Реализация физических подходов к конструированию функциональных металлодиэлектрических систем на основе опалов в фотонике

The possibilities of practical implementation of physical approaches to the design of metal-dielectric photonic crystal systems based on opals, which allow controlling the propagation of electromagnetic waves, are shown. The implemented approaches are based on the effects of excitation of surface plasmon-polaritons capable of propagating along the metal-dielectric interface in plasmonic-photonic layered heterostructures, and modification of the photonic-energy structure of the nanocomposite as a result of dispersion of silver in the opal matrix. Experimental results are presented indicating the occurrence of extraordinary transmission and absorption of light in plasmonic-photonic heterostructures, as well as the asymmetric shape of curves in the reflection spectra of nanocomposites, which is associated with the Fano resonance.

PECULIAR PROPERTIES OF ELECTROMAGNETIC RADIATION PROPAGATION IN PHOTONIC CRYSTALLINE METAL-DIELECTRIC SYSTEMS BASED ON OPALS

The article studies the propagation of electromagnetic waves in metal-dielectric systems based on opals. We revealed anomalous transmission and absorption of light by hybrid plasmon- photonic layered heterostructures associated with the excitation of surface plasmon polaritons propagating along the metal-dielectric interface. The position of maxima in the reflection spectra of nanocomposites, obtained by filling the opal matrix with metal by the electrothermodiffusion method, is explained by the Bragg diffraction, and the asymmetric form of the spectral curves is attributed to the Fano resonance.

Embedding Photoacids into Polymer Opal Structures: Synergistic Effects on Optical and Stimuli-Responsive Features

Opal films with their vivid structural colors represent a field of tremendous interest and obtained materials offer the possibility for many applications, such as optical sensors or anti-counterfeiting materials. A convenient method for the generation of opal structures relies on the tailored design of core-interlayer-shell (CIS) particles. Within the present study, elastomeric opal films were combined with stimuli-responsive photoacids to further influence the optical properties of structurally colored materials. Starting from cross-linked polystyrene (PS) core particles featuring a hydroxy-rich and polar soft shell, opal films were prepared by application of the melt-shear organization technique. The photoacid tris(2,2,2-trifluoroethyl) 8-hydroxypyrene-1,3,6-trisulfonate (TFEHTS) could be conveniently incorporated during freeze-drying the particle dispersion and prior to the melt-shear organization. Furthermore, the polar opal matrix featuring hydroxylic moieties enabled excited-state proton transfer (ESPT), which is proved by spectroscopic evaluation. Finally, the influence of the photoacid on the optical properties of the 3-dimensional colloidal crystals were investigated within different experimental conditions. The angle dependence of the emission spectra unambiguously shows the selective suppression of the photoacid’s fluorescence in its deprotonated state.

Development and study of the process of photonic-crystal film depositing by centrifugation

The article describes one of the promising methods of depositing highly ordered arrays of polystyrene microspheres from colloidal suspension through centrifugation. The simplicity and availability of the method determine the sensibility of its application in the deposition of high-quality ordered photonic-crystal planar structures for devices in nanophotonics, nanoelectronics, sensorics and security systems. A theoretical description of the process of colloidal microspheres self-organization into an ordered structure, the so-called opal matrix, occurring during centrifugation of a suspension is given. The technological equipment and accessories required for the implementation of the method in laboratory conditions are shown. The technological factors affecting the reflection of the formed structures in the region of the photonic band gap have been studied; a mathematical model of the colloidal suspension centrifugation process was developed and analyzed. The main modes of the centrifugation process ensuring an acceptable quality of the samples have been selected.

Structure and emission properties of structures based on carbon walls and aluminum nitride

