Effect of Electric Field Strength on Cell Morphology and Anion Incorporation of Anodic Porous Alumina

The effect of electric field strength (E) on cell morphology and anion incorporation of porous anodic alumina films was studied by using TEM. Cell diameter decreased with decreasing voltage until 2V while pore diameter decreased to a minimum at 5V, followed by an increase at 2V. The ratio of cell diameter to pore diameter (d(cell) / d(pore)) of the anodic films formed in sulfuric acid and oxalic acid solutions at different constant voltage was in a linear relationship with logarithm of current density (log i). Since E across the barrier layer of porous films varied linearly with log i as in the case of barrier type film, the d(cell) / d(pore) ratio was regarded to be proportional to E. From the obtained results, it is deduced that pore diameter is proportional to voltage and inversely proportional to the square of E, whereas barrier layer thickness and cell diameter are proportional to voltage and inversely proportional to E. Accordingly, pore diameter is more dependent on current density than the other cell parameters are. The content of incorporated anion in the films increased linearly with increasing log i, hence E.