Étude expérimentale de la diffusion des électrons de conduction par les défauts superficiels de couches minces d'or

Abstract

Polycrystalline thin gold films are grown under vacuum by successive depositions of metal layers. Their electrical resistivity is interpreted in terms of Fuchs-Sondheimer and Cottey-Halpern theories. For recrystallised samples, these models yield values near 0.3 for the diffusion parameter of conduction electrons by the surfaces. Their bulk resistivity at 20°C is found to exceed that for pure perfect gold by some tenth of microΩ cm. Unrecrystallized layers have large thickness inhomogeneities; consequently their electrical resistance cannot be directly described by the theoretical models used here. The variations of electrical resistance measured when adding a small amount of gold on the free surface of a recrystallized gold film are studied in details. They are explained in terms of diffusion of the conduction electrons by the surface defects created in this. process. The growth mechanism of the film is shown to depend on the state of the free surface, residual gas in the vacuum chamber and substrate temperature. A schematic model for growth process is given to account for oscillations of the diffusion parameter observed during the deposition of the first monolayers of metal.