Micro-EIS of anodic thin oxide films on titanium for capacitor applications

The present work focuses on the investigation of the effect of the different crystallographic orientation of titanium grains on the formation of anodic oxide films and consequently their dielectric and semiconductive properties. By using a microcapillary cell the formation process and the electrochemical impedance spectroscopy (EIS) can be performed at high lateral resolution on variously orientated single grains of polycrystalline titanium. The oxide films were potentiodynamically formed by cyclovoltammetry. EIS measurements immediately followed by the oxide formation were used for a detailed investigation of the film properties, in particular, the relative permittivity epsilon(r) and the donor concentration N-D. In contrast to the most publications it was found that under the chosen conditions the crystallographic orientation of titanium substrate has no significant influence on the oxide thickness d, the relative permittivity epsilon(r). or on the donor concentration N-D of the oxide films. The relative permittivity epsilon(r) is approximately 50. The donor concentration depends on the film thickness and amounts to approximately 3 x 10(18) cm(-3) in minimum.