Influence of magnesium and aluminium ions on the copper a.c. deposition into aluminium anodic oxide film nanotubes

Abstract

The influence of Mg2+ and Al3+ ions on a.c. deposition of copper nanowires into aluminium anodic oxide film (AOF) nanotubes has been studied using cyclic voltammetry and d.c. plasma emission spectrometry. From the analysis of copper quantities deposited into the Al AOF nanotubes (mCu), 0.02 M MgSO4 concentration was found to be optimal for Cu(II) solutions. Moreover, it was shown that Mg2+ and Al3+ ions not only prevent the breakdown of the barrier layer of AOF, but change the rate of copper deposition and modify the shape of the mCu against pH plots depending on the a.c. voltage applied. From the analysis of the quantities of magnesium (mMg) incorporated into the Al AOF nanotubes, presumably in the form of Mg(OH)2, the mMg against pH dependences were determined in MgSO4 and MgSO4 + CuSO4 solutions. An increase in mMg from 30 μg dm−2 to 1 mg dm−2 at pH 1.5 and from 6 μg dm−2 to 16 μg dm−2 at pH 7.0 was found under the same a.c. treatment conditions from MgSO4 solutions without and with Cu2+ ions, respectively, indicating the incorporation of Mg(OH)2 into the Al AOF nanotubes to be lower up to about one hundred times in the case of Cu deposition. Based on the experimental results, it was suggested that incorporation of the Mg(OH)2 particles into the Al AOF nanotubes occurred simultaneously with growing copper nanowires under a.c. bias is insignificant, if the pH of the CuSO4 + MgSO4 solution is ≤ 2.5.