Atomic force microscope (AFM) was utilized to investigate the unstable growth of porous anodic aluminum oxide (AAO) membrane. The results showed that the unstable growth of AAO membrane resulted in the decrease of the order degree of its special nano-channels. The AAO membrane growing in H₃PO₄ solution is unstable, while the growth stability in H₂C₂O₄ solution will depend on its anodized voltage and current density: stable in low voltage and low current density while unstable in high voltage and high current density. By controlling the condition of the anodized process, the special AAO template with branched channel structures can be formed because of the unstable growth of the membrane. This may provide a new opportunity for fabricating Y-shape or T-shape nanowires and nanotubes by using the template method.

Key words: atomic force microscope, anodic aluminum oxide, unstable growth, branched structure