Browsing by Author "Rashkovskiy, A. Y."

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    The confinement of phonon propagation in TiAlN/Ag multilayer coatings with anomalously low heat conductivity
    (American Institute of Physics, 2016-06-03) Kovalev, Anatoly I.; Wainstein, D. L.; Rashkovskiy, A. Y.; Gago, R.; Soldera, F.; Endrino, José L.
    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.
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    Interface-induced plasmon nonhomogeneity in nanostructured metal-dielectric planar metamateria
    (Hindawi Publishing Corporation, 2015) Kovalev, Anatoly I.; Wainstein, D. L.; Rashkovskiy, A. Y.; Gago, R.; Soldera, F.; Endrino, José L.; Fox-Rabinovich, German S.
    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.
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    Spatio-temporal behaviour of atomic-scale tribo-ceramic films in adaptive surface engineered nano-materials
    (Springer Research, 2015-03-05) Fox-Rabinovich, German S.; Kovalev, Anatoly I.; Veldhuis, Stephen C.; Yamamoto, K.; Endrino, José L.; Gershman, I. S.; Rashkovskiy, A. Y.; Aguirre, M. H.
    Atomic-scale, tribo-ceramic films associated with dissipative structures formation are discovered under extreme frictional conditions which trigger self-organization. For the first time, we present an actual image of meta-stable protective tribo-ceramics within thicknesses of a few atomic layers. A mullite and sapphire structure predominates in these phases. They act as thermal barriers with an amazing energy soaking/dissipating capacity. Less protective tribo-films cannot sustain in these severe conditions and rapidly wear out. Therefore, a functional hierarchy is established. The created tribo-films act in synergy, striving to better adapt themselves to external stimuli. Under a highly complex structure and non-equilibrium state, the upcoming generation of adaptive surface engineered nano-multilayer materials behaves like intelligent systems - capable of generating, with unprecedented efficiency, the necessary tribo-films to endure an increasingly severe environment.