Diffusion-induced recrystallization in nickel/palladium multilayers

In size-mismatched thin film interdiffusion couples diffusion-induced recrystallization (DIR) occurs rather than conventional Fickian atomic transport. Grains formed in this process have characteristic composition levels that are so far not understood. In this work, DIR is studied in sputter-deposited Ni/Pd films. By pre-alloying one side of the diffusion couple, the mismatch, and thus the driving force, are varied. After heat treatment, transmission electron microscopy, energy-dispersive X-ray spectroscopy and X-ray diffractometry demonstrate recrystallization. Characteristic concentration levels are derived from X-ray diffraction data. Remarkably, the concentration inside newly formed grains shifts coherently to the concentration inside the parent layers. We demonstrate that the observed concentration levels are in agreement with a recently published thermomechanical model.