Understanding solid state diffusion in multilayered structures on a picometer lengthscale

Multilayered Extreme UV mirrors present unprecedented fundamental questions to solid state diffusion, requiring understanding of diffusion phenomena on lengthscales of only picometers. Using x-ray diffraction applied in situ during thermal annealing, we have investigated diffusion processes well below the Tammann temperature. Resolving picometer structural changes in Mo/Si multilayers reveals diffusion limited compound interface growth, exhibiting Arrhenius-like diffusion behaviour with a reduced activation energy connected to diffusion in the nano-crystalline layers and interfaces. These results are relevant for controlling diffusion processes on a picometer length scale, with potential spin-off to many other thin film applications.