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 $t^{{\beta }_{\mathrm{loc}}}{l}^H$, when the deposition time $t$ is large or the size $l$ of the region over which $w$ is measured is small, and as $t^{\beta +{\beta }_{\mathrm{loc}}}$ 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 ${\beta }_{\mathrm{loc}}$ changes, while the other power law exponents $H$ and $\beta$ remain constant.

• Received 21 June 2000

DOI:https://doi.org/10.1103/PhysRevLett.86.256