Transport Properties, Microstructure, and Conduction Model of Cosputtered Au–SiO2 Cermet Films

Abstract

High‐resistivity Au–SiO₂ cermet films have been cosputtered. Their transport and structural properties have been examined and a model for electrical conduction is proposed. The electrical resistivity was found to be thermally activated, and the activation energy increased linearly as the metal content decreased. Activation energies varied from 0.01 to 0.07 eV. At a fixed temperature, the resistivity increased exponentially as the weight percent gold decreased. The cermets obeyed Ohm's law. No Hall effect was observed. Transmission electron micrographs showed very small (30–100 Å) discontinuous gold particles separated by very small SiO₂ regions. Films were deposited at 20°, 500°, 520°, and 600°C. Gold particle size increased with increasing gold content or with increasing substrate temperature. Only polycrystalline gold was observed by electron diffraction. The typical infrared spectrum of SiO₂ was recorded. 20°C cermets annealed at 600°C showed large particle growth and twinning. Electrical conduction in Au–SiO₂ cermets is described by a model for conduction in island metal films. Good agreement is obtained between activation energies calculated from measured gold particle diameters and separations, and measured activation energies. From gold particle separations and estimated barrier height, calculations show that charge carriers tunnel through the SiO₂. Many other models were considered, but none fit all the experimental relationships.