Influence of Space Charge During the Oxidation of Metal Surfaces

Abstract

In this work we present a model for the surface oxide film growth considering the influence of space charge. The space charge field Esp is assumed proportional to the charge of moving metal ions and electrons in the oxide layer. The surface charge field Eox decreases as the Cabrera and Motts’ oxide thickness X grows to its limit X1 (Eox = VM/X). Eox remains constant for further growth of the oxide film (Eox = VM/X1). The obtained equation for the growing rate of the oxide film covers two stages. The first stage is characterized by a negligible space charge and is described by the typical inverse logarithmic law. During transition from thin to thick film, the oxidation growth rate is described by a direct logarithmic law which is confirmed by many experiments. At the end of this stage, the drift of metal ions is replaced by their diffusion that leads to parabolic law.