Electrochemical Impedance Spectroscopy Study of Porous Anodic Alumina Films Fabricated at Low Temperature

Abstract

A method of fabrication of AAO film in 0.3 mol/L H₂C₂O₄ by adding 1,2-propanediol(PROH) and at sub-zero temperature has been proposed. The electrochemical characteristics of the barrier and porous layers of AAO films before and after pore-filling are examined using electrochemical impedance spectroscopy (EIS). It is shown that the high and medium frequency range corresponds to the barrier layer properties and the low frequency ranges reflect the sealed porous layer properties. The calculated thickness of the barrier layer is in the range of 1 ~ 18 nm. The resistance (R_b) and the thickness (δ_b) of the barrier layer increase and the capacitance of the barrier layer (CPE_b) decrease with the volume percentage of PROH increasing from in electrolyte from 25 % to 75 %. The surface non-homogeneity of AAO film goes better by pore-filling, leading to a decrease in the capacitance of the porous layer (CPE_p) and an increase in the porous layer thickness.