Nanoporous templates, such as anodic porous alumina, have gained much importance in the last 20 years due to their potencial industrial and technological applications for nanometric device fabrication. In fact, because the existent nano-lithographic techniques (e-beam. X-ray, focused ion beam) are expensive and have a low throughput, new assembling methods are needed for the large scale inexpensive production of nanodevices. Nanoporous anodic alumina templates, which can be readily obtained by common electrochemical processes, may be one such method for achieving the required nanodimensions. These templates can be used to obtain different nanomaterials such as nanodots, nanochannels or nanowires, showing their versatility of use. Furthermore, the fact that different ordered structures (hexagonal, square or triangular lattices) have been obtained by two step anodization and pre-patterning techniques, opens new possibilities for the applications of nanoporous anodic alumina.

In this work we study how different pre-treatments (as-rolled, etanol degreasing, immersion in 1M NaOH for native oxide removal, diamond paste polishing, electropolishing and ion-milling etching) of high purity (99.997%) aluminum foils (prior to the first anodization step), influence pore growth and organization. Anodizations were carried out in 1.2 M H2SO4 for 1 hour, at room temperature. The current transients were monitored during anodization, allowing us to probe pore formation. After the first anodization we observed, using Scanning Electron Microscopy (SEM), the top of the anodized foil (alumina surface). The removal of this alumina layer allowed us to observe the pattern formed at the underlying aluminum surface. SEM images after the second anodization (under the same conditions as the first) were also performed. A comparative study of the influence in the porous structure of all pre-treatments will be shown and discussed.

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