Cabrera-Mott interface

Growth of surface oxide films takes place only if cations, anions, and electrons can diffuse through the oxide layer. The growth kinetics of very thin films ( 10-50 A) often follow the Mott or Cabrera-Mott mechanisms in which electrons tunnel through the film and associate with oxygen atoms to produce oxide ions at the surface. A large local electric field (10 -10 V/cm) results at the surface which facilitates cation diffusion from the metal-oxide interface to an interstitial site of the oxide. The film thickness Z at time t is given by... 

Numerous other models have been proposed to explain the deviation of dry oxidation from linear-parabolic kinetics. For example, field-assisted oxidant diffiision during the oxidation of metals was proposed by Cabrera and Mott (75) and used by Deal and Grove (69) to explain the results for thin oxides. Ghez and van der Meulen (76) proposed the dissociation of molecular oxygen into atomic oxygen at the Si-Si02 interface and the re-... 

This model locates the rate-determining step within the oxide however, it can also be located at the interfaces without differences in the mathematical description [iii]. Refs. [i] Pringle JPS (1980) Electrochim Acta 25 1423 [ii] VerweyEJW (1935) Physica 2 1059 Lohrengel MM (1993) Mater Sci Eng R11-.243 [iii] Cabrera N, Mott NF (1948-49) Rep Prog Phys 12 163... 

If it is assumed that regeneration does not disturb the oxide already present on the surface, then further oxidation should be governed by the transference of cobalt cations from the metal-oxide interface to the oxide-gas interface where reaction takes place. The rate would be dependent on the total film thickness if the theory of Mott and Cabrera were valid. The limiting thickness then would be the sum of the defined limiting thickness Xl for a particular oxidation plus the thickness of the oxide layers previously formed. These total limiting thicknesses for successive oxidations, desig-... 

In contrast, Mott [75,76] and Cabrera [15, 48] considered the ITR of metal ions at the interface M/ox, that is. Reaction (15) as rate determining step. Since both models yield the same Eq. (31), a decision is still open. 

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