Optical properties of thin films with plasmonic effect for light scattering

Abstract

Thin films of Al2O3 with embedded Cu and Ag nanoparticles (NPs) are deposited by r.f. co-sputtering on glass substrates. The samples are annealed at 400°C and 500°C for 3 h in forming gas (N 2+5% H2) to stimulate Cu and Ag nanoclusters' formation. Multilayer structures (stacks) such as Al2O3/Ag/Al 2O3, ZnO:Al/Ag/ZnO:Al and Ag/ZnO:Al/Ag/ZnO:Al are deposited on glass substrate by consequently sputtering of the individual layers. Before deposition of the capping layers of Al2O3 and ZnO:Al, the bi-layer structures are annealed in vacuum for 50 min at 220°C or 400°C in the case of glass/Al2O3/Ag, and at 220°C in the case of glass/ ZnO:Al/Ag and glass/ Ag/ZnO:Al/Ag. The diffuse and specular reflectance and transmittance spectra are measured in the spectral range of 300-1200 nm to study the plasma resonance of Cu and Ag nanoparticles. The optical properties of the films and the stack structures are discussed.