Direct Fabrication of High-Aspect Ratio Anodic Aluminum Oxide with Continuous Pores on Conductive Glass

The role of metal interlayers in maintaining adhesion during the direct fabrication of anodic aluminum oxide (AAO) with high-aspect ratio pores on tin-doped indium oxide (ITO) is studied. Chromium and titanium interlayers can maintain adhesion while anodization is conducted in either sulfuric, oxalic, or phosphoric acid solutions. However, the ability to form high-aspect ratio pores is dependent on the interlayer and aluminum thickness, the method of aluminum deposition, and possibly the cleaning/surface treatment of ITO prior to aluminum deposition. AAO films approximately 2 mu m thick were prepared in oxalic and phosphoric acids, yielding high-aspect ratio pores with length to diameter ratios of 47 and 14, respectively. The distinct stages of pore formation are also correlated with the time-resolved current response of the anodization cell, which provides in situ information about the anodization process so that adhesion can be maintained throughout pore formation. The direct fabrication of AAO on ITO/glass substrates from a single-step evaporation of thick aluminum films enables the formation of smooth and continuous gold nanowires, which have potential applications in photonics. (c) 2010 The Electrochemical Society. [DOI: 10.1149/1.3506007] All rights reserved.