Diffusion and structural relaxation in compositionally modulated amorphous metal films

The interdiffusivity in compositionally modulated (λ≈25 Å) amorphous (Pd85Si15)61/(Fe85B15)89 and (Pd80Au7Si13)70/Fe30 films has been measured by monitoring the satellite of the (000) x-ray scattering peak during isothermal anneals in the range 210–250 °C. Diffusivities as low as 10−22 cm2 s−1 have been measured. It was observed that the diffusivity decreased continuously during the annealing as a result of structural relaxation and settled down to a constant value only after many hours of annealing. The activation energy of the isoconfigurational diffusivity in the Pd-Au-Si/Fe films is 167 kJ mol−1. This value and the time scale of the relaxation are similar to those observed in earlier viscosity measurements, indicating a similarity between the structural defects controlling both transport processes.