Enhanced Surface Layer Diffusion in Non-Metallic Compounds

摘要

The literature on the subject of enhanced surface layer diffusion in non-metallic compounds is critically reviewed. It is concluded that the enhancement results from an increase in the pre-exponential factor and that the diffusion mechanism is the same in both the bulk material and in the sub-surface layer. The space charge treatment of Lehovec is presented as the most fruitful source of a theoretical explanation, but it is also established that additional theoretical and experimental work must be undertaken to find the source of the observed increase in the pre-exponential factor of the diffusion coefficient. It is further concluded that, in general, dislocations do not contribte significantly to the enhanced diffusion in the sub-surface layer. Possible practical applications of the enhancement phenomenon are also presented. (Author)