Far- and Mid-Infrared Properties of Metal-Insulator Composite Materials

摘要

The goal of this research program was to investigate the infrared properties ofmetal-insulator granular composite materials in order to better understand the relationships between the observed electromagnetic properties, particularly the absorption, and the underlying physical mechanisms. There are several contributions to the observed infrared behavior of a composite material. First is the optical behavior of the individual metallic and insulating grains that make up the material. An important issue is the dependence of these properties on particle size due to boundary effects, quantum size effects, etc. The shapes of the particles is also important. Second is the effect of composition. The electromagnetic properties of a metal and an insulator differ greatly. The infrared properties of the composite material will clearly depend on the volume fraction of metal. The percolation threshold, which specifies the composition for the onset of electrical conduction for a conductor mixed with an insulating host, is a fundamental parameter that characterizes the composition dependence.