Anomalous Scaling of the Surface Width during Cu Electrodeposition

Kinetic roughening during thin film growth is a widely studied phenomenon, with many systems found to follow simple scaling laws. We show that for Cu electrodeposition from additive-free acid sulphate electrolyte, an extra scaling exponent is required to characterize the time evolution of the local roughness. The surface width w\(l,t\) scales as t^β_locl^H, when the deposition time t is large or the size l of the region over which w is measured is small, and as t^β+β_loc when l is large or t is small. This is the first report of such anomalous scaling for an experimental ( 2+1)-dimensional system. When the deposition current density or Cu concentration is varied, only β_loc changes, while the other power law exponents H and β remain constant.