Direct Evidence for Effects of Grain Structure on Reversible Compressive Deposition Stresses in Polycrystalline Gold Films

Abstract

A component of the compressive stress that develops during deposition of polycrystalline thin films reversibly changes during interruptions of growth. The mechanism responsible for this phenomenon has been the subject of much recent speculation and experimental work. In this Letter, we have varied the in-plane grain size of columnar polycrystalline gold films with a fixed thickness, by varying their thermal history. Without a vacuum break, the stress in these films was then measured in situ during growth and during interruptions in growth. Homoepitaxial gold films were similarly characterized as part of this study. The inverse of the in-plane grain size and the corresponding reversible stress change were found to be proportional, with zero reversible stress change observed for infinite grain size (homoepitaxial films). These results demonstrate a clear role of grain size in the reversible changes in gold films.