pits is favoured. Therefore, in these zones the effect of the field enhanced
oxide dissolution is much larger than that occurring among
the pits and also in non-imprinted region (see Fig. 4). Taking into
account that the oxidation take place at the same time along all
the metal/oxide interface, the lateral oxide on the walls of the pits
has to grow vertically which could be considered as the origin of
the pores [29], Furthermore, the two different heights observed
in the AFM images can be explained considering the aluminium
volume expansion during oxidation. In this work, we have used
the optimal experimental conditions to obtain self-organized
growth of pore arrays when oxalic acid solution is used as electrolyte.
On non-indented zones the anodic oxide grows like ordinary
protective passive alumina films. On the contrary, on nanoindented
zones the anodic oxide growth mechanism is regulated by
mechanical stress mentioned before provoking an oxide growth
rate much higher. The alumina layers grown in nanoindented regions
are about 10 nm thicker than that grown on areas that have
been only electropolished.