Dielectric and optical properties of CaCu3Ti4O12 thin films containing Ag nanoparticles

Simple sol-gel techniques are used to prepare thin films of a high dielectric constant perovskite CaCu₃Ti₄O₁₂, containing different amounts of metallic silver nanoparticles. The formations of the silver nanoparticles are verified by X-ray diffraction, scanning electron microscopy, transmission electron microscopy and optical absorption studies. The dielectric properties are found to be significantly affected by the presence of the silver nanoparticles. A maximum in the dielectric constant is observed at an intermediate metal particle concentration. This is explained in terms of the polarization at the particle-dielectric interface and the internal barrier layer capacitor effect. The optical absorption spectrum is compared with Mie theory in electrodynamics for the optical absorption of small particles to extract the particle size of the silver particle. Non-uniform distributions of Ag particles through the thickness of the thin films are reported.