engleski

Conduction processes in the Ta(-)/Ta2O5-electrolyte system

Thin tantalum oxide (Ta2O5) films of controlled thickness d (from 1 to 80 nm) were obtained by the anodization of tantalum in a phosphate buffer at pH 7. Experimental results for the d.c. conduction characteristics of amorphous highly imperfect Ta2O5 films are presented. Semiquantitative agreement is observed between the experiment and theory. For electrodes covered with very thin films, direct electron exchange between the metal and the electrolyte predominates. In the high field region, for films thicker than 30 nm, the conduction mechanism is space charge limited. The effective electron mobility is 10-13 m2 V-1 s-1 for ε = 13. In the low field region, the data can best be interpreted in terms of an ohmic mechanism with a resistivity of approximately 5 × 1014 Ω cm. The band gap for these films was determined from the spectral distribution of the photoconductivity and amounts to 4 eV. The flat-band potential is approximately - 1 V vs. the Ag/AgCl electrode.

Ta2O5; phosphate buffer; semiconducting properties

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