Photoconductivity in anodic Ta2O5formed on nitrogenhyphen;doped tantalum films

摘要

Photocurrent spectroscopy (or the spectral response of photoconductivity) and transient photoconductivity have been used to probe the defect structure (trap states) of anodic Ta2O5films formed on pure and nitrogenhyphen;doped sputterhyphen;deposited tantalum. Results of this investigation indicate the presence of two traphyphen;related responses at 1.5 and 2.8 eV, respectively. Nitrogen in the oxide is found to compensate these traps, that is, the amplitude of the photocurrent response is observed to decrease with increasing nitrogen concentration. The recombinationlike trap at 2.1 eV, present in pure Ta2O5, is not observed in samples doped with as little as 2 at.percnt; N2. Transient results indicate a spatial localization of the 1.5hyphen;eV trap which may be related to the nonuniform nitrogen distribution in the oxide. Nitrogen in the oxide was found to have little effect on the bandhyphen;gap energy (4.4 eV).