Abstract
A self‐consistent development is given of a model of oxidation kinetics in which growth rate is determined by thermionic emission of electrons over a potential barrier due to the metal‐oxide work‐function and modified by space charge due to trapped electrons in the oxide and compensating surface charge at the metal‐oxide interface. The following expression is derived for the growth rate
where 
is the oxide film thickness at time 
, and 
is the characteristic thickness at which a uniform concentration 
of trapped electrons of charge 
attenuates the growth rate significantly at temperature 
, ε is the relative dielectric constant of the oxide, and 
is the Boltzmann constant. The parameter 
can be considered to determine the time scale, where 
is the flux of electrons (or charge) in the parent metal which impinges on the potential barrier of height φ represented by the oxide, and β is the volume of oxide formed per electron (or per unit of charge) which traverses the oxide film. This growth‐rate expression clearly does not lead to a direct‐logarithmic growth law. Moreover, the characteristic film thickness 
at which rate is significantly attenuated is of the order of the Debye length, in contrast with the conclusion reached by Nwoko and Uhlig that space‐charge effects should be much larger. A development of the activation barrier for electron emission illustrates that the electron affinity of adsorbed oxygen is not a factor in the activation energy for electron emission when the emission process is rate‐limiting. This results in a modification of the time scale for the kinetics by many orders of magnitude relative to that of Uhlig and Nwoko. Finally, the nonzero ionic current will perturb the rate‐limiting electron current; the "coupled currents" method previously developed by the present author, in which the currents are balanced by the surface charge field, is suggested to be appropriate for studying this effect.