21st International Young Scientists Conference Optics and High Technology Material Science - SPO 2020 ONLINE

25 Sep 2020, 09:00 → 26 Sep 2020, 18:00 Europe/Kiev

Online (Taras Shevchenko National University of Kyiv)

The 21st International Young Scientists Conference Optics and High Technology Material Science - SPO 2020 will be held on September 25-26, 2020, at the new ONLINE format.

The SPO 2020 ONLINE conference's purpose is to bring together students, scientists, and engineers involved in research and development of technologies related to optics and high technology material science. We welcome researchers involved in optics, photonics, applied physics, and engineering. We hope that this Conference will permit us to connect our joint effort to strengthen the role of high optical education in modern industrial society.

The poster session will be held in the next format. All participants must upload their poster on Google Drive ( https://drive.google.com/drive/folders/1cT-YvuNODg8NU721H8v_pTwMts7oSuda?usp=sharing ) until Saturday and make a shortly 3- minute oral presentation via Zoom in Saturday, also another participant would have 1 minute for questions about the presenters work.

Zoom link for participate (not for oral speakers) : https://osachapter.zoom.us/j/91094313457

Friday, 25 September

10:00 → 10:40 Morning Session: Opening

Convener: Prof. Leonid Poperenko (Taras Shevchenko National University of Kyiv, Faculty of Physics, Chair of Optics)

10:00 Opening

Speaker: Prof. Leonid Poperenko (Taras Shevchenko National University of Kyiv, Faculty of Physics, Chair of Optics)

10:10 Ferromagnetic/graphene/ferroelectric nanostructures as a promising non-volatile spin filters and spin valves.

We calculated [1] a spin-polarized conductance in the almost unexplored nanostructure "high temperature ferromagnetic insulator/ graphene/ ferroelectric film" with a special attention to the control of electric polarization direction and value in a multiaxial ferroelectric film by a misfit strain. We proposed a phenomenological model taking into account the shift of the Dirac point due to the proximity of ferromagnetic insulator and using the Landauer formula for the conductance of the graphene channel. We derived analytical expressions, which show that the strain-dependent ferroelectric polarization governs the concentration of two-dimensional charge carriers and Fermi level in graphene in a self-consistent way.
Due to essential spin asymmetry of the band spectrum of graphene channel, imposed by ferromagnetic, the obtained results demonstrate the realistic opportunity to control the spin-polarized conductance of graphene by a misfit strain at room and higher temperatures in the nanostructures CoFeO4/graphene/PZT and Y3Fe5O12/graphene/PZT, and so open the possibilities for the applications of ferromagnetic/graphene/ferroelectric nanostructures as non-volatile spin filters and spin valves.

[1]. Anna N. Morozovska, Eugene A.Eliseev, Maksym V.Strikha. Strain engineering of ferromagnet-graphene-ferroelectric nanostructures // Physical Review Applied. – 2020. - Vol. 14, No. 2. –article number 14.024081.

Speaker: Maksym V. Strikha (Taras Shevchenko Kyiv National University)

10:40 → 13:00 Morning Session: Talks from Shizuoka University

Convener: Mr Serhii Derenko (Taras Shevchenko National University of Kyiv)

10:40 TlBr Photon Counting X-ray imager

TlBr has been recently studied as a compound-semiconductor radiation detector operating at room temperature, because of its large atomic number (Tl:81, Br:35), high density (7.56 g/cm3) and large band gap of 2.68 eV, which makes it suitable for room temperature operation, it has the necessary low thermal noise. In addition, it has a low melting point of 460°C, which facilitates crystal growth, and direct growth on LSI substrates can be expected. The resistivity is as high as 10^10Ωcm with very low leakage current, making it a good semiconductor material for radiation detectors, which is suitable for photon counting methods to detect pulse per photon. However, it has a problem of ionic conductivity and its properties deteriorate over a long period of time, and it has been reported that the time degradation characteristics can be improved by using a Tl electrode.
In this study, by applying the latest 3D-IC fabrication technology, we have fabricated an X-ray imaging device by bonding the TlBr crystals to our original signal readout LSI. The signal processing method converts the charge generated in the TlBr semiconductor X-ray detector directly from the charge to a digital signal without converting it to a voltage. This combination has resulted in a photon counting TlBr X-ray imaging device. We were able to capture X-ray transmission images in test imaging. Challenges and their solutions in long-time operation are also discussed.

Speaker: Prof. Toru Aoki (Shizuoka University)

11:05 Thermal Stability of Electrical and Spectral Properties of CdTe X-ray Detectors with a Schottky Barrier and Laser Doping p-n Junction

CdTe has been used as an X-ray image detector because of its high sensitivity, energy and spatial resolution, and room temperature operation. In order to build image detectors, it is necessary to bond CdTe pixel elements to a signal-reading LSI, and it is necessary to maintain the performance even if it is added heat treatment in order to use an efficient method for making contacts with the substrate. The thermal stability of two types of In/CdTe/Au diode detectors with a p-n junction or a Schottky barrier are examined. p-n junctions were formed by by irradiating a laser beam onto the interface between the indium (In) metal electrode and CdTe and doping In atoms into CdTe. The Schottky barrier is formed at the interface between the p-type CdTe semiconductor and the In metal electrode. In the case of the p-n junction CdTe detector, the I-V characteristics did not deteriorate even after adding heat treatment at temperatures up to 300 °C above the melting point of In (156 °C), and the γ-ray detection efficiency and energy resolution did not change. On the other hand, in the case of the Schottky barrier CdTe detector, the I-V characteristics and the spectral characteristics deteriorated with increasing temperature and the sensitivity to γ rays was lost.The thermal stability of the CdTe detector was found to be improved by irradiating the interface between the electrode and CdTe with a laser beam. The thermal stability of the electrode and CdTe indicates the formation of a p-n junction.

Speaker: Mr Amane Ohno (Shizuoka University)

11:15 Subjective Evaluation of Color reproduction by Color Adjustment of UHD-TV Displays

The standard for imaging equipment called UHD, has features such as high resolution, wide color gamut, and wide dynamic range compared with standard for HD. wide color gamut displays such as UHD compatible displays has been considering for application not only in the entertainment field but also in the medical and industrial fields. It is considered important for imaging equipment used in the entertainment field to give a good impression to the user, and color adjustment is performed. In the medical and industrial fields, image devices are subject to subjective inspection using the colors displayed on the display. It is desired to express the same color as a person sees on display in the medical and industrial fields. It is said that when color adjustments such as those used in the entertainment field are performed in the medical and industrial fields, it leads to misjudgment. According to the UHD standard, it meets 99% of naturally occurring reflected colors. It is difficult for UHD-compatible image equipment to sufficiently satisfy the color gamut defined as a standard due to the problem of the light emitting element. Trying to display a color outside the color range of the display, it tries to display by clipping the color outside the color range of the display. In this study, color adjustment by clipping the color gamut of the UHD-TV display was subjectively evaluated using UHD-compatible images for color reproducibility when viewed by humans, and the effect on color reproducibility was examined.

Speaker: Mr Ryo Tsuboi (Shizuoka University)

11:30 Materialdiscrimination by spectral X-ray imaging using the photon counting type detector

Photon counting type detectors can record incident photons along with their energy.Spectral X-ray imaging with this photon counting type detectors, which measures X-ray photons with each energy, is expected to identify material and improve contrast by utilizing the interaction with substances that differ depending on the energy of X-rays.Due to the characteristics of the X-ray spectrum, the number of photons is small at higher energy bins, and quantum noise may occur.Moreover, since the permeation ability of a substance is less in the lower energy bins than in the higher energy bins, it may not be possible to measure sufficient number of photons.For these reasons, it is necessary to consider whether the interaction between each energy band data and the substance is correctly reflected when using each energy band data in spectral X-ray imaging, and the influence of quantum noise.In this study,a photon counting type radiation detector was used to identify multiple substances.X-ray transmission images of multiple objects of various thicknesses were imaged using a 160 kV X-ray tube, and the images were constructed from energy data of every 10 keV.In the transmission data of all energies, there were some parts that showed the same degree of transmission despite different substances.Therefore, it was confirmed that different substances can be discriminated by creating data obtained from the difference between two types of energy-specific data, comparing the contrasts, and performing analysis.

