Computer supported pulse measurements of current and capacity during fast oxide formation on iron

Computer supported potentiostatic pulse measurements are described which allow the determination of current density i in a wide range of / orders of magnitude of i and t. Pulse measurements of capacity in the same time scale reveal the electronic properties of the interface. Oxide film formation on iron is investigated as an example. Common models of high field mechanism of oxide growth and an n‐type semiconducting film are confirmed qualitatively, but in detail they have to be corrected. The n‐type semiconducting film represents only a part of the oxide, and the dielectric constant D and the donor concentration N decrease with time. The properties of a stable semiconductor develop slowly, parallel to the decrease of ionic currents in the film. That is also shown by the slow stabilization of the transpassivity.