title: Fast fabrication of long-range ordered porous alumina membranes by hard anodization.
abstract: Nanoporous anodic aluminium oxide has been widely used for the development of various functional nanostructures. So far these self-organized pore structures could only be prepared within narrow processing conditions. Here we report a new oxalic-acid-based anodization process for long-range ordered alumina membranes. This process is a new generation of the so-called "hard anodization" approach that has been widely used in industry for high-speed fabrication of mechanically robust, very thick (>100 microm) and low-porosity alumina films since the 1960s. This hard anodization approach establishes a new self-ordering regime with interpore distances, (D(int))=200-300 nm, which have not been achieved by mild anodization processes so far. It offers substantial advantages over conventional anodization processes in terms of processing time, allowing 2,500-3,500% faster oxide growth with improved ordering of the nanopores. Perfectly ordered alumina membranes with high aspect ratios (>1,000) of uniform nanopores with periodically modulated diameters have been realized.
authors.affiliation: Max Planck Institute of Microstructure Physics, Weinberg 2, D-06120 Halle, Germany. woolee@mpi-halle.de
authors.forename: Woo
authors.initials: W
authors.lastname: Lee
authors.forename: Ran
authors.initials: R
authors.lastname: Ji
authors.forename: Ulrich
authors.initials: U
authors.lastname: Gösele
authors.forename: Kornelius
authors.initials: K
authors.lastname: Nielsch