Speaker: Mr Tatsuya Suzuki (Shizuoka University)

11:45 Proposal of representation of internal structure of objects using X-ray 3D-CT imaging and virtual reality (AR)

X-ray imaging has been widely used in the fields of medical examinations, non-destructive testing, and security as observing the interior of objects due to its high penetrating power. Spectral CT can provide high contrast even for objects with similar densities, and can distinguish materials by using energy information. On the other hand, the amount of information about interior of objects obtained by multi-slice X-ray CT is much larger than that of visible light 3D images. For that reason, user of X-ray CT as medical professionals and examination technicians have to organize a large amount of information in their minds. For example, physician have to image in their mind the three-dimensional relationships and depth of the actual organs by viewing them on a fixed plane monitor. As a solution to this problem, this study proposes an application that displays data obtained from CT imaging in augmented reality (AR). An application was developed that displays the component of objects in 3D for non-destructive inspection of components. When a user points the object with a camera on the device such as smartphone and tablet, the device recognize objects as an AR marker and the internal image of the part was synthesized on the screen. User can understand the internal structure of the component from various directions by tilting and rotating the device. This study will contribute pseudo 3D color display technology using photon counting X-ray CT imaging.

Speaker: Mr Hiroki Kase (Shizuoka University)

12:00 A study on a new imaging method using photon counting detectors for improving the quality of X-ray images

X-ray imaging is used in variety of fields such as medical, industrial and security fields.
Photon counting type X-ray image detectors have been developed in our group. Compared with current-integration type detectors which is used as a conventional type detectors, photon counting type image detectors can eliminate noise such as thermal noise and leakage current by setting a threshold value for the wave height since count the current pulse generated from each X-ray photon, and can produce transmission images in each energy band. On the other hand, if only signal energy band is used as a transparent image, noise is generated due to photon variations, which makes it difficult to obtain differences in luminance due to the thickness of the object. This study developed an application that can synthesize multiple images in order to change the output ratio of each energy band and make the blurred areas clearer by changing the contrast. As a validation, X-ray transmission images of aluminum plates with different thickness in the range of 10keV to 100keV in every 100keV in every 10keV energy band were imaged. These images have combined by each energy band in an arbitrary ratio and contrast increase or decrease in each pattern was evaluated. As a result, it was confirmed that the visibility of the image was improved by using this method, which indicates the possibility of combining different images by each energy band.

Speaker: Mr Takeru Goto (Shizuoka University)

12:15 Developing an imaging instrument using a small neutron source.

This study is about to developing an imaging instrument using a small neutron source. X-ray penetration image and neutron penetration image have a complementary relationship. The neutron penetration imaging has advantage of structural analysis of materials containing light elements than X-ray penetration imaging, and it can image interior of thick metals due to its very high transmission capability. Currently, all the neutron facilities are large in size. Some of neutron sources are more than 1 km in length, but there is no table-top neutron facility that can be used in a small size. Therefore, the principle verification of the system has been designed and the elemental technology was carried out to develop a neutron penetration imaging device. In order to develop the instrument, design for safety has verified, and then designed the instrument for imaging. Then, the effects on neutron shielding and scattering were simulated. After that, as a proof of principle for the elemental technology, hydrogen plasma generation was confirmed that will lead to the experiment of actual generation of neutrons.

Speaker: Mr Kazuma Matsumoto (Shizuoka University)

12:30 Reconstruction of Energy Integrating by Photon Counting for High Dynamic Range X-ray Imaging

Photon counting, which measures the energy information of X-ray photons, is an advanced imaging technique in X-ray imaging. One of the merits compared with the conventional energy integrating detectors is the high sensitivity for detecting individual X-ray photons. On the other hand, the range of detectable doses is limited by the pile-up effect in which the detection of multiple photons overlaps. Energy integrating detectors convert the X-ray dose into electric current and measures it, so contrary to photon counting, the dose can be measured without being affected by the pile-up effect even at high doses, while the current generated by the X-ray is buried in the dark current of the detector under low dose. Therefore, we propose an imaging method that is sensitive to individual X-ray photons but is not affected by the pile-up effect by reconstructing the energy integrating based on the photon counting detector.
There are two important points in this proposal: calculating the energy integrating with photon counting detector and implementing it in a CMOS circuit. The calculation method has been expressed using a weighting function for the energy of each photon. By transforming the weight function for energy integrating, the arithmetic circuit can be adjusted. On the CMOS circuit side, in order to measure from individual photons to current, a Pulse Width Modulator (PWM) that easily increase the dynamic range for electric charge has been used. As the result, a pixel circuit for energy integrating without adder circuit has been realized.

Speaker: Dr Katsuyuki Takagi (Shizuoka University)

13:00 → 14:00 Break

14:00 → 15:35 Afternoon Session

Convener: Mr Mykyta Redkin (Taras Shevchenko National University of Kyiv)

14:00 Deflection enabled multifunctional operation of a simple meta-grating at near-infrared

Deflection, a general wavefront manipulation functionality, which is often considered as a characteristic attribute of gradient metasurfaces, is numerically and experimentally investigated at near-infrared for a simple reflection-mode meta-grating comprising just one Si nanorod per period. Different deflection scenarios are demonstrated that enable different functionalities and multifunctional scenarios in one structure. In particular, single-wave, high-efficiency, ultra-wideband and simultaneously wide-angle deflection is achieved due to the ultimate conversion of the linearly-polarized incident wave to the -1st diffraction order. The working region in the wavelength – incidence-angle plane nearly coincides with the region, in which the -1st order is the only propagating nonzero order. It extends nearly from 850 to 2000 nm and is up to 70 degrees wide. The total thickness of the designed structure does not exceed 0.6 of the free-space wavelength. The obtained results justify the usefulness of the orders higher than the -1st order. Spatial filtering of several types can be achieved by utilizing deflection for one of nonzero orders or the specular-reflection (zero-order) regime. Dual-beam splitting that is yielded by deflection is also demonstrated. Moreover, on-off switching of deflection, spatial filtering, and splitting is possible owing to polarization state change. The proposed device is simple-to-fabricate and only uses cost-effective materials, so it is appropriate for the large-area fabrication by using nanoprint lithography. The possibility of either multifunctional operation or the use of only one functionality makes it a great candidate for various applications in the areas of optical communications, laser optics, sensing, detection, and imaging.

