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

The oxide films formed on AISI 304L stainless steel at 300 degrees C in the oxidation time range between 2 and 4 h 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 serniconductive 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 = 2.16-2.3 eV) depending on the applied potential and oxidation time, higher to that of the external oxide layer (E-G1 approximate to 1.9 eV). Significant variations in the amplitude of the photocurrent were detected as a function of the applied potential and the oxidation time. (c) 2005 Elsevier B.V. All rights reserved.