Comparative analysis of optical properties of gold and silver clusters embedded in an alumina matrix

The optical properties of nanocomposite thin films of gold and silver clust ers embedded in an alumina matrix have been investigated The samples have b een characterized by several techniques in order to determine their composi tion, morphology and cluster size distribution. Ellipsometry and photoabsor ption measurements have been performed. The differences in the optical prop erties of the various samples reflect finite size effects. Time Dependent L ocal-Density-Approximation (TDLDA) calculations, taking into account the d- electrons and matrix screening effects, are consistent with observed size e volutions of the Mie frequency. Low frequency Raman scattering spectra exhi bit a strong size-dependent band related to quadrupolar vibration modes of the clusters. (C) 1999 Acta Metallurgica Inc.