In situ TEM study of grain growth in nanocrystalline copper thin films

Abstract

Nanocrystalline metals demonstrate a range of fascinating properties, including high levelsof mechanical strength. However, as these materials are exposed to high temperatures, it iscritical to determine the grain size evolution, as this process can drastically change themechanical properties. In this work, nanocrystalline sputtered Cu thin films with43 ± 2 nm grain size were produced by dc-magnetron sputtering. Specimens weresubsequently annealed in situ in a transmission electron microscope at 100, 300 and500 °C. Not only was grain growth more evident at500 °C but also the fraction of twins found. An analysis of grain growthkinetics revealed a time exponent of 3 and activation energy of 35 kJ mol − 1. This value is explained by the high energy stored in the form of dislocation, grainboundaries and twin boundaries existing in nanocrystalline copper, as well as the highprobability for atoms to move across grains in nanocrystalline materials.