The investigation of conduction in anodic tantalum oxide films formed on sputtered tantalum

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Abstract
Current-voltage measurements have been carried out at room temperature on anodized tantalum thin films ranging in thickness from 120 to 400 nm. The tantalum was prepared by getter sputtering in such a way as to reduce the possibility of impurities and defects being present as was found in tantalum foil. The films were found to be rectifying, the forward direction of current flow being with the aluminium counter-electrode positive with respect to the base tantalum. The conduction mechanism is believed to be space-charge-limited in the forward direction and Schottky-controlled emission in the reverse direction. The current in the forward direction was on average two orders of magnitude higher than that in the reverse direction, and the mobility of the electrons in the space-charge-limited mode, as obtained from steady-state and transient measurements, is very low, being of the order of 10−17 m2 V−1 s−1. The results in general support those of Aris and Lewis (1973) and show that localized conduction does not play an important part in the conduction process.