The growth and properties of thin oxide layers on tantalum electrodes

Dedicated to the memory of Prof. Dr. Dr. h. c. Kurt Schwabe.
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Abstract

The dependence of the growth of thin oxide films on tantalum electrodes on the electrode potential (0V<E<10V) and pH (0<14) was investigated by coulometric and simultaneous impedance measurements. After chemical polishing, there is a thin film of about 2 nm thickness. At anodic polarization, the film grows by 1.76 nm/V. The dielectric constant D is about 25. Various anions (NO3, ClO4 and SO2−4) have no influence, but the pH shifts the oxide growth by −60mV per pH unit. Thin films behave as n-type semiconductors, and show a Schottky-Mott behaviour at negative potentials E<0 V. The donor density decreases with increasing thickness so that films thicker than 10 nm behave as pure insulators. Cathodic hydrogen evolution takes place at large overvoltages of about −1V. The characteristic potentials of passive tantalum are compared and discussed. All potentials show a shift of 60 mV per pH unit, which is typical for the adsorption equilibrium of hydroxide ions from the electrolyte. The flat band potential and the potential of the beginning of oxide growth are very close to the thermodynamic equilibrium potential of tantalum oxide. Using these results, we give a tentative energy diagram of the passive film.

References (30)

  • D. Galizzioli et al.

    J. Electroanal. Chem.

    (1973)
  • M.A. Habib et al.

    Electrochim. Acta

    (1982)
  • R. DeGryse et al.

    J. Electrochem. Soc.

    (1975)
  • M.A. Butler et al.

    J. Electrochem. Soc.

    (1978)
  • K. Schwabe et al.
  • K. Schwabe et al.

    Z. Phys. Chem. NF

    (1975)
  • L. Young
    (1961)
  • H.V.K. Udupa et al.
  • J.F. Dewald

    J. Electrochem. Soc.

    (1955)
  • J.P.S. Pringle

    J. Electrochem. Soc.

    (1973)
  • D.A. Vermilyea

    J. Appl. Phys.

    (1961)
  • P. Clechet et al.

    C.R. Acad. Sci.

    (1976)
  • H. Bispinck et al.

    J. Appl. Phys.

    (1979)
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    On leave of absence from Univers. Nacional de Cordoba, Fac. Ciencias Quimicas, Cordoba, Argentina.

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