An apparatus for ion-beam-sputtering is described which offers for the first time the possibility of measuring radiotracer diffusion profiles with mean diffusion length (Dt) 1/2 (D is the tracer diffusion coefficient and t is the diffusion time) in the nano-as well as in the micrometre range. It is also possible to use the device for ion milling, especially for the deposition of thin layers of radiotracer onto diffusion samples. Investigations of diffusion in pure metals, in a metallic glass, in a compound semiconductor and in intermetallic compounds are presented as examples.
ChemInform Abstract As result of diffusion studies of Co in Nb between 1422 and 1561 K, using the radiotracer method combined with serial sectioning, two-stage penetration profiles are observed in agreement with predictions from the dissociative model (interstitial(Coi)-substitutional(Cos) diffusion via vacancies (V): Coi + V Cos). This mechanism predicts vacancy-limited diffusion in the near surface region where the surface represents the main source of vacancies and Coi-limited diffusion at greater depths where dislocations warrant virtually instantaneous vacancy supply.
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