A combined process of electropolishing, focused-ion-beam lithography, and controlled anodization is used to fabricate anodic alumina films with ordered nanochannels. The ion beam is used to create a hexagonally close-packed lattice of concaves on a polished aluminum surface and the concaves act as pinning points for guiding the growth of nanochannels in the following anodization step. By carefully matching the lattice constant (100 nm) with the anodization voltage, ordered nanochannels with aspect ratio of ∼100 are fabricated. The effects of the ion dose and its corresponding depth of the concaves on the ordering of the nanochannel array are investigated and a minimum depth of 3 nm is found to be necessary for effective guidance of the growth of ordered nanochannels.

Arrays of ideally ordered alumina nanochannels with unprecedented ∼10nm pore size, 40–50 nm interpore spacing, and improved channel uniformity have been fabricated by anodizing an aluminum substrate with a guiding pattern on its surface. The pattern is an array of hexagonally close-packed concaves fabricated by focused ion beam direct sputtering; and its lattice constant is carefully matched to the conditions of the subsequent anodization process in order to achieve effective guiding in the growth of the nanochannels and therefore the ordering of an array.