Speaker: Dr Andriy Serebryannikov (Adam Mickiewicz University, Faculty of Physics)

14:25 Compositional dependencies of Raman spectra of Ge-As-Se chalcogenide glasess

Chalcogenide glasses are known as perspective materials of optoelectronics with a high optical transparency in the infrared region of telecommunication windows 3-5 and 8-12 μm. In this work, influence of composition on structural transitions and optical properties of chalcogenide glasses was studied by Raman technique. Obtained Raman spectra chalcogenide system Ge$_{4.5}$.As$_{14.5}$Se$_{81}$, Ge13.5As23.5Se63 and Ge18As28Se54, Ge27As37Se36, Ge30As40Se30 were analyzed using CoRa software. The Ge–Se vibrations in [GeSe4] tetrahedrons occurred at 193 cm–1. The As-Se vibration band generally occurs at around 230 cm–1. In the higher frequency region, there occurred a weak band at 250 cm–1 with a broad shoulder at 300 cm–1, assigned to Se–Se vibrations in Se-chains and asymmetric stretches in [GeSe4], respectively. The existence of Ge–Ge bonds is indicated by the shoulder occurring in the region 170–180 cm–1 at the lower frequency side of the Ge–Se band, assigned to Ge–Ge vibrations in [Se3Ge–GeSe3] structural units. The band at 100 cm–1 is assigned to As–As vibrations, and its shoulder at 130 cm–1 to Ge–As vibrations. As the content of germanium increases, the chance for tetrahedrons [GeSe4/2] meeting each other increases, which is indicated by the occurrence of edge-shared [GeSe4/2] band at 214 cm-1. Thus, the structure of the glasses is described as a mixture of the AsX3/2 and GeX 4/2 , connected either directly or through chalcogen chains and with presence of non-stoichiometric structural units.

Speaker: Mykhailo Popovych (V.E. Lashkaryov Institute of Semiconductor Physics, National Academy of Sciences of Ukraine)

14:40 Experimental conditions for the coupling of random lasing and stimulated Raman scattering of dyes

The random lasing (RL) in the multiple scattering active media can occur together with the stimulated Raman scattering (SRS) and form a quasilinear secondary emission spectrum under conditions of the diffuse light propagation. Under these conditions, the stimulated Raman scattering spectrum obtained from the secondary emission spectrum is a more structural than the spontaneous Raman spectrum. This makes it possible to detect even weak and close located spectral Stokes lines in principle.
We were experimentally investigated the features and experimental conditions for the coupling course of these processes in the multiply scattering media based on the vesicular polymeric films dyed with laser dyes. The intensity of these lines nonlinearly depends on the pump intensity and is proportional to the random lasing intensity at the corresponding frequency and observed only within the random lasing area. The width of the secondary emission spectrum and the SRS lines number which show in it are increase with increasing dye concentration and vesicle concentration. The relative intensity of the SRS lines and RL intensity increase with decreasing temperature to the helium levels, which leads to an increase in the sharpness of the quasilinear spectrum of secondary emission. The SRS lines are show only in the overlap regions of the random lasing spectrum with the Stokes lines location spectral range, which can be established using the pseudo-Stokes spectrum constructed using the infrared absorption spectrum of dye. The SRS occur at all Raman frequencies which find oneself in the RL spectrum range.

Speaker: Mr Andrii Smaliuk (Faculty of Physics of Taras Shevchenko National University of Kyiv)

14:55 Design of two-phase lock-in amplifier

Lock-in amplifiers are widely applied in optical measurements when desired signal buried in noise. In the same time commercial broadband lock-in amplifiers that can make such measurements are expensive. This article presents design of lock-in amplifier that can be used in one-phase, two-phase mode or as two parallel one-phase amplifiers. It is completely digitally-controlled and may be connected to personal computer through USB interface. The structure scheme and electrical circuits of the lock-in amplifier components were developed. Using the automatical design systems such as TINA and Eagle CAD the appliance was simulated and his main characteristics were calculated: maximum sensitivity – 2 μV, minimum – 40 mV; operating frequency range of the input signal from 100 Hz to 130 kHz; accumulation time 0.1 ms, 1 ms, 10 ms, 100 ms, 1 s, 2.5 s, 5 s, 10 s; minimum signal-to-noise ratio is 62 dB, maximum – 75 dB; dynamic reserve not less than 97 dB.

Speaker: Volodymyr Metelov (Taras Shevchenko National University of Kyiv)

15:10 Transport Properties of SOI MOS Transistors

Si-based metal-oxide-semiconductor field-effect transistors (MOSFETs) are widely used in high-density integrated circuits for amplifying and switching electronic signals. MOS transistors produced by the silicon on insulator (SOI) technology yield a high switching speed, reduced power consumption and provide a flexible architecture by varying such parameters as thickness of a Si layer and buried oxide layer, substrate doping and back gate voltage. Due to the device structure and ability to form conductive front and back channels for electrons (holes) under applying a certain voltage to the upper and back gate, the MOSFET systems find its application for modeling a 2-dimentional electron (hole) gas (2DEG, 2DHG) in charge transport research. Electron transport properties of the SOI MOS transistors at low temperatures were studied. Possible electronic processes and electron scattering mechanisms in the channels are discussed.

Speaker: Dr Kateryna Zelenska (Shizuoka University )

15:35 → 16:35 Break

16:35 → 18:50 Evening Session

Convener: Andrii Shcherbakov (Walter Schottky Institute Technical University of Munich)

16:35 Thermalization in a quantum Fermi-Pasta-Ulam-Tsingou problem

We investigate thermalization in a quantum Fermi - Pasta - Ulam - Tsingou problem for anharmonic vibrations in atomic chains applying semi-quantitative analysis of resonant interactions complemented by exact numerical studies. We estimate the energy at transition from the localized low-energy phase to the chaotic high-energy phase. The transition energy is inversely proportional to the number of atoms in the classical regime and reaches a plateau in the quantum regime. Systems with free or fixed ends boundary conditions reach the chaotic regime at lower energies than the periodic systems. We discuss the applications of the theory to realistic molecules and their spectral properties.

Speaker: Dr Andrii Maksymov (IonQ)

17:00 Direct Femtosecond Laser Processing of Pd Surface For Nanostructures Creation

Laser-induced periodic surface structures (LIPSS) are very common phenomena that arises from interaction between different surfaces and femtosecond laser pulses. Characteristic size of such structures is laser wavelength order and typically belongs from nano- to micro-scale range. Searching new material surfaces for the nanostructuring are significant scientific interest of these days. We are reporting on the fabrication of the LIPSS on palladium upon femtosecond laser irradiation, employing laser beam scanning. It is shown that the structures are contained from palladium oxide (PdO). Palladium oxide are useful catalysts for catalytic hydrogenation in organic synthesis. Additionally this material has very high third order nonlinearity. It means that surfaces contained with PdO is very perspective material in optical quantum electronics. Thus, the structure could be useful in scientific researching and industry.

Speaker: Dr A.S. Rybak (Institute of Physics, NAS of Ukraine)

17:15 Short-pulsed laser production of nanomaterials: clusters, nanoparticles, and periodic surface structures

A change in the structure of a material under the action of laser radiation can occur if the energy of light, transmitted to some area of the material, exceeds the energy of interatomic bonds in this area. The magnitude of the excess and the time, during which the energy is transferred, are both important. If the duration of the laser pulse is longer than the time of thermal relaxation, then this area of the material melts and evaporates – nanosecond laser ablation occurs. If the power of the laser pulse is high enough (short duration and high intensity), then electronic nonequilibrium processes start to rule: pico/femtosecond laser ablation takes place. Laser ablated substance consists of hot ions and fragments of the material. Upon cooling, they condense into clusters and nanoparticles (NPs). Besides, under particular conditions the laser induced periodic surface structures (LIPSS) occur on the ablated surface.
Our research is mostly performed on the basis of the Center for Collective Use of Equipment of NAS of Ukraine "Laser femtosecond complex" at the Institute of Physics of NAS of Ukraine. The radiation of Ti:Sa laser system (150 fs, 2 mJ, 1 kHz, 800 nm) is sufficient for ablation of almost any material. Produced LIPSS were visualized by SEM Aura 100, while the morphology of the NPs was studied by TEM-100M. Size of the NPs was checked by a homemade DLS setup. In the report, practical and physical aspects of short-pulsed laser formation of different nanomaterials will be presented.

