Abstract: The semiconducting properties of the oxide film formed on chromium were studied by capacitance measurement and the Mott-Schottky analysis. It is shown that the oxide films formed on chromium within the passive potential region in 0.5 mol•L－1 H2SO4 solution, the thickness of which is about 1.2±0.3 nm, behavior like a p-type semiconductor. The impedance response of the film showed a low-frequency dispersion, which can be accounted for by dielectric relaxation with complex capacitance. The effects of the film-formation potential, the polarization time, and the solution pH on the semiconductive parameters of acceptor density (NA) and flatband potential (EFB) were investigated. The increase of NA corresponds to the increase of the hydration degree of the oxide films. The linear relationship with a slope of ～59 mV/pH unit between EFB and solution pH was observed.

Key words: Chromium, Passive film, Capacitance measurement, Acceptor density, 　Flatband potential