Study of Titanium Oxide Nanoporous and Nanotubular Layer Formation Using Electrochemical Impedance Spectroscopy

Abstract

Nanoporous and nanotubular titanium oxide layers were fabricated by electrochemical etching in a mixed organic–inorganic electrolyte. The process of layers formation was investigated in−situ using the electrochemical impedance spectroscopy method. The experimental data show that, except for an initial stage of electrolytic etching, the impedance of a porous titanium oxide layer during almost the entire process is determined by the impedance of a small contact area of electrolyte/titanium oxide at the bottom of the nanoporous and nanotubular layers. The observed higher resistances of space charge region in the titanium oxide layer in comparison with the resistance of charge transfer at the electrolyte/TiOx boundary testify that the growth rate of porous and nanotubular layers is limited by the diffusion of titanium and oxygen ions through the oxide layer, and not by the diffusion of ions in the electrolyte.