Improved effective medium approach:: Application to metal nanocomposites

An improved effective medium approximation (EMA) is presented that accounts for higher order interactions between metal nanoparticles in metal-dielectric composite materials and compared to experimental results. The theoretical results of this formalism are applied to a composite material consisting of spherical gold nanoparticles randomly distributed in a dielectric matrix, which has been extensively characterized with respect to its structural and optical properties. The experimental results and theoretical predictions are compared and the results are discussed. It is shown that the modified theory expands the range to which EMA can be applied to a metal filling fraction of similar to 20% at very little additional computational expenses. The improved theory also allows extracting more information from the optical characterization of the composite material such as the distribution of the interparticle distances in a composite. (c) 2007 American Institute of Physics.