Porous alumina membrane is prepared by aluminum anodizing in given acidic solution. Now
Porous alumina membrane is a type
of the famous template for fabricating nano-structural materials. The method of two-step anodic
oxidation improves the regularity of porous distribution greatly. For optimizing nano-structured assembling system, highly ordered porous alumina template is desirable. The cause of ordered
porous alumina membrane made by two-step anodic oxidation has been investigated. The regularity of holes arrangement in the membrane made by two-step anodic oxidation displayed better than that of the membrane anodizing only once from experimental results. The long-range ordered scope reaches 3～4 μm. However, the ordered scope of holes arrangement in two-step membrane is limited in several micrometers and difficult to improve. In order to raise the order degree, aluminum was annealed to increase the grain size. The result showed that annealing had no contribution to holes ordering. In fact, the sub-grain size of aluminum decides the dimension of ordered scope.