Conventional and generalized ellipsometric investigation of isotropic spherical and anisotropic ellipsoidal cobalt nanoparticles

Abstract

We propose an optical characterization of complex nanostructured thin layers by spectroscopic ellipsometry. These layers are either made of spherical or ellipsoidal‐shaped cobalt particles buried in a silica thin layer on a silicon substrate. Conventional ellipsometry is used to characterize the optically isotropic layers. It is shown that these implanted layers can be represented by a stack of three sublayers: a Maxwell‐Garnett homogeneous mixture of silica and cobalt clusters sandwiched between two silica sublayers. Ellipsoidal particles are obtained after irradiation of spherical nanostructures by swift heavy ions. In this case, generalized ellipsometry is used to study the uniaxial anisotropic optical effects of these particles. A correlation between the shape anisotropy of the particles and the optical anisotropy of the sample is shown and discussed using generalized Maxwell‐Garnett theory. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)