlighting useful experimental and data analytical frameworks for dynamic experiments. Studies of grain growth have fallen short of the scale required to fully characterize the coarsening process, and models still fail to fully capture the true behavior of grain growth in polycrystalline systems as they pertain to geometric, topological and crystallographic metrics. Moreover, existing grain growth studies are either coarse in time and temperature or otherwise limited in scope. Nevertheless, important observations such as the stagnation of thin film grain growth at a universal grain size distribution and the strong correlations between the grain boundary character distributions in thin film and bulk materials motivate larger-scale dynamic studies. Additionally, recent hardware and software advances have removed bottlenecks to large-scale and in situ data acquisition via (1) automated grain boundary segmentation in micrographs, (2) low thermal mass microelectromechanical systems and (3) integrated hardware-software drift correction and data management solutions. We argue that these innovations render thin films a key integrated experimental platform for the next generation of grain growth studies.