Measurements were made of the diffusivity of ion-implanted Au in the amorphous material at temperatures which were just below the glass-transition temperature. The concentration profiles, before and after annealing, were determined by using Rutherford back-scattering spectrometric techniques. It was found that the diffusivity in as-quenched material decreased to an equilibrium value. The equilibrium values of diffusivity exhibited a very marked temperature dependence, and could be described by:

D(m2/s) = 1.7 x 1017exp[-413(kJ/mol)/RT]

The results were compared with the viscosity of the same material, and revealed a breakdown of the Stokes-Einstein relationship. It was found, by cycling between various equilibrium values of the diffusivity, that when the material had reached a fully relaxed state the relationship between viscosity and diffusivity was lost.

P.A.Duine, J.Sietsma, A.Van den Beukel: Physical Review B, 1993, 48[10], 6957-65