Measurement of defect-mediated diffusion: The case of silicon self-diffusion

In many solids, diffusion of foreign atoms takes place primarily through highly mobile intermediate species that periodically exchange with atoms in the crystalline lattice. A method is developed for determining key diffusion parameters via the short-time decay of an initial step concentration profile. This method takes advantage of the relative ease with which step concentration profiles can be fabricated by thin film deposition, and in the limit of very short times provides particularly simple analytical means for obtaining parameters connected to diffusion length and defect formation. Application of the method to isotopic heterostructures of silicon shows that under the ultrahigh vacuum conditions of the experiment, interstitial atoms mediate self-diffusion.