Ilya A. Ryzhikov

A laminate of ferromagnetic films with high effective permeability at high frequencies

The paper reports on development of magnetodielectric material with high microwave permeability. The material is a laminate of multi-layer permalloy films deposited onto a thin mylar substrate by magnetron sputtering. The deposited films are arranged into a stack and glued together under pressure to obtain the laminate. With the content of ferromagnetic component in the laminate being 22 % vol., its measured quasistatic permeability is 60. The peak value of imaginary permeability attains 50 and the peak is located near 1 GHz. As compared with the multi-layer films, which the laminate is made of, it exhibits lower magnetic loss tangent at frequencies below the magnetic loss peak and may therefore be useful for many technical applications. Lower low-frequency loss may be attributed to pressing of the glued sample. This rectifies wrinkling appearing due to sputtering of rigid multi-layer film onto flexible mylar substrate and, therefore, makes the magnetic structure of the film more uniform.

Structure of and electric conduction in metal–polymer poly- para -xylylene–Ag nanocomposite films

The processes of formation of metal-polymer poly-para-xylylene-Ag nanocomposites by solidphase cryochemical synthesis are studied. The temperature dependences of the electrical resistivity of the composites measured in the course of polymerization, which involves heating the cocondensate of p-xylylene monomer and metal particles, and on completion of the polymerization are presented. The findings are correlated to the results of the structural investigation of the obtained composite by the atomic-force microscopy, transmission electron microscopy, and x-ray diffraction. An empirical model of the process of nanocomposite formation is proposed. The mechanisms of electric conduction in nanocomposites are discussed.

Influence of substrate on the high-frequency permeability of thin iron films

The ferromagnetic resonance (FMR) spectra of thin metallic films obtained by magnetron deposition on polymeric and ceramic substrates are investigated in the strip line at frequencies of 0.13–12 GHz via frequency and external magnetic field sweeping. The influence of mechanical stresses on the FMR spectra of films deposited on an elastic (polyethylene rephthalate) substrate is discussed. The magnetostriction contribution to the anisotropy field of a film, as well as the influence of tensile stresses on the quasi-static permeability and FMR frequency, is estimated. It is demonstrated that the microwave properties of a thin metallic film are also specified by the properties of the substrate with such a film. A distinction in the magnetic properties of films with the same composition, which are deposited on different substrates, is explained in terms of the magnetostriction effect.

Prospects for the application of nanostructured polymer and nanocomposite films based on poly-p-xylylene for micro-, opto-, and nanoelectronics

The experimental results on the synthesis of nanocomposites based on poly-p-xylylene using the gas-phase polymerization on surface are discussed. The data on the structure, electron model, and physicochemical properties of the nanocomposites are presented. The specific properties of the materials under study allow the application in the development and creation of gas chemical sensors, new catalysts, photodetectors, and optical and magnetic media with predetermined permittivities and permeabilities for the polymer optical systems. The possible directions of the further investigation are proposed.

Structural and optical properties of single and bilayer silver and gold films

An experimental study of structural and optical properties of silver and gold thin films, as well as bilayer films based on these metals, has been carried out. To study properties of nanofilms, reflection spectra upon excitation of surface plasmons in the Kretschmann geometry and spectra of ellipsometric parameters have been investigated. The reflection spectra were analyzed using a theoretical model for determining (effective) dielectric constants of the films. The calculated dielectric constants of the films differ from data obtained by ellipsometry. The features in determining dielectric constants by different methods and characteristics of manufactured films in relation to the influence of the substrate are discussed.

Light localization and SERS in tip-shaped silicon metasurface

Optical properties of two dimensional periodic system of the silicon micro-cones are investigated. The metasurface, composed of the silicon tips, shows enhancement of the local optical field. Finite element computer simulations as well as real experiment reveal anomalous optical response of the dielectric metasurface due to excitation of the dielectric resonances. Various electromagnetic resonances are considered in the dielectric cone. The metal-dielectric resonances, which are excited between metal nanoparticles and dielectric cones, are also considered. The resonance local electric field can be much larger than the field in the usual surface plasmon resonances. To investigate local electric field the signal molecules are deposited on the metal nanoparticles. We demonstrate enhancement of the electromagnetic field and Raman signal from the complex of DTNB acid molecules and gold nanoparticles, which are distributed over the metasurface. The metasurfaces composed from the dielectric resonators can have quasi-continuous spectrum and serve as an efficient SERS substrates.

Effect of Perpendicular Anisotropy and Eddy Currents on the Microwave Performance of Single-Layer and Multi-Layer Permalloy Films

In this letter, microwave and magnetostatic measurements of single- and multilayer Permalloy films are made to find physical reasons causing the decrease of the microwave permeability of the films with increase in film thickness. The permeability is measured in the frequency range of 0.1-10 GHz by a coaxial technique. From the measured permeability, a contribution to the effective field from the magnetoelastic effect is determined. The decrease of microwave permeability in thick films is shown to arise mainly due to the perpendicular magnetic anisotropy rather than from the effect of eddy currents, as is frequently suggested. It is also shown that both these effects are reduced in multilayer films comprising alternating magnetic and dielectric layers. Therefore, such films are promising materials for developing magnets that possess high permeability at high frequencies.

Enhancement of SERS signal using new material based on cerium dioxide facet dielectric films

In this paper, we investigate the potential of facet structures of cerium dioxide for the purpose of increasing the intensity of the surface enhancement Raman scattering (SERS) signal. During the studies, a new metamaterial is developed. The metamaterial is based on facet cerium dioxide films and plasmonic nanoparticles that are immobilized on its surface. The new metamaterial provides an additional SERS signal amplification factor of more than 200. Thus developed material offers the prospect of increasing the sensitivity and selectivity of biochemical and immunological analysis.

Influence of the magnetoelastic effect on the microwave magnetic properties of Fe-N thin films

The microwave permeability of nitrogen-doped iron films deposited on a flexible lavsan substrate has been experimentally investigated. The measurements were performed with the use of a coaxial transmission line. The coaxial samples were coiled from a flexible film in two different ways: with the deposited layer facing outward and with the deposited layer facing inward. It has been found that the measured frequency dependences of the permeability of the two samples strongly differ. A comparison is made between the microwave permeabilities measured in the coaxial transmission line and in a strip transmission line, in which planar samples were used. It is shown that investigation of the influence of the magnetoelastic effect on the magnetic properties at microwave frequencies can provide additional information on the magnetic structure of the material.

Electrochemical corrosion of thin ferromagnetic Fe—N films in neutral solution

A model experiment was conducted in order to determine an interplay between inherent strains and electrochemical corrosion rate in nitrogen-doped iron thin films. 150 and 300 nm thick films, used in the experiment, were obtained by means of DC magnetron sputtering. In order to study the influence of substrate on inherent strains in metal, these films were deposited onto flexible polymer and rigid glass substrates. It was found, that the rigidity of the substrate increased the corrosion rate of thin iron films in a neutral electrolytic solution. It was proven using X-ray diffraction, that the greater rigidity was, the stronger were the internal strains within the films. That effect was especially pronounced in thinner films, where the increase in the rate of dissolution was accompanied by a localization of corrosion. Characteristics of electrochemical processes were measured using a three-electrode cell. The comparison of the films free surface energy was performed by measuring water contact angle.