ELECTRONIC STRUCTURE OF IRIDIUM OXIDE-FILMS FORMED IN NEUTRAL PHOSPHATE BUFFER SOLUTION

Iridium oxide films were formed by potential cycling in neutral phosph ate buffer solution (pH = 6.9) and studied by capacitance and photoele ctrochemical measurements, and by TEM. The results have revealed p-typ e semiconductivity of the oxide. The increase of the electric conducti vity occurring simultaneously with the colouring of the film is explai ned by a transition, at the film\electrolyte interface, from a Schottk y barrier to an ohmic contact. This transition takes place at the flat band potential; which is close to the potential of the main voltammetr ic peak. The doping values obtained from the Mott-Schottky approach ar e related with the porous structure of the film. (C) 1998 Elsevier Sci ence S.A.