Interface-Induced Plasmon Nonhomogeneity in Nanostructured Metal-Dielectric Planar Metamaterial

Transformations of the electronic structure in thin silver layers in metal-dielectric (TiAlN/Ag) multilayer nanocomposite were investigated by a set of electron spectroscopy techniques. Localization of the electronic states in the valence band and reduction of electron concentration in the conduction band was observed. This led to decreasing metallic properties of silver in the thin films. A critical layer thickness of 23.5 nm associated with the development of quantum effects was determined by X-ray photoelectron spectroscopy. Scanning Auger electron microscopy of characteristic energy losses provided images of plasmon localization in the Ag layers. The nonuniformity of plasmon intensities distribution near the metal-nitride interfaces was assessed experimentally

Influence of electronic structure, plasmon-phonon and plasmon-polariton excitations on anomalously low heat conductivity in TiAlN/Ag nanoscale multilayer coatings

TiAlN/Ag multilayer coatings with different number of bilayers and thicknesses of individual layer were fabricated by DC magnetron sputtering. Thermal conductivity and electronic structure features were measured on a set of samples with different number of bilayers and individual layer thickness from a 5-150 nm for total coating thickness of ∼0.5 or 1 μm. It was found that thermal conductivity of the multilayer insulator/metal structure becomes lower than for monolithic TiAlN coatings with the same thickness when Ag layers are thinner than 25 nm. The physical nature of thermal barrier properties of the nanolaminate TiAlN/Ag films is studied using X-ray photoelectrons (XPS) and high-resolution electron-energy loss (HREELS) spectroscopies. Based on these results, a physical model for the anomalous decrease in heat conductivity for nanoscale multilayers was developed on base of analysis of plasmon and lattice vibrations inside the layers and at the interfaces. Anomalously low heat transfer is attributed to attenuation of longitudinal acoustic phonons vibrations, decreasing of plasmon-polariton penetration on interfaces, and plasmon states splitting in Ag nanolayers due to confinement effects at multilayer coatings nanostructuring.The reported study was partially supported by Russian Scientific Foundation grant #14-12-00170, RFBR research project

The confinement of phonon propagation in TiAlN/Ag multilayer coatings with anomalously low heat conductivity

TiAlN/Ag multilayer coatings with a different number of bilayers and thicknesses of individual layers were fabricated by DC magnetron co-sputtering. Thermal conductivity was measured in dependence of Ag layer thickness. It was found anomalous low thermal conductivity of silver comparing to TiAlN and Ag bulk standards and TiAlN/TiN multilayers. The physical nature of such thermal barrier properties of the multilayer coatings was explained on the basis of reflection electron energy loss spectroscopy. The analysis shows that nanostructuring of the coating decreases the density of states and velocity of acoustic phonons propagation. At the same time, multiphonon channels of heat propagation degenerate. These results demonstrate that metal-dielectric interfaces in TiAlN/Ag coatings are insurmountable obstacles for acoustic phonons propagation

Interface-induced plasmon nonhomogeneity in nanostructured metal-dielectric planar metamaterial

Transformations of the electronic structure in thin silver layers in metal-dielectric (TiAlN/Ag) multilayer nanocomposite were investigated by a set of electron spectroscopy techniques. Localization of the electronic states in the valence band and reduction of electron concentration in the conduction band was observed. This led to decreasing metallic properties of silver in the thin films. A critical layer thickness of 23.5 nm associated with the development of quantum effects was determined by X-ray photoelectron spectroscopy. Scanning Auger electron microscopy of characteristic energy losses provided images of plasmon localization in the Ag layers. The nonuniformity of plasmon intensities distribution near the metal-nitride interfaces was assessed experimentally.This research was partially supported by RFBR Research Project no. 14-08-00472_a, RSF Research Project no. 14-12-00170, and Russian Federation President Scholarship no. 2040.2012.1. Additional support from Grant FIS2012-38866-C05-05 (Ministerio de Economía y Competitividad, Spain) is also acknowledged. F. Soldera acknowledges the EFRE Funds of the European Commission for support of activities within the AME-Lab project