On the mechanism of self-deceleration of the thin oxide film growth

The objective of this work was to investigate the kinetics of the two-phase oxide film growth on the alpha-Fe surface at temperatures of 650-750 K. We experimentally deter-mined that the film thickness (h)-time oxidation (tau) relationship in the range denoted above is a logarithmic function, whereas Cabrera and Mott's theory gives a square law of film growth. In our work. analytical treatment of experimental data was made based on this theory, but we propose that self-deceleration of the film growth is caused not by attenuation of the electric intensity in the film because of an increase of h but by the shielding influence of the space charge of diffusing ions and electrons in that oxide film. With that purpose in view, the Debye shielding distance for plasma substance state in the oxide film was taken into consideration. The logarithmic law of oxide film growth was derived. Estimated calculations of this law's parameters were made that quantitatively correspond with literature data. The results obtained were used in developing the surface oxidation technology of electric steel. (C) 2002 American Vacuum Society.