Concentration effect of the solutions for alumina template ac filling by metal arrays

The influence of the cMez+ in acidic solutions of Cu, Ni, Co, and Sn salts on the amount of deposited metal, mMe, by ac electrolysis in the pores of various alumina templates grown in commonly used aluminium anodizing solutions of sulfuric, oxalic, phosphoric and chromo-boric acids was investigated. Behaviour of the porous alumina under ac voltage control manifests itself through mMe–cMez+ parabola dependencies. The peaks of mMe–cMez+ plots was found to be dependent on the alumina pore diameter, dp, and composition of the metal salt solution used. An increase in dp and decrease in a solution pH shifts mMe versus cMez+ dependencies and the optimal cMez+ toward smaller solution concentrations. From the results of the voltammetric and chronopotentiometric studies a surprisingly large value of a few seconds of the transition time for hydrogen ions discharge, occurring before the metal ion reduction at the bottom of alumina pores, was obtained. This result makes it reasonable to suggest that the amount of Me(OH)x, formed in the pore base region due to the hydrogen evolution from the acidic solutions with bulk concentration 0.1–0.2 M, is the most favourable to the deposition of metal arrays at the highest rate if 13.5≤dp≤37.5 nm.