Ion dynamics at porous alumina surfaces

Anodic porous alumina has broad applications for fabricating self-assembled nanostructures, for which atomistic understanding of ionic transport at pore surfaces is indispensable. Here, molecular-dynamics simulation of amorphous alumina with a cylindrical pore under electric field shows correlated anion (oxygen)-cation (aluminum) transport at the pore surface, as opposed to ordinary drift motion in the bulk. In particular, this phenomenon leads to inverted cation transport at the surface. Detailed analyses of simulation data reveal atomistic mechanisms of the correlated transport based on surface-structural relaxation and covalent oxygen-aluminum bond networks. These transport mechanisms have significant implications for alumina anodization processes. © 2012 American Institute of Physics.