Speaker: Dr Andriy Dmytruk (Institute of Physics of NAS of Ukraine)

17:30 Overview on laser acoustics

Ultrafast lasers can be used to produce sound waves in a medium. Usually, the laser beam is focused onto the sample that partially absorb the light. The transient heating of the sample produces transient mechanical stresses that lead to ultrasonic transduction. Since the discovery of ultrafast lasers, the generated sound waves have reached ultrafast timescales, in the picosecond regime, with corresponding frequencies in the THz range. Right now, lasers can be used to efficiently excite sound waves at any given frequency up to THz. In the THz frequency range, the ultrasonic wavelength is on the order of a couple of nanometers making them suitable for probing nano-objects. This photoacoustic technique perfectly fits the needs for non-contact, non-invavise, non-destructive mechanical probing of samples. Depending on the laser peak energy, the acoustic pressure can be tuned. With extremely powerful lasers the acoustic pressure can reach TPa. In this case, the intense acoustic wave becomes a so-called shock wave. The experiments are carried out on a single shot basis since the shock wave irrevocably damages the sample.
In the present talk, I will review the latest results which we have obtained dealing with ultrafast acoustics and shock waves.

Speaker: Dr Thomas Pezeril (MIT - CNRS)

17:55 Photoconductivity of GeSn alloys

Germanium tin (GeSn) semiconductors are promising absorber/emission materials for the novel infrared (IR) optoelectronic devices. The main advantage of these materials is the possibility to obtain a higher absorptivity in comparison with indirect-bandgap crystalline silicon, germanium, and their alloys. The GeSn/Ge/Si heterostructures were grown by a chemical vapor deposition method. An intermediate 700 nm thick Ge buffer layer was grown on a boron-doped Si (001) substrate by a two-step growth method to minimize the lattice mismatch between the GeSn epilayer and the Si substrate. The lateral photoconductivity spectral dependencies of GeSn alloy with various content Sn in the 0% <x <20% range were studied at 80-300 K temperatures. The values of the direct and indirect bandgaps were determined by fitting spectral dependencies near the absorption edge. The photosensitivity and carrier lifetimes of the GeSn-based photoresistors of various Sn content were analyzed to propose a mechanism of photoconductivity of GeSn thin films.

Speaker: Mr Serhii Derenko (Taras Shevchenko National University of Kyiv)

18:25 Unusually long carrier lifetime in Mott Insulators: Key property for integration in Mott neurons

The study in non-equilibrium conditions of an emblematic class of quantum materials, the Mott insulators, is currently developing into an active and fruitful branch of solid-state physics. Recent researches indeed demonstrate that Mott insulators excited either by ultrafast infrared or THz laser pulses or by electric fields might display non-trivial insulator to metal transitions (IMT’s) whose origin goes beyond the well-established bandwidth- and filling-controlled mechanisms. Interestingly such transitions could be used to build up new electronics based on Mott insulators, called Mottronics, including breakthrough devices such as Mott memories and artificial neurons for artificial intelligence.

A common feature of out-of-equilibrium IMT’s in Mott insulators is that they are based on the massive excitation of electrons from the Lower (valence) to the Upper (conduction) Hubbard Band. For example, recent studies proposed that the multiplication of carrier in a Mott insulator placed under the electric field occurs either thanks to an impact ionization or to an electronic avalanche.

In this talk, we will present detected unusually long carrier lifetime in the multiband Mott insulator GaV$_4$S$_8$ using the tr-PEEM (time-resolved photoemission electron microscopy) technique. This result is important since it supports the proposed mechanism of electronic avalanche and will guide the future development of new hardware components in artificial intelligence.

Speaker: Mr Danylo BABICH (Institut des Matériaux Jean Rouxel (IMN), Université de Nantes, CNRS)

Saturday, 26 September

11:00 → 13:00 Saturaday Session

11:00 Temperature sensor based on Photonic crystal fiber

In a photonic crystal fiber (PCF), the use of air hole as a core provides the ability to guide light in the air. The light is trapped in the defect in photonic crystal, as an application for this type of fiber, there is the high-energy transfer, endless single mode and fiber sensors, which measure physical parameters (temperature, pressure, force, etc.)

Many numerical tools exist to model the behavior of a PCF. Our choice has been on the finite domain-beam propagation method (FD-BPM). The Beam Propagation Method (BPM) is a numerical modeling method to simulate the propagation of a wave in a guide of arbitrary geometry. It can predict from an incident field distribution within a structure. The main idea of this method is to divide a structure into "slices“ elementary, spacing with ΔZ and then determine the scope of a given slice from the one before. However, the equations to solve are complex, which leads us to adopt certain approximations.

Our contribution in this paper is to show the influence of temperature on dispersion properties of photonic crystal fibers infiltrated with water. This study were done by proving that the temperature had a direct effect on chromatic dispersion by infiltrating the air holes with liquid; we choose water as a liquid because it contains a large part of biological and chemical solutions. However, the dispersion properties of these water-filled PCFs have not been studied extensively.

Speaker: Dr Mohammed DEBBAL (University Center BELHADJ BOUCHAIB)

DEBBAL Mohammed.docx

11:15 GPON-FTTH NETWORK ARCHITECTURE AND DEPLOYMENT FOR RESIDENTIAL CONDOMINIUM

The Optical fiber-based network also known as Fiber To The Home (FTTH) that is the future solution for providing broadband service such as voice, data and video (Triple play).This paper addresses the concept and deployment of Fiber to the Home (FTTH) for residential condominium based on the ITU-T G.984 standard Gigabit passive optical network (GPON) to reach a capacity of the maximum subscribers and more effectively accommodate high bandwidth for triple play services.

Speaker: Mr Mouweffeq BOUREGAA (Mustapha Stambouli University )

BOUREGAA MOUWEFFEQ.pdf

11:30 Analysis of New Design of Graphene Patch Antenna Element for satellite Application

This article presents an analysis of the substrate variation effect for a new design of graphene polygonal patch antenna for Ka-band applications, Where an application of graphene as radiating patch for satellite applications; will be proposed to ensure the proper functioning of this antenna for Ka-band , the effectiveness of graphene planar antenna will proved by a numerical simulation by CST with 3.01 dBi of antenna gain at 20.14 GHz and return loss less than -10 dB for substrate height h=1.575 mm, which gives us the opportunity to invest this antenna in the satellite transmission system.

Speakers: Dr Mohammed Amin Rabah (Algerian Space Agency- Satellite development center), Dr Mohammed Debbal (Belhadj Bouchaib University center AinTemouchent - ALGERIA)

11:45 OPTICAL LOCAL AREA NETWORK SYSTEM DESIGN AND PERFORMANCE

High-speed transmission is essential in telecommunication systems and increases according to the needs of users for various applications such as live broadcasting, video on the Internet, videoconferencing, etc. In this paper, we describe our optical communication network. Moreover, we have shown the influence of several parameters on the transmission quality of Optical Local Area Network (Optical LAN). This study allowed us to optimize the parameters of the networks, which give it possible to save the cost of installation and to add more services on the same network.

Speaker: Dr Mohammed DEBBAL (BELHADJ BOUCHAIB University and Telecommunication Laboratory (LTT))

OPTICAL LOCAL AREA NETWORK SYSTEM DESIGN AND PERFORMANCE.pdf

12:00 Realization of a device for detecting the electrical activity of the brain and the acquisition of the EEG electroencephalogram signal

The brain has always been the master of all human organs, being responsible for all voluntary or involuntary activities. For that, the brain is a subject of a many research such as neurobiology, neurology, psychiatry, psychology, linguistics, anthropology... Among the many methods of exploring the brain, the basic technique is EEG electroencephalography.

The electroencephalogram (EEG) is the recording of the electrical activity of the brain performed on the surface of the head through non-invasive or even invasive electrodes.

