Formation of dimpled tantalum surfaces from electropolishing

Electropolishing of tantalum in concentrated acids has recently been reported to result in highly ordered arrays of nanoscale dimples. In this paper we study in more detail the electrochemical conditions affecting the formation of regularly dimpled surfaces on tantalum. Solution aging and anodization potential were found to play important roles. The chronoamperometric curves at different anodization potentials give some insight into the changing balance of processes leading to dimpling during electropolishing. We have found that dimpled tantalum can be reproducibly prepared within the anodization potential range of 10-20 V. Higher voltages lead to anisotropic etching of the Ta grains and the resulting surface nanostructure is no longer ordered. Overall, the dimple-formation process can be said to be robust and tunable, with great promise for nanotemplating applications. (c) 2007 The Electrochemical Society.