Influence of oxidation time on semiconductive behaviour of thermally grown oxide films on AISI 304L

Abstract: The oxide films formed on AISI 304L stainless steel at 300°C in the oxidation time range between 2 and 4h have been studied by photoelectrochemistry. Photocurrents were investigated as a function of the wavelength of the incident light and the electrode potential. The investigation allowed the determination of the semiconductive properties of the oxides. The oxide films showed n-type behaviour. A duplex structure of the oxide films has been suggested on the basis of the photocurrent spectra, with an internal oxide layer having an optical gap (E g2 =2.16–2.3eV) depending on the applied potential and oxidation time, higher to that of the external oxide layer (E g1 ≈1.9eV). Significant variations in the amplitude of the photocurrent were detected as a function of the applied potential and the oxidation time. [Copyright &y& Elsevier]