We have investigated the influence of the Ge wetting layer on both ohmic and scattering losses of a surface plasmon-polariton (SPP) wave in Ag film deposited on SiO2 substrate with an e-beam evaporator. Samples were examined by means of atomic force microscopy (AFM), spectroscopic ellipsometry (SE), two-dimensional X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and microscopic four-point probe (M4PP) sheet resistance measurements. Ag films of 100 nm thickness were deposited at 180 and 295 K directly onto the substrates with or without a Ge interlayer. In AFM scans, we confirm the fact that the commonly used Ge adhesion layer smooths the surface of Ag film and therefore reduces scattering losses of the SPP wave on surface roughness. However, our ellipsometric measurements indicate for the first time that segregation of Ge leads to a considerable increase in ohmic losses connected with a boost of the imaginary part of Ag permittivity in the 500-800 nm spectral range. Moreover, the trend develops over time, as confirmed in a series of measurements performed over an interval of three months. XPS analysis confirms the Ge segregation to the Ag free surface and most probably to grain boundaries. M4PP measurements show that the specific resistivity in Ag films evaporated on a Ge interlayer at 295 K is nearly twice as high as in layers deposited directly on a SiO2 substrate. The use of an amorphous Al2O3 overlayer prevents Ge segregation to free surface.

Cd 1-x Be x Se and Cd 1-x Mg x Se solid solutions were grown from the melt by the high pressure Bridgman method. Optical, luminescence and photothermal properties of these materials were investigated. Spectroscopic ellipsometry was applied for determination of the spectral dependence of the complex dielectric function ( ) E ε and refractive index n(E) at room temperature in the photon energy range 0.75-6.5 eV for samples with optic axis (c-axis) perpendicular to the air-sample interface. The critical point (CP) parameters for E 0 and E 1 transitions were determined using a standard excitonic CP function to fit the numerically calculated differential spectra ∂ 2 ε 2 /∂E 2 . The dispersion of the refractive index of the alloys was modelled using a Sellmeier-type relation. The values of fundamental and exciton band-gap energies were estimated from the ellipsometric and photoluminescence measurements. The origin of luminescence in Cd 1-x Be x Se and Cd 1-x Mg x Se was discussed.

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Plasmonic metamaterials and metasurfaces are important for many linear\ud and nonlinear photonic applications. Here, the possibility to control a nanostructured\ud layer spontaneously formed near an interface of a thin silver film is\ud shown, where the interplay between a grain boundary structure and surface\ud segregation of germanium atoms leads to encapsulation of the grains and,\ud as the result, formation of a composite metamaterial near the film surface.\ud This Ag/Ge composite exhibits strong localized surface plasmon resonances\ud at Ge-encapsulated silver grains, leading to extraordinary second harmonic\ud generation for both transverse magnetic and transverse electric polarized\ud fundamental light with up to two orders of magnitude enhancement compared\ud to thin Ag films without Ge atoms. Segregation phenomena open the\ud possibility for fabrication of a new class of composite materials and gives\ud additional degree of freedom in designing optical properties of nanostructured\ud metamaterials