Optical and electrical properties of thin silver films grown under ion bombardment

Abstract

The structure of thin silver films, grown under varying conditions of ion bombardment, are compared by means of their measured structural, optical, and electrical properties. Both the x-ray diffraction results and the dielectric-function measurements suggested that there are voids in our films and that their volume fraction depends on the energy delivered to the substrate during growth. Furthermore, the same dependency on energy was found for the amount of gas atoms trapped in the films, but the low percentage suggests that this cannot have a major influence on the structure or other properties. However, the gas atoms can contribute to an expansion of the lattice by increasing the separation of the metallic grains and increasing the volume fraction of voids. The dc electrical conductivity was interpreted from the microstructure and optical data with a model including scattering at grain boundaries, the fraction of voids and the bulk conductivity. In particular, a comparison between theoretical and experimental data suggest that the electron reflection coefficient at the grain surfaces is not constant, but depends on the condition of film growth.