SELF-AFFINE FRACTAL ELECTRODEPOSITED GOLD SURFACES - CHARACTERIZATION BY SCANNING-TUNNELING-MICROSCOPY

The morphological evolution of columnar gold electrodeposits grown at 100 nm s-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 (zeta) depends on the scan length (L) as zeta is-proportional-to L(alpha) with alpha = 0.49 +/- 0.07 for L > d(s), where d(s) is the average top columnar size, and alpha = 0.90 +/- 0.07 for L < d(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.