Dynamic-scaling exponents and the roughening kinetics of gold electrodeposits.

Abstract

The kinetics of gold electrodeposit roughening was studied at the nanometer level by scanning tunneling microscopy (STM) and by using dynamic-scaling theory. Gold electrodeposits were grown at 100 nm ${\mathrm{s}}^{\mathrm{\ensuremath{-}}1}$ from the electroreduction of hydrous gold oxide layers. The following dynamic-scaling exponents were obtained: \ensuremath{\alpha}(I)=0.90\ifmmode\pm\else\textpm\fi{}0.06 and \ensuremath{\beta}(I)=0.31\ifmmode\pm\else\textpm\fi{}0.08 for ${\mathit{L}}_{\mathit{s}}$${\mathit{L}}_{\mathrm{sc}}$, and \ensuremath{\alpha}(II)=0.49\ifmmode\pm\else\textpm\fi{}0.05 and \ensuremath{\beta}(II)=0.51\ifmmode\pm\else\textpm\fi{}0.08 for ${\mathit{L}}_{\mathit{s}}$>${\mathit{L}}_{\mathrm{sc}}$, where ${\mathit{L}}_{\mathit{s}}$ is the scale length, and ${\mathit{L}}_{\mathrm{sc}}$ is a critical length closely related to the average grain size of the electrodeposit measured from STM imaging. Results from dynamic-scaling analysis are consistent with a grain surface smoothing mechanism involving surface diffusion of gold atoms.