Self-affine fractal electrodeposited gold surfaces: Characterization by scanning tunneling microscopy.

Abstract

The morphological evolution of columnar gold electrodeposits grown at 100 nm ${\mathrm{s}}^{\mathrm{\ensuremath{-}}1}$ by electroreducing a gold oxide layer on a gold cathode has been studied at a nanometer level by scanning tunneling microscopy. The interface thickness (\ensuremath{\xi}) depends on the scan length (L) as \ensuremath{\xi}\ensuremath{\propto}${\mathit{L}}^{\mathrm{\ensuremath{\alpha}}}$ with \ensuremath{\alpha}=0.49\ifmmode\pm\else\textpm\fi{}0.07 for Lg${\mathit{d}}_{\mathit{s}}$, where ${\mathit{d}}_{\mathit{s}}$ is the average top columnar size, and \ensuremath{\alpha}=0.90\ifmmode\pm\else\textpm\fi{}0.07 for L${\mathit{d}}_{\mathit{s}}$. These results prove that the growing surface can be described as a self-affine fractal for length scales greater than the columnar size. Conversely, the columnar surface approaches the behavior of an Euclidean surface.