Di-block copolymer directed anodization of hexagonally ordered nanoporous aluminum oxide

Porous anodized aluminum oxide (AAO) nanostructures have been extensively investigated as versatile templates for nanodots and nanowires for many applications. Such self-ordered AAO structures are often achieved by so-called two-step anodization. Ordered pore arrangements can be obtained in the second step after removing the AAO layer formed in the first anodizing step, during which hexagonally ordered, concave-pored Al surface is formed so as to serve as vertical pore nucleation sites for the subsequent anodization step. Although such a two-step anodization process has proven useful for bulk Al surface, the relatively large amount of Al material that needs to be used up to obtain a well ordered AAO template is an issue when the starting material is a thin film layer of Al rather than a bulk Al foil. In this paper, we demonstrate successful fabrications of ordered and vertically aligned AAO nanopore patterns directed by a hexagonally patterned poly(styrene-b-4-vinylpyridine) di-block copolymer layer placed on a thin Al film surface. In addition, a successful electrodeposition of Ni nanowires into the AAO nanopores is demonstrated and their magnetization properties are studied.