In situ monitoring of intrinsic stress changes during copper electrodeposition on Au(111)

Abstract

In this paper we report on the stress evolution during multilayer copper electrodeposition on Au(111). In particular, we investigated the dependence of the stress on the overpotential and made use of the knowledge established in surface science to identify the structure of the resulting films. We have adapted the method of monitoring the bending of a cantilever sample by STM to measure stress changes during the bulk electrodeposition. We find that the bulk copper films develop tensile stress, in contrast to the compressive stress resulting from the formation of the first monolayer at underpotential. The tensile stress changes for the bulk film, for an equivalent film thickness, increase with increasing overpotential. We relate these stress changes to (small angle) grain boundaries between adjoining copper growth centres. A larger grain boundary contact area results from the finer-grained deposits formed at higher overpotential. For equivalent deposition overpotential, copper electrodeposition, in both the absence and presence of crystal violet, gives rises to comparable stress evolution, resulting from the common source of the intrinsic stress.