The effect of anodizing voltage on the electrical properties of Al–Ti composite oxide film on aluminum

The Al–Ti composite oxide film with high dielectric constant was prepared by hydrolysis precipitation and anodizing. The depth profiles of the Al–Ti composite oxide films formed at 50 V and 80 V have been detected by glow discharge optical emission spectrometry (GDOES). The electrical properties of the Al–Ti composite oxide film formed at different anodizing voltages have been studied by electrical measurements. The local electric breakdown occurs in the Al–Ti composite oxide films about the anodizing voltage of 70 V. The Al–Ti composite oxide film formed at 80 V presents a thicker outer layer containing titanium than that of the film formed at 50 V. It was established that the dependence of the retention voltage and reciprocal capacitance on the anodizing voltage consisted of two linear regions. It was found that more than one conduction mechanism was involved in the range of electric field used in the experiment. The current conduction is ohmic at low electric field and Schottky emission at high electric field. The film formed at 80 V reveals an additional electric field region when compared with the film formed at 50 V, and its conduction mechanism is space charge limited current. According to our results, the film formed above the anodizing voltage of 70 V exhibits inferior electrical properties than that of the film formed below 70 V.