From where objective of our thematic is to realize a device that can detect the electrical activity of the brain for diagnostic purposes. Our work rallied two distinct steps, where the first is the electronic design of the EEG device including all its blocks starting with the sensor, a shaping circuit from which the acquisition as well as the recording of the EEG signal are assured by the Arduino card.

The second step consists of processing of the signals recorded on a Matlab programming environment for the purpose of diagnostic assistance.

Keywords: Electroencephalography, brain, EEG signal, arduino card, Matlab

Speakers: Dr Lahouaria BADIR BENKRELIFA (University Center BELHADJ BOUCHAIB, Ain-Temouchent, Algeria; ), Dr Boumedyen BELAID (Abou-Bekr BELKAID University, Tlemcen, Algeria;)

12:15 Design of a Photoplethysmograph in infrared based on an optical sensor

Photoplethysmography (PPG) is an optical measurement for observing changes in blood volume in a tissue non-invasively.

Photoplethysmography in the infrared is based on two principles: the presence of a pulsatile signal generated by the arterial blood and the differential absorption of oxyhemoglobin.

As part of this work, we present a formatting circuit of PPG signal in the infrared. This study is divided into two main parts: an analog part presents the designing of formatting circuit (including a probe formed of an infrared LED and phototransistor, matching circuits, filters, amplifiers…), and in other hand, a digital part designed around an Arduino Uno board built upon the ATmega328 microcontroller exploited for data acquisition.
A Software programming of this board and the development of a data acquisition script allows to record signals in a data file, which are treated in a Matlab environment

Speakers: Prof. Mansouria Sekkal (University Center BELHADJBOUCHAIB), Prof. Lahouaria BADIR BENKRELIFA (University Center BELHADJBOUCHAIB)

12:30 Investigation the optical effects of monochromatic light at 635 nm on human lung and liver tissues using Monte Carlo simulation

In recent decades, light became one of the most versatile components for diagnosis and therapeutic purposes. Advancement in optical science and engineering had led to invention of a wide variety of non-invasive and minimally invasive apparatuses and procedures that are inseparable from today’s medicine; namely OCT, PDT, etc. The common component of all of these methods is propagation of photons in tissue. Unfortunately, in vivo experiments could be dangerous and result in permanent damage such as destruction, burning and ablation of the tissue. To avoid these complications various techniques of light-tissue interactions simulation have been developed to prognosticate the behavior of photons in biological tissue. In this work, we simulated the interactions between human lung and liver tissue under irradiation of infinitely narrow beam of monochromatic light at 635 nm. By using Monte Carlo simulations, optical properties of tissue including refractive index n, absorption coefficient µa, scattering coefficient µs, and anisotropy g, were calculated. Also we studied some physical effects: Fluency, reflectance, transmittance, absorption and penetration depth of this monochromatic light for a 5 mm one-layer phantom of lung and liver tissues. In addition, logarithmic figures were plotted to sketch Fluency and absorption for each phantom and as the results we deduced that all graphs attenuate exponentially through tissues. The light Fluency in liver tissue at 635 nm is higher than lung tissue; and in early stages, absorption of lung tissue is higher than liver tissue, though it reduces rapidly. Penetration depth is deeper for liver tissue and light transmission of lung tissue is zero.

Speaker: Dr Adeleh Granmayehrad (Roudehen Branch,Islamic Azad University)

12:45 EVALUATION IN TRANSPARENT OPTICAL NETWORK ARCHITECTURE WITH PON ACCESS

The evolution of telecommunication networks towards the transport of multimedia data (internet, telephony and IPTV) makes it necessary to seek systems offering high bandwidth and multiple access to resources. The optical network currently represents a reliable solution thanks to the qualities of the fiber (transmission channel) and the development of FTTH (Fiber To The Home) technology and also the establishment of passive optical networks (Passive Optical Network: PON). The "shared optical network" concept saves the cost of fiber and optical components between the various customers connected to the FTTH-GPON network. In this paper, analyzing designing and implementing of FTTH access network based on GPON for residential condominium.

Speaker: Dr MOUWEFFEQ BOUREAA (MUSTAPHA STAMBOULI UNIVERSITY)

EVALUATION IN TRANSPARENT OPTICAL NETWORK ARCHITECTURE WITH PON ACCESS.pdf

13:00 → 15:50 Poster session

13:00 Optical anisotropy of the ribbon skin-layer of Ni-based amorphous metallic alloys

Multicomponent amorphous metal alloys with ferromagnetic properties are a class of optoelectronic materials with unique set of optical, mag-netic and electrical properties. An important problem is the diagnostics of elastic-stress state of amorphous ribbons after their production by rapidly quenched method. In this paper to characterize the elastic-stress state of the $Ni_{78}Si_{8}B_{14}$ ribbons the parameters of electronic subsystem of alloy, namely plasma $\omega_{\rho}$ and relaxation $\gamma$ frequencies were used. These parameters were determined from azimuthal ellipsometric measurements by applying the functions $F_{1}-F_{3}$ that are based on the Drude ratio.
An ellipsometer in combination with a spectrometer ($\lambda=2-25\mu m$) was used to study the optical properties of $Ni_{78}Si_{8}B_{14}$ ribbons. As a result of the ellipsometric measurements we have obtained the spectral dependenes of the real $\epsilon_{1}$ and imaginary $\epsilon_{2}$ parts of the complex dielectric constant of the $Ni_{78}Si_{8}B_{14}$ ribbons at different values of the azi-muthal angle $\alpha$, latter determines the orientation of the longitudinal axis of the ribbon according to the incident light plane.
It was found that the plasma and relaxation frequencies of the amorphous $Ni_{78}Si_{8}B_{14}$ alloy are decreasing with the gradual azimuthal rotations of the ribbon in its own plane. This means that the number of free electrons becomes less with increasing mobility of charge carriers. Such behaviour of the electronic and optical properties of the skin-layer of the $Ni_{78}Si_{8}B_{14}$ ribbons is a consequence of presence of the deformations and elastic stresses that occur on both sides of the Ni-based alloy ribbon due to specific thermal conditions during its manufac-ture. It was found that formation of nanocrystals within subsurface layer of the ribbon makes an additional contribution to the revealed optical anisotropy of amorphous ribbon.

Key words: amorphous ribbons, ellipsometry, optical properties, electronic parameters

Speaker: Petro Kovanshi (Taras Shevchenko National University of Kyiv, Faculty of Physics, Chair of Optics)

13:05 Spontaneous and stimulated Raman scattering of lasing dyes in polymer matrices and molecule microcrystals (powders)

Raman spectroscopy is an important and informative source of information about dye molecules structure and its interaction with the matrix. However, very intensive luminescence of lasing strongly interferes detection of weak Raman scattering radiation. The use of conventional techniques of Raman spectra observation is restricted and complicated due to intense dye luminescence and wide absorption band. Thus development and investigation of alternative methods for Raman spectroscopy by using stimulated Raman possibilities is an actual problem.

This work is devoted to developing a new stimulated Raman spectra spectroscopy technique based on random lasing observation under strong light scattering (SRS-RL method) within the dye embedded in the vesicular polymer film. The observed structure was compared with dye Raman spectra in crystalline and polymer solutions forms obtained by conventional technique.

It was shown that Raman spectra observed by conventional technique reveal preferably the intense spectral lines of the polymeric matrix and substrate. Nevertheless, the SRS-RL method being inapplicable to dye powder investigating partially correlates with the dye powder conventional spectrum. Thus the comparison and analysis of both techniques spectra demonstrate that in contrast to conventional technique the SRS-RL method is applicable for Raman spectroscopy of organic dye solid solution.

