The kinetics of surface segregation in thin films: theoretical considerations and the determination of diffusion data

Abstract

The kinetics of surface segregation out of thin films with low bulk concentrations is discussed assuming that the surface saturation is determined not by the usual McLean model but by the limited supply from the bulk, i.e. bulk depletion. It differs from the behavior of an infinite sample with an unlimited supply quite distinctly as soon as Einstein's diffusion length equals the thickness of the sample. Since surface segregation is frequently used to evaluate diffusion data from measured enrichment curves formulae appropriate for this special case are given. The linear temperature ramp again turns out to be a very valuable and powerful tool, although not quite as simple in its use as in the case of an unlimited supply.