Preparation of highly ordered nanoporous Co membranes assembled by small quantum-sized Co particles

Highly ordered nanoporous Co membranes were fabricated by a two-step replic ation from the honeycomb structure of porous anodic alumina. These metal me mbranes are confirmed to have two substructures: first, the Co membrane con sists of very fine quantum-sized particles with diameters of about 2-5 nm; second, the very fine Co particles are assembled in a superstructure; i.e., fine and uniform channels 50 nm in diameter, more than 16 mm in thickness, having a pore density of about 10(10) cm(-2). New techniques were introduc ed into the two-step replication process. resulting in new features of the replicated metal membrane: high aspect ratio (more than 320:1), highly orde red pore arrays, and narrow size distributions of the pore diameters. These new techniques also lead to simplification of the fabrication process of m etal membranes. Double-sided and single-sided Co membranes can be achieved simply by adjusting the electroless deposition time. (C) 2001 American Vacu um Society.