Speaker: Ms Olha Pryhodiuk (Faculty of Physics of Taras Shevchenko National University of Kyiv)

13:06 Spectral properties of water-soluble melanines

Melanins are a class of organic compounds that act as pigments in living organisms. Melanins also play an important role in the human body. In particular, they protect tissues from the harmful effects of ultraviolet and other types of ionizing radiation as well as other aggressive carcinogens.
Melanins are pi-electron systems that absorb and emit light in the ultraviolet and visible spectral region. At the same time, the nature of absorption and emission centers in melanins has not been established so far.
The aim of the study was to investigate the spectral properties of water-soluble melanins of plant origin (isolated from black fungi collected in Antarctica and from black tea) to elucidate the nature of optical absorption and emission centers.
It was found that the optical density of aqueous solutions of melanin decreases monotonically with increasing wavelength.
The fluorescence and phosphorescence spectra of aqueous melanin solutions consist of several bands with different excitation spectra.
Low-temperature long-lived luminescence of melanins is characterized by large decay times (hundreds of milliseconds). The close position of the band peaks of low-temperature fluorescence and long-lived luminescence was also established.
The spectral range of absorption as well as the low intensity of fluorescence make melanins promising for their further studies as components of complex nanosystems for photoacoustics and photothermal therapy.

Speaker: Mrs Marharyta Morozova (Taras Shevchenko National University of Kyiv)

13:10 Realization of a device for detecting the electrical activity of the brain and the acquisition of the EEG electroencephalogram signal

The brain has always been the master of all human organs, being responsible for all voluntary or involuntary activities. For that, the brain is a subject of a many research such as neurobiology, neurology, psychiatry, psychology, linguistics, anthropology... Among the many methods of exploring the brain, the basic technique is EEG electroencephalography.

The electroencephalogram (EEG) is the recording of the electrical activity of the brain performed on the surface of the head through non-invasive or even invasive electrodes.

From where objective of our thematic is to realize a device that can detect the electrical activity of the brain for diagnostic purposes. Our work rallied two distinct steps, where the first is the electronic design of the EEG device including all its blocks starting with the sensor, a shaping circuit from which the acquisition as well as the recording of the EEG signal are assured by the Arduino card.

The second step consists of processing of the signals recorded on a Matlab programming environment for the purpose of diagnostic assistance.

Keywords: Electroencephalography, brain, EEG signal, arduino card, Matlab.

Speakers: Dr Lahouaria BADIR BENKRELIFA (University Center BELHADJ BOUCHAIB, Ain-Temouchent, Algeria; ), Dr Boumedyen BELAID (Abou-Bekr BELKAID University, Tlemcen, Algeria;)

13:14 Features of the RL radiation distribution in a limited random medium

The confinement of light in multiple scattering media (MSM) leads to the stimulated emission appearance, which called random lasing. Multiple scattering of light plays the role of nonresonant positive feedback which replaces the cavity mirrors in conventional laser. In real MSM having limited size, boundary reflection significantly affect the feedback.
In the presented work we held numeric modeling of RL with Monte Carlo method in dependence on MSM parameters: concentration of scattering particles, boundary reflectivity and sample's thickness. The active area in MSM was computed as result of absorption, scattering and boundary reflection of external pump the weight and direction of the photons of which change due to these effects. Preliminary the pump photon sequence (pulse) has been divided into separate packages which photon weights change due to these effects step-by-step between scattering acts or due to reflecting from the boundaries. The same computation was made for the package of RL photon which initial distribution in the MSM defined by calculated distribution of absorbed pumping.
The computation shows the RL photons' density in a MSM sample was distributed unevenly, forming a maximum. The boundaries reflectivity increases RL photon density with the sample thickness decreasing. By combining bulk scattering of a sample with a certain length and its boundaries reflection, one can achieve a significant RL energy without increasing the pump intensity. Experimental results confirm the simulation. Thus both effects substantially influence energy parameters of RL and are decisive for the selection of a sample suitable for a random laser.

Speaker: Mr Michael Zhuravsky (Taras Shevchenko National University of Kyiv)

13:18 THERMALLY STIMULATED CONDUCTIVITY AND LUMINESCENCE, PHOSPHORESCENCE AND CURRENT RELAXATION OF ZNSE MONOCRYSTALS AFTER X-RAY IRRADIATION

Zinc selenide (ZnSe) is one of the wide-gap АІІВVI materials and is widely used in semiconductor electronics. Specially undoped ZnSe single crystals can also be used as a semiconductor detector. In this regard, there is need for a complex study of electric and luminescent properties of ZnSe single crystals.
There was performed complex experimental research of X-ray conductivity (XRC), X-ray luminescence (XRL), thermally stimulated conductivity (TSC) and luminescence (TSL), phosphorescence (Ph) and current relaxation (CR) of ZnSe single crystals.
A comparison between the phosphorescence intensity and TSL intensities for both bands with maxima at 630 and 970 nm, and the comparison between current relaxation and the TSC current proved that they are the values of the same order. If we’d compare these values with the stationary values of XRL and XRC, we have that those relations are close for the 970 nm band and the current. And for the 630 nm band the relation of stationary X-ray luminescence intensity to the phosphorescence intensity or to the intensity of the first TSL peak is ten times higher than the corresponding ratio for the 970 nm band and for currents. This difference in the ratio of intensities and currents can be explained by the simultaneous implementation of these two mechanisms of recombination (electron and hole) on corresponding centers during X-ray excitation.
The bulk of generated free electrons and holes recombines at luminescence centers (94%) and only a small part (6%) goes to the charge accumulation during the X-ray excitation.

Speakers: Dr Volodymyr Degoda (Taras Shevchenko National University of Kyiv), Mrs Galyna Podust (Taras Shevchenko National University of Kyiv)

SPO2020.tif

13:22 Fluorescence-based temperature control applied to microwave heating: The role of spectral parameters

In this work, we used an aqueous solution of the thermosensitive dye rhodamine 6g for contactless control of heating in a microwave oven. Temperature dependence of spectral parameters in the range of 20-100 ° C, measured using a conventional contact heater. Relative intensity, peak wavelength, spectral bandwidth, and asymmetry coefficient exhibit approximately the same temperature sensitivity at the optimum dye concentration. The data obtained was used to monitor the temperature in real time during the rapid heating of the aqueous solution in the microwave. It is shown that the simultaneous control of several parameters can facilitate the identification of non-thermal effects of microwaves.

Speaker: Mrs Nataliia Haiduk

13:26 LUMINESCENT PROPERTIES OF THE La1-xSmxVO4:Ca NANOPARTICLES

The Eu3+-doped vanadate luminophores are widely used in optoelectronic devices for more than 50 years. At the last years, a great attention was also paid to investigation of vanadate matrices with other rare-earth luminescent activators, in particular - Sm3+ ions. In this paper we report results of synthesis and investigation of the Ca2+-doped La1-xSmxVO4 (0.05 ≤ x ≤ 0.2) nanoparticles synthesized by sol-gel method. The phase composition and crystal lattice parameters were controlled using XRD analysis. The obtained samples possess multiphase composition of mixed monoclinic and tetragonal structure. Content of the tetragonal LaVO4 phase is increased with increase of Sm3+ concentration.
Emission of the investigated samples is observed in the 550 – 725 nm spectral range and it shows narrow spectral lines. These lines can be assigned by their position to electron transitions in the Sm3+ ions. Excitation spectra consist of the broad band in 250 – 350 nm spectral range which caused by transitions in the VO43- groups and narrow bands in the 350 – 510 nm spectral ranges caused by the f-f transitions in the Sm3+ ions. It was found that changes in crystal phases influence fine structure of the emission and excitation spectra of the La1-xSmxVO4:Ca nanoparticles, whereas Ca-doping leads to formation of additional Ca-induced centers of luminescence excitation.
This work has received funding from Ministry of Education and Science of Ukraine under bilateral grant agreement No43-2020 and from the EU-H2020 program under grant agreement No654360 having benefited from the access provided by the NFFA-Europe Transnational Access Activity.

