Properties of Cermet Films

Abstract

Measurements have bean made of the optical and electrical properties of co-evaporated AgSiOx cermet films. Films varying in metal fraction from 0% to 100% were prepared at a pressure of 5x10 ^-6 Torr and at slow evaporation rates, to give an oxygen rich film. Subsequent exposure to UV light for 8 hours moved the absorption edge of the SiOx to beyond 5.5eV which is characteristic of SiO2. The measurements of reflectance end transmittance were inverted to give the complex dielectric constant by an iterative method using a Kramers-Kronig integral of the transmittance. The results are compared with the Maxwell-Garnett, Bruggeman and Ping Sheng effective medium theories. A previously unreported peak in the imaginary part of the dielectric constant was observed for high volume fraction cermets. The resistivity of the cermets was measured over a wide composition range and a non-metal/metal transition was observed. For some cermets the resistivity was measured as a function of temperature down to 77K. A brief comparison is made with the theories of conduction in cermet films. A number of specially prepared films were examined with a transmission electron microscope.