Growth behavior and optical properties of metal-nanoparticle dispersed dielectric thin films formed by alternating sputtering

Abstract

Volmer-Weber type island growth mode was adopted to form nano-sized metal particles embedded in a dielectric matrix by the alternate deposition of metal and dielectric layers. Particle size and volume fraction were controlled by changing the nominal thickness of the metal layer and its ratio to that of dielectric layer, respectively. For comparison, the Au cluster formation was investigated in detail in both co-sputtered and alternatively sputtered films. Plan-view and cross-sectional transmission electron microscopy experiments combined with the optical absorption near the surface plasmon band show that well-defined An metal spheres can be obtained by alternating sputtering, while closely spaced small particles, some connected and losing their sphericity even in the small volume fraction, are formed in the co-sputtered films. Their size was controlled by the volume fraction. The optical constants of the alternatively sputtered composite films were determined from spectroscopic ellipsometry measurements through the Maxwell-Garnett effective medium model fitting, considering the size dependent mean free path limitation of the free electrons. There was good agreement between simulated and measured optical spectra for the as-grown films. (C) 2003 Elsevier B.V. All rights reserved.