Anodic oxide films on titanium formed in molten salt electrolytes—I. Estimation of p-i-n junction in the film☆

Abstract Titanium was oxidized anodically in molten sodium nitrite, and sodium nitrite containing 1 mol-% sodium peroxide, at constant cd at 315°C. The anodic oxide film showed rectification, and photocurrent and photovoltage. From these results and the measurements of capacitance of the film, the film is proved to consist of a p-i-n junction. The n-region is in contact with titanium electrode and the p-region is in the outermost layer of the oxide. The i-region is between the n- and p-region. The profile of impurity distribution in the p- or n-region is divided into two parts, a graded and a constant distribution region. The parameters of the junction were calculated. The theory of “Zener breakdown” was adopted for the breakdown of the oxide film; the electric field at the breakdown voltage was about 10 6 V/cm.