CHEMICAL COMPOSITION AND ELECTRONIC STRUCTURE OF
THERMALLY GROWN OXIDE FILMS ON 304 STAINLESS STEEL
N. E. Hakiki*, B. Maachi
Laboratoire de Physique des Couches Minces et Matériaux pour l’Electronique
Faculté des Sciences, Université d’Oran Es-sénia, 31100 Oran Algérie
* Corresponding author. E-mail: firstname.lastname@example.org
Received: 06 February 2007; revised version accepted: 11 August 2007
The chemical composition and the electronic structure of thermally grown oxide films on stainless steel are investigated by Auger Electron Spectroscopy (AES), Near Field Microscopy (AFM), and electrochemical measurements (ac impedance and photoelectrochemistry). The analytical results show that the oxide films are in all cases composed by an inner region of a mixed chromium-iron oxide and an external region of iron oxide. The images obtained by AFM microscopy show the evolution of the well crystallization with the increasing of formation temperature. In other part, the raise in temperature of film formation does not affect the distribution of elements within the oxide. However, the thickness of the outer Fe2O3 layer changes markedly with the temperature of film formation. The ac impedance and photoelectrochemical results show that although very different in thickness, the oxide films present the same capacitance and photoresponse variations as the applied potential and the incident energy light revealing behaviour similar to that of semiconductor electrodes. However, the capacitance and the quantum efficiency values markedly decrease when the formation temperature increases.
Keywords: Oxide; Stainless steel; AFM; AES; Capacitance; Photocurrent.