To create field emission cathodes (autocathodes) used in the manufacture of displays and other devices, carbon nanowalls (CNW) are promising. The CNW layers are a porous material consisting of curved plates formed by graphene layers. The industrial use of CNW autocathodes is impeded by the heterogeneity and instability of the magnitude and density of the cathode current. To improve the characteristics of autocathodes, an AlN film is formed on the surface of the emitting substance, which also has the property of field emission. CNW was obtained from a gas mixture of H2 and CH4 activated by a dc glow discharge. The CNW layers were deposited on silicon substrates and substrates representing a layered structure made by forming an opal matrix (OM) layer on a Si substrate. AlN films with controlled composition and structure were prepared by RF magnetron reactive sputtering. CNW layers with a thickness of > 4 μm were obtained by successive growth of two CNW layers (Si/CNW/CNW structure). An additional CNW layer was also grown on the surface of the first layer coated with Ni (Si/CNW/Ni/CNW structure). AlN films were grown on a CNW layer (Si/CNW/AlN and Si/OM/Ni/CNW/AlN structures). It is shown that CNW plates are formed from graphene layers partially connected by atomic bonds (up to 30 layers) packed in a hexagonal lattice, and AlN films consisted of amorphous and axially textured crystalline phases. The current-voltage characteristics of the autocathodes were measured in a pulsed mode at a pressure of ~10−3 Pa. The Si/CNW/CNW structures are characterized by a threshold of autoemission of ≤ 3.6 V/μm and a high density of centers of emission. The current-voltage characteristics of the layered structures Si/CNW/AlN, Si/OM/Ni/CNW and Si/OM/Ni/CNW /AlN showed better emission properties compared to the Si/CNW structure. The current-voltage characteristics considered make it possible to predict the structure and composition of the emitting layer to improve the operational characteristics of multilayer autocathodes.

Three-dimensional composite nanomaterials based on opal matrixes for electronic devices.

he effect of preparation conditions on the composition and structure of three-dimensional composite nanomaterials based on opal matrixes (packing of spherical particles of amorphous SiO2) has been studied. The experimental part of the work was performed with the samples of opal matrixes with a diameter of spherical SiO2 particles equal ~260 nm. Composite nanomaterials were formed by repeatedly filling of opal matrixes with solutions of metal salts (oxides) and holding the samples at 623–723 K, and after that, they were annealed at 973–1473 K. Chemical reactions and phase transformations of substances in nanopores of opal matrixes depended on the annealing parameters, and chemical properties of intermediate compounds. There was confirmed the formation of SiO2 crystallites in nanopores of composite nanomaterials, as well as the products of their interaction with SiO2. Composite nanomaterials with filling of opal matrix nanopores with metals, ferroelectrics and piezoelectrics, multiferroic and other substances have been obtained. The resulting composite nanomaterials had ordered components (substances) with a given composition and crystallite size in the range of 10–90 nm. The influence of the composition and structure of composite nanomaterials containing ferromagnetically ordered nanostructured magnetic orthovanadates of rare-earth metals, Ni-Zn-Fe-, Co-Zn-Fe-spinel, and also Co and Ni together, on their properties was demonstrated. Present research was executed under financial support by RFBR (Grant N 18-29-02076).

Synthesis and Structural Properties of Nanocomposites Based on Synthetic Opals and Active Dielectrics

This work is devoted to generalize and analyze the previouse results of new photonic-crystalline nanomaterials based on synthetic opals and active dielectrics. Data were characterized by X-ray diffraction and Raman spectroscopy. Active dielectrics infiltrated into the pores of the opal from the melt. The phase structure composition of the infiltrated materials into the pores of the opal matrix were analyzed. The results of x-ray diffraction and Raman spectra allowed to establish the crystal state of active dielectrics in the pores of the opal. The Raman spectra of some opal-active dielectric nanocomposites revealed new bands and changes in band intensities compared to the spectra of single crystals of active dielectrics. Further more, differences in band intensities in the spectra were measured at different spots of the sample‘s surface were observed. The revealed changes were attributed to the formation of new crystalline phases due to the injected dielectrics in opal pores.

Dielectric and Magnetic Properties of Nanocomposites Based on Opal Matrixes, Phosphates and Vanadates of Metals

Opal matrix is a regular 3D-packing of spherical particles of amorphous SiO2, forming an ordered system of voids. Opal matrixes with spherical particles of SiO2 diameter d ≈ 260 nm (Δd ≈ 2 %) were synthesized. The frequency dependences of the conductivity, real and imaginary components of the dielectric and magnetic conductivity of nanocomposites containing crystallites 16–65 nm in size of magnetic materials ‒ double phosphates (LiNiPO4, LiCoPO4) and vanadates (GdVO4 and DyVO4) were measured. The dielectric losses of nanocomposites remain low (at a level of ~ 0.06) in the frequency range 107–1010 Hz for nanocomposites with DyVO4 and LiCoPO4. The dielectric loss increases both in the direction of low frequencies (< 106 Hz) and in the direction of THz frequencies.