Anomalous Diffusion in Non-Metals (Origin and Effects of Internal Electric Fields),

摘要

When electrically active impurities or defects diffuse in a material with a band gap > 10 kT,the changing concentration of these ions may result in internal electric fields which will significantly alter the diffusion process,and result in gross misinterpretation of diffusion experiments. Equations are derived which describe the diffusion of interstitial impurities in such a system,and which take proper account of compensating immobile impurities. A technique for numerical solution of these equations is described and the results of calculations for the case of H(+) in TiO2are presented. These calculations predict a large enhancement of the overall diffusion rate and a very distinctive concentration profile. Experimental results for the H(+)-TiO2system are presented,which agree quantitatively with calculations. (Modified author abstract)