Study On Preparing Metal And Metal Alloy Nanowires & Nanotubes Using AAO Template

Molecular sieves, track-etched polymer membranes and porous anodic alumina are representative templates. Porous anodic alumina are considered as particularly attractive template materials for fabricating nanowires, because it possesses some special characters including uniform highly oriented, nearly parallel pore and small diameter. Porous alumina, fabricated by anodization of aluminium in oxalic acid, sulfuric acid, phosphate acid, contains cylindrical pores whose diameters range from 10nm to 200nm, depending on the anodization conditions. At the oxide/metal interface there is a layer named barrier layer, whose thickness remains constant during the course of oxidation and is proportional to the voltage. There is an insulative and rather thick barrier layer (1-1.2 nm per volt oxidation pot) at the interface between the alumina layer and the metallic aluminium substrate, which resists the cathodic current. In order to obtain a good electrical contact at the pore bottom, the high cathodic current is needed to deposit metal, but the over high cathodic current causes some hydrogen evolution, which may inhibit the process of deposition. Therefore, both the aluminum plate and the barrier layer should be removed by a chemical etching method using appropriate solution. Then, a conductive (Au, Ag, Cu) film is sputter-deposited on one side of the membrane to serve as the working electrode in order to fabricate nanowires by the method of...