Uniform and reproducible barrier layer removal of porous anodic alumina membrane.

A method for the fabrication of porous anodic alumina (PAA) membrane without bottom barrier layer on Al substrate is described. In this method, two-step anodizing followed by a barrier thinning process at the end of the second anodization was used to prepare wide range highly-ordered PAA membrane with a thin barrier layer. Finally, cathodic polarization and pore widening processes were combined to remove the barrier layer completely between the oxide film and Al substrate. Scanning electron microscope (SEM) was used to characterize the morphology and structure of the PAA membrane. From the SEM images, the PAA membrane prepared with the assistance of cathodic polarization showed more homogeneous pore diameters and pore wall quality than that made by pore widening only. In addition, the barrier layer was removed completely with 7.5 min of cathodic polarization and 70 min of pore widening without corrosion in the Al substrate. It was possible to control the pore diameter without any damage to the PAA template from 70 to 90 nm. The fabricated PAA template can be applied to the growth of ordered nanowires, nanorods, nanotubes, and similar structures.