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.

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Results on the temperature and pressure dependence of Ge diffusion in pure aluminium are reported. Radiotracer methods in combination with serial sectioning by microtome are employed in our experiments. Oxide hold‐up effects are avoided either by ion implantation of 71Ge or by sputtercleaning of the aluminium samples prior to evaporation of a thin 71Ge layer. Ge is a normal diffuser in aluminium with an activation enthalpy of 119.4 kJ/mol and a pre‐exponential factor of 3.39 × 10−5 m2 s−1. The activation volumes (1.16Ω at 763 K, 1.24Ω at 841 K; Ω denotes the atomic volume) indicate that Ge diffusion proceeds via vacancies. The results are discussed together with work on several other solute diffusers with emphasis on recent studies from our laboratory.

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The pressure dependence of the diffusion coefficients of Co is studied in structurally relaxed meltspun amorphous Fe,,Ni,,B,,.The non-crystallinity of diffusion samples before and after the high-pressure diffusion anneals is checked by X-ray diffractometry. The radiotracer 6oCo is used and ion beam sputtering is employed for serial sectioning of diffusion samples. The activation volume for diffusion is A V = -(0.07 f 0.02) atomic volumes of Co. Within the experimental errors no significant pressure dependence is observed. This observation indicates that Co diffusion in Fe4,Ni40B,, is likely to be mediated by a collective mechanism.Die Druckabhangigkeit der Diffusionskoeffizienten von Co in strukturell relaxiertem, schmelzgesponnenem Fe,,Ni,,B,, wird untersucht. Vor und nach den Hochdruckgliihungen wird durch Rontgenbeugung sichergestellt, dalj die Proben nicht kristallin sind. Als Radiotracer wird 6oCo verwendet zur Schichtenteilung die Ionenstrahlzerstaubung. Das Aktivierungsvolumen der Diffusion betragt AV = -(0.07 -t 0.2) Atomvolumina. Innerhalb der experimentellen Fehlergrenzen wird keine signifikante Druckabhangigkeit beobachtet. Dieses Ergebnis zeigt an, dalj die Co-Diffusion in Fe,,Ni,,B,, wahrscheinlich iiber einen kollektiven Mechanismus erfolgt. IntroductionThe mechanism of diffusion in amorphous metallic alloys is still under discussion [l]. Usually, within the limited temperature range accessible to diffusion measurements and within the experimental accuracy a linear Arrhenius behaviour is observed for the temperature dependence of tracer diffusion coefficients in structurally relaxed amorphous metals indicating a thermally activated process (for a recent collection of data see [2] in [3]). However, both direct as well as indirect (or defect-mediated) mechanisms of atomic diffusion are thermally activated. The observation of radiation enhanced diffusion in amorphous metals has been taken as evidence for diffusion via 'quasi-defects' analogous to the interpretation of radiation enhanced diffusion in crystalline metals [4]. On the other hand, the large variation of the pre-exponential factor and of the activation enthalpy in different alloys and the correlations between them [5 to 71 can hardly be explained in terms of a defect mechanism.Interpreting the small values of the isotope effect parameter and of the vanishing activation volume of Co diffusion in a quaternary amorphous metallic alloy Faupel and coworkers [8 to 101 and independently Frank et al. [5] have promoted the idea of a direct mechanism involving the collective motion of several atoms.Diffusion experiments under hydrostatic pressure have indeed contributed significantly to the understanding of atomic mechanism of diffusion in crystalline metals (see, e.g., [ll, 121). ')