Speaker: A. Dorofieieva (Taras Shevchenko National University of Kyiv)

13:30 Modern state of optical microscopy

The paper analyzes the modern widespread microscopy techniques as wide-field, laser scanning confocal and structured illumination microscopy.
Wide-field microscopy is a technique, which provides fast imaging capture because all the field of view is illuminated uniformly. However, this technique has limitation in capturing 3D images using the software for digital focus extension. It also requires powerful light sources that can damage biological specimens.
Laser scanning confocal microscopy (LSCM) still remains the best choice due to the high lateral and axial spatial resolution. The modern LSCM allows observation with white light illumination, registration of 3D images in several spectral ranges and with multi-channel photodetectors. The principal limitation factor of LSCM is a high price – the typical models cost from 100K up to 2000K Euros. Some models with low resolution have price in range 50K– 80K Euros.
Structured illumination microscopy (SIM) can be considered as an economical alternative of LSCM. It allows capturing color 3D digital images with high axial and lateral spatial resolution. The principal advantages is possibility to update wide-field microscope with a motorized focus driver by a SIM slider. As a result, the price of a microscope for capturing 3D images becomes smaller 40K – 50K Euros. The other advantages is ability to create 2D and 3D periodical or stochastic patterns of structural illumination to reach the 2-folds superresolution in 2D and 3D spaces. The disadvantages of SIM are image distortions caused by formation or projection of 2D and 3D periodical or stochastic patterns in object spaces. It requires special image processing for restoration of images with the patterns on them.
Summarizing said above we conclude that SIM, in particular – updating the existing optical microscopes with economical SIM sliders, has good perspectives for Ukrainian laboratories. Such SIM makes possible 3D image capturing without spending big money for purchasing LSCM instruments.

Key words: wide-field microscopy, laser scanning confocal microscopy, structured illumination microscopy, spatial resolution

References:
1. Prof. Colin JR Sheppard. Confocal Microscopy // Imaging & Microscopy. – 2009-11-03.
2. Barry R. Masters. Confocal Microscopy and Multiphoton Excitation Microscopy: The Genesis of Live Cell Imaging. – SPIE Press, 2006-01-01. – 234.
3. Jan Huisken, Didier Y.R. Stainer. Selective illumination microscopy techniques in developmental biology // Development 136. – 2009. – 1963-65.
4. Cheng, Li-Chung; Chang, Chia-Yuan; Lin, Chun-Yu; Cho, Keng-Chi; Yen, Wei-Chung; Chang, Nan-Shan; Xu, Chris; Dong, Chen Yuan; Chen, Shean-Jen. Spatiotemporal focusing-based widefield multiphoton microscopy for fast optical sectioning // Optics Express. 20 (8). – 2012-04-09. – 8939–48.
5. Structured Illumination Microscopy | 3D SIM Imaging: https://andor.oxinst.com/learning/view/article/super-resolution-imaging-structured-illumination-microscopy

Speaker: Mr Oleksii Hudz (NTUU "Igor Sikorsky KPI")

13:34 Wavelength Dependence of Femtosecond Laser-Induced Periodic Surface Structures formed on Tungsten and Copper Surfaces

The report deals with the dependence of the period of the laser-induced periodic surface structures (LIPSS) on wavelength of incident laser radiation with the aim to make another step in the elucidation of the nature of LIPSS formation. The dependence of the LIPSS period on the wavelength of laser radiation could reflect the dispersion dependence of surface plasmon polaritons (SPPs) that take part in the interference of the incident light with surface scattered waves in the most accepted model of LIPSS formation. LIPSS on copper and tungsten have been obtained under an irradiation of linearly polarized Ti:sapphire femtosecond laser of fundamental (800 nm), second (400 nm) and third (266 nm) harmonics in air environment. The morphology of the sample surfaces has been analysed using scanning electron microscopy. It has been discovered some surface peculiarities. In particular, we partly obtained the structure that resembled spikes but not LIPSS at Cu surface under third harmonic of femtosecond laser. The preliminary obtained experimental data for tungsten in the spectral range from 266 nm to 800 nm demonstrate linear dependence of SPPs dispersion that represents the initial part of the theoretical dependence for SPPs in the range of values of k from 0 to 0.5 (in relative units). Another feature of the experimentally obtained linear dispersion law is the non-passage of the extrapolated line through the origin of coordinates. In particular, this indicates the existence of additional peculiarities (for instance, oxide films, surface tension) of the formed LIPSS on the metal surface.

Speaker: Mr Yevheh Hrabovskyi (Taras Shevchenko National University of Kyiv)

13:38 Specificities of anelastic characteristics of nano composites multiwalled carbon nanotubes and polyvinyl chloride, polyethylene, foam polystyrene

The influencing of ultrasonic (US) deformation εUS was researched on anelastic and elastic characteristics of nano composites of multiwalled carbon nanotubes (MWCNT).
It’s showed, that anelastic internal friction (IF) Q-1 and elastic modulus Е characteristics are essentially depended from morphology of surface layer [1]. The complex elastic modulus of polyvinyl chloride (C2H3Cl)n, polyethylene (C2H4)n, expanded polystyrene C8H8 nano composite Е is equal to the sum of dynamical elastic modulus E’ = ρV2║ and loss modulus E” = E’δ:
E = E’ + E” = E’ (1 + δ) = ρV2║ (1 + δ) = ρV2║ (1 + πQ-1) = ρV2║ (1 + αV/f), (1)
where δ – ultrasound (US) attenuation logarithmic decrement, ρ - specimen density; V║ - quasitransversal US elastic waves velocity, Q-1 – internal friction.
E”/E’ = δ = πQ-1 = αλ = αV/f, (2)
where α – US attenuation coefficient, λ – the US wave length, f – US frequency. The US attenuation logarithmic decrement δ vibrations with amplitude A = A0e-δx is equal to:
δ = ln(An+1/An) (3)
The increase of the nano composite crystalline degree at growth of multiwalled carbon nanotubes concentration filling with the nanotubes of matrix results in the decline of content of well-organized phase.
As the result of the mechanical study the presence of the strong effect between low-density polyethylene (C2H4)n, polyvinyl chloride (C2H3Cl)n and multiwalled carbon nanotubes was confirmed.
REFERENCES
[1] A.P. Onanko, D.V. Charnyi, Y.A. Onanko, M.P. Kulish etc. Conference Proceedings of 19 Geoinformatics: Theoretical and Applied Aspects, 2020, 1-5, (2020). DOI:
https://doi.org/10.3997/2214-4609.2020geo040.

Speaker: Lada Denis (Taras Shevchenko National University of Kyiv)

13:42 Trion formation and exciton photoluminescence enhancement in 2D MoS2 coupled with plasmonic metal nanoparticles

MoS2 emerged as promising candidate for photovoltaic, light emitting, optoelectronics and sensing applications. However, photoluminescence (PL) of 2D materials is still limited that motivates the researchers to explore the ways to enhance it. Plasmonic enhancement is one of best way to improve the PL in which, nanoparticles resonate with the free electrons present on the surface of 2D material. In this work, we report the PL enhancement of few layer MoS2 decorated with Ag nanoprisms by drop casting. Ag nanoprisms exhibit strong electromagnetic filed near the sharp edges or tips. The strong plasmonic field intensify the electric fields of exciting and emitting photons due to their coupling with surface plasmon resonance in Ag nanoprisms, that increases the photon absorption, radiative emission rate and quantum yield. The µ-PL spectra of MoS2 have two broad bands associated to A (~1.82 nm) and B excitons (~1.9 nm) at room temperature. The A exciton peaks becomes more broaden having a prominent shoulder after decorating MoS2 with Ag nanoprisms. The deconvolution proves that there is an emergence of A– trion component. In the vicinity of Ag nanoprisms, excitation of surface plasmons leads to the generation of hot electrons and transfer rate of hot electron from Ag to MoS2 increases due to their different work function that causes the generation of intralayer trion. This is a notable feature in our study that intralayer trion contribute highly in PL emission. So, the average PL enhancement is about 1.3 times. This work gives the new insight for future generation optoelectronic and nanophotonic devices.

