Experimental observations of twin formation during thermal annealing of nanocrystalline copper films using orientation mapping

This study employed a TEM-based automated crystal orientation mapping technique that enables orientation mapping with nanoscale spatial resolution. This nanoscale orientation mapping technique was employed to study thermally-assisted grain growth and to quantify the attendant formation of nanotwins and twin junctions in nanocrystalline Cu. The grain size increased from 29 ± 14 nm to 57 ± 22 nm and the fraction of twin-containing grains increased from 0.18 to 0.70. Close inspection of the twins and twin junctions captured within orientation maps documented a frequency of junctions that was remarkably consistent with previous molecular dynamics predictions.