Formation of thick porous anodic alumina films and nanowire arrays on silicon wafers and glass

A method for the fabrication of thick films of porous anodic alumina on rigid substrates is described. The anodic of the barrier layer between the porous film and the substrate was different from that of anodic films grown on aluminum substrates. The removal of the barrier layer and the electrochemical growth of nanowires within the ordered pores were accomplished without the need to remove the anodic film from the substrate. We fabricated porous anodic alumina samples over large areas (up to 70 cm(2)), and deposited in them nanowire arrays of various materials. Long nanowires were obtained with lengths of at least 9 mum and aspect ratios as high as 300. Due to their mechanical robustness and the built-in contact between the conducting substrate and the nanowires, the structures were useful for electrical transport measurements on the arrays. The method was also demonstrated on patterned and non-planar substrates, further expanding the range of applications of these porous alumina and nanowire assemblies.