Oct., 1963
COMPOSITION RANGEAND DECOMPOSITION PRESSURE OF NbsGe
and that the rate expression should be derived for constant field. When, for :L p-type oxide the growth rate in the very thin film region is controlled by the rate of formation of cation vacancies a t the oxide-oxygen interface, Grimley and Trapnell'O obtained a rate law which, provided the surface is heavily covered with adsorbed oxygen and neutral paire, predominate over field-creating ions, reduces without significant error to eq. 1. It is easily shown that for any reasonable value for the surface potential ( < 5 v.) the fraction of surface covered by field creating ions, e,, must be
