Grain boundary diffusion through thin evaporated films and ion-plated films (500nm thick) was studied at 150 to 250C. Two methods were independently used to determine the diffusion parameters. These were the so-called first-appearance method and the simplified accumulation method. The values of the activation energies and diffusivities were determined from Arrhenius plots:

ion-plated:     D (cm3/s) = 2.3 x 10-5 exp[-0.68(eV)/kT]

evaporated:     D (cm3/s) = 4.6 x 10-6 exp[-0.79(eV)/kT]

The change in activation energy and diffusivity with Sn concentration was tentatively attributed to changes, in the thermodynamic properties of the samples, which occurred during grain boundary diffusion.

A.Bukaluk: Surface Science, 1989, 213, 464-80