Diffusion in nanodisperse layered film systems

The results of studies on diffusion in a layered Cu-Au film system of a variable thickness (20–3 nm) obtained by the methods of electron diffraction, X-ray diffraction, and resistance measurements are given. It has been found that, regardless of the order in which the components are condensed on a substrate, a variable-composition alloy is formed in the contact area even when the substrate is at room temperature. The estimates made on the basis of the data obtained demonstrate that at the characteristic size of the structural elements of the components equal to 2 nm, the effective coefficient of the copper diffusion into gold is ∼10−15 cm2/s, which is much larger than the values known for macroscopic samples. This indicates that the decisive role in the preparation of these systems is played, along with the condensation-induced diffusion processes, by the smallness of the characteristic size, leading to a considerable decrease in the energy of vacancy formation and the corresponding growth of the diffusion coefficient.