The influence of the alumina barrier-layer thickness on the subsequent AC growth of copper nanowires

In order to reveal the role of the alumina barrier-layer thickness, delta(b), On the copper nanowires electrochemical growth within the alumina pores, the experiments varying porous alumina template parameters and subsequent AC electrolysis conditions were performed. A linear dependence of delta(b) on the final anodizing voltage, was verified from 40 to 5 V by the electrochemical impedance spectroscopy technique. The further decrease in U-a,U-fin was not followed by the concomitant decrease in delta(b) presumably due to uneven formation of the native aluminum oxide in a reaction between the aluminum and ambient oxygen. The spectrometric analysis of deposited copper content has shown that the range of AC voltages used for copper nanowires growth within the alumina pores sharply increases with decrease in the U-a,U-fin and so, in the delta(b). The most favourable U-a,U-fin range for the uniform growth of' copper nanowires is 15-7.0 V. This is because: (i) the decrease in U-a,U-fin below 7 V results in the alumina framework peeling off from the Al surface, during subsequent AC electrolysis; (ii) the AC filling of template with delta(b) > 20 nm (U-a,U-fin > 20 V) leads to the breakdown of alumina. (C) 2004 Elsevier B.V. All rights reserved.