Scaling of Roughness in Silver Electrodeposition

The electrodeposition of silver from thiosulfate solutions and its surface roughness are studied using scaling methods. Although silver electrodeposition from photographic fixing baths containing thiosulfate has been done successfully for many years, the vast majority of information about this process remains empirical. A comparison is made between plating silver from ammonium- and sodium-thiosulfate-containing solutions. Atomic force microscopy is used to study surface roughness, which is then analyzed by scaling methods. Silver electrodeposition from sodium-thiosulfate-containing solutions was found to be smoother than from ammonium-thiosulfate-containing solutions. The obtained scaling exponents, found after correction for local effects, depend strongly on the nature of the electrolyte; the growth exponents β are 0.13 and 0.71 for sodium and ammonium thiosulfate solutions, respectively. Local effects are observed only for the sodium but not for the ammonium thiosulfate solution.