Titania Films Obtained by Powerful Pulsed Discharge Oxidation in Phosphoric Acid Electrolytes

Abstract

Thin TiO2 films were prepared on the titanium surface using the powerful pulsed discharge oxidation method (PPDO) in phosphoric acid based electrolytes. The obtained films were characterized with electrochemical impedance spectroscopy (EIS), photocurrent spectroscopy, scanning Kelvin probe force microscopy (SKPFM), and Mott-Schottky plot analysis. The potential dependence of the space charge layer capacitance has demonstrated that the ionized donor concentration in the oxide is strongly influenced by the electrolyte concentration used during the pulsed anodization. It is also shown that the main factor influencing the kinetics of the oxide film growth is the concentration of point defects which, in turn is determined by the composition of electrolyte. SKPFM results show a non-linear evolution of the Volta potential of the anodized surface with the film thickness reaching a plateau after film thickness exceeds 100 nm. The results obtained clarify the mechanisms of titania film formation under high-voltage pulses and allow tuning the semiconductive properties of thin oxide layers on titanium surfaces.