Control of nano/microstructure and pit initiation sites on aluminium surface by use of self-assembled spheres

Nano/microstructure control and electrochemical etching of aluminium substrate using a honeycomb alumina mask fabricated by anodisation with self-assembled spheres aligned on the aluminium surface were studied to directly control the initiation sites of pits. The transfer of the hexagonally ordered pattern of self-assembled spheres to the aluminium substrate could be achieved by substantially suppressed anodic oxide growth under the spheres where selective electrochemical etching proceeded. That is, etch pits are generated only in the thinner areas or holes of the honeycomb alumina mask with a one-to-one correspondence. With this process, improvements in pit distribution density and the homogeneity of pit sizes, while avoiding excessive dissolution of the aluminium surface, could be achieved easily in comparison with the conventional method. The density of pits could also be controlled by changing the diameter of spheres used as an indirect mask. Copyright (C) 2010 John Wiley & Sons, Ltd.