STM SEM AND IMPEDANCE CHARACTERIZATION OF COLUMNAR STRUCTURED GOLD ELECTRODES

The impedance spectra of thin gold electrodeposits with 10(-6)-10(-5) cm average columnar radius and 4 x 10(-6)-3 x 10(-4) cm average height have been measured in acid solutions. Frequency dispersion has been observed for film thicknesses greater than 3 x 10(-5) cm and electrolyte resistivities larger than 300-OMEGA cm-1. STM-SEM observations reveal a self-affine surface structure with a size distribution of pores ranging from 10(-6) to 10(-4) cm between the columnar elements. In diluted solutions the contribution of the smallest pores to the sampled electrode area decreases as omega increases explaining the observed frequency dispersion. This result confirms that self-affine surfaces exhibit a fractional-power-law impedance. However, no simple correlation was found between the alpha-value and the D-value of the self-affine surface measured by an independent method. The present results also show that the electrolyte resistivity plays a certain role in determining the alpha-value.