Anodic oxides were grown to 50 V on Ta in several organic ions containing anodizing baths. Their properties were compared with anodic Ta oxide film grown to the same formation voltage in 0.1 M NaOH. Anodizing process carried out in sodium citrate led to the growth of the anodic oxide with the best blocking properties whilst, when Ta is anodized in sodium adipate, a significant part of the circulated charge is wasted in side reactions, such as oxygen evolution. Photoelectrochemical measurements showed the presence of optical transitions at energy lower than the band gap for the anodic films grown in citrate and tartrate electrolytes, attributed to localized electronic states located close to the valence band mobility edge of the films generated by anions incorporation into the oxide. Differential capacitance measurements proved an increase by 17% in capacitance value for the oxide grown in citrate-containing solution with respect to that grown in NaOH electrolyte. A sketch of the energetic of the metal/oxide interface is provided.

Graphical abstract

阳极氧化物在几种包含阳极浴的有机离子中在Ta上生长至50V。将其性能与在0.1 M NaOH中生长到相同形成电压的阳极Ta氧化物膜进行了比较。在柠檬酸钠中进行的阳极氧化工艺导致具有最佳阻断性能的阳极氧化物的生长，而当在己二酸钠中对Ta进行阳极氧化时，很大一部分循环电荷被浪费在副反应中，例如放出氧气。光电化学测量表明，在低于柠檬酸盐和酒石酸盐电解质中生长的阳极膜的带隙处，存在能量处的光跃迁，这归因于局部电子态，该电子态位于靠近阴离子结合到氧化物中而产生的膜的价带迁移率边缘。差分电容测量证明，与在NaOH电解液中生长的氧化物相比，在含柠檬酸盐的溶液中生长的氧化物的电容值增加了17％。提供了金属/氧化物界面的能量的草图。

图形概要