Speaker: Ms Iqra Irfan (Shenzhen University)

13:46 CLASSIFICATION OF A NEURON

There are already several classifications for neuron modeling. Namely, classified by successor features [1]:
- By form of information presentation (digital or analog);
- Type of element base (electronic, hybrid and opto-electron);
- - the nature of the setting of synapses (constant or variable);
- Signal transmission time (synchronous or asynchronous);
- By the nature of the adjustment of synapses (fixed or infused weights);
Among the optoelectronic element base can be divided into the following groups:
- Based on photodiodes and operational amplifiers;
- Based on managed banners;
- Based on optical bistable SEED-devices;
- Based on space-time modulators;An example of a digital one-bit model is the model of a formal neuron [2]. The model is based on the usual R-S trigger. I-No logic elements, transistors, and sometimes an ionotron transistor are also used. This model is very simplified because the input and output signals are binary.
More complex and promising are digital multi-bit neuron modeling devices (PMN) [3]. The advantage of this method is the high accuracy of modeling, but at the expense of high hardware costs.
In analog PMN information is presented as a voltage level. Such a representative is a device for reproducing the transfer function of a nerve cell. The main element [4] is an operational amplifier, because of this they have less accuracy, but are hardware simpler than multi-bit digital. Despite this, it is impossible to build large-scale neural networks at the expense of analog PMN.
The most common are PMN with frequency-pulse form of information presentation. Since, like biological neurons, information is represented by impulses, and the level of excitation is determined by the frequency. They are classified by hardware complexity into the following groups:
- The most complex - uses a digital element base (counter, triggers, etc.)
- Medium complexity - analog element base is used (operational amplifiers, comparators, etc.)
- The simplest - nonlinear electronic or optoelectronic elements are used (single transistor [5], avalanche transistor [6], thyristor [7], bispin device [8], Schmidt trigger on MOS transistors [9]).
The disadvantages of this class of devices are the use of electrical inputs and outputs and low load capacity.
There is also a more advanced scheme of a pulsed neural network [10] using an optoelectronic element base. The advantage is that the optical signal is used to organize connections between signals, which can be located in three dimensions and work simultaneously. And also with the help of hardware without computational procedures, training and retraining are possible.
The disadvantage of this system is the presence of optical elements that significantly increase the weight of the device. And the presence of cylindrical lenses increases the volume and requires a powerful source of radiation (laser).
Several requirements must be considered when developing a pulse model of a neuron:
1) Must be functionally adequate to the biological neuron:
2) Have optical inputs and outputs in the case of using optical nodes;
3) It is advisable to use electrical capacity to integrate signals into the neuron;
4) It is necessary to use a threshold device
5) There must be a circuit of the integrator (capacitance) to generate the input pulse.
A more generalized classification of INS divides them into two classes depending on the availability of feedback. In the absence of feedback, it is called static, and in its presence - dynamic (recurrent).
Another principle of classification is based on technology [11]:
- - fully connected: - each neuron transmits an output signal to other neurons and to itself. An example is the Hopfield network;
- - Multilayered - neurons are grouped into layers. The layer has neurons with one input signal;
- - unconnected - nerons are located in rectangular nodes or hexal lattice. Each neuron is connected to several neighbors;
- - Modular (nuclear) - belong to the class of direct distribution. Each neuron of the next layer receives a signal from part of the neurons of the previous one. Thus, neurons of the nucleus are formed. inputs and outputs simultaneously. Each neuron is connected by synapses to other neurons and has its own synapse for signal input. Output signals are formed on axons.

Speaker: Ms Ira Avdeionok

13:50 MODERN UNLANDED AIRCRAFT LANDING SYSTEMS

The rapid development and spread of the use of UAVs in many spheres of public life, actualizes the development of methods of modern UAV landing systems, as landing is the most difficult stage of flight. Experts predict that the number of UAVs by 2020 will reach a fantastic number - 2.7 million [1]. This requires the creation of a large number of compact "airfields" for UAVs with equipment that ensures safe departure and landing even in difficult weather conditions. The use of GPS to ensure take-off and landing does not provide the necessary accuracy to determine the coordinates relative to the "aerodrome". Because most UAV sizes are 1 - 2 meters, and GPS-navigation of multicopters provides positioning accuracy of 10 - 15 meters [2], which is not enough for safe departure and landing. Therefore, these departure and landing operations are carried out under the control of the human operator, and this significantly increases the cost of transportation and does not eliminate operator errors.
Departure security and automation will lead to less stressful work for operators, who will now only be supervisors, and many carrier companies will be able to obtain permits to transport goods using UAVs (danger of landing and delivery are the most common reasons for failure to transport goods in some countries).
Now there are known many systems that can help UAVs automatically landing or taking off:
1. Systems that use cameras. The main principle is to obtain an image with further processing. The software then sets the position of the UAV relative to the landing site. Such systems can be of two types: those that use UAV cameras and those that use ground cameras and transmit a location signal to the UAV. The first must have a certain test object at the landing site (this may be a drawing, a set of light beacons, etc.). With the help of such test objects, you can find out the flight altitude, landing angle, position relative to the landing site and many other necessary information. [3] In the second type of camera systems, such a test object is the UAV itself. [4]
Camera systems are usually based on computer training, which complicates their development, and therefore, these systems can give some errors. The main disadvantages are the high price, the complexity of the system and the large weight.
2. Another type of landing system does not use a camera. Each of these systems has a different principle of operation. For example, the system described in [5] has two components. The first unit is located on the landing platform and initializes the signal in the form of a so-called "rainbow" in the IR range. The second unit is located in the plane or object we are landing, and consists of a spectrometer, and then the signal goes to the control unit. This system is accurate, can measure range, and is safe for pilots. This makes it possible to use it for both UAVs and manned aircraft. But the price and dimensions of such systems will be large.
The idea of the proposed system is based on the creation of a predetermined number of encoded rays of optical radiation in space, with which the object can determine its position in space relative to the illuminated parts. The solution to this problem is achieved by using modulated radiation sources as transmitters of certain codes to a certain area of space with a frequency equal to or approximately equal to the frequency of the receiver. The proposed method of positioning requires an optoelectronic system, which consists of two parts: radiating and receiving. The radiating part consists of a control unit for optical radiation source units, optical radiation source units with optical systems and a power supply unit. The receiving part consists of photodetector units with optical systems, a unit for calculating the position and a power supply unit. [6]
The technical result is the creation of a compact and economical optoelectronic system for landing UAVs using coded rays of optical radiation in space.
As you can see, there are many positioning systems in the world. Most of them are systems that use cameras. Although such systems have high accuracy, their use is sometimes more expensive than the machine they control, and these systems are large and difficult to create. Other systems do not use cameras, they are in most cases also accurate, but dimensional. The price for these systems is lower than the previous ones, but still high.
The proposed method has high accuracy, small size and low cost, easy to design and operate, so this device has all the prospects for further development and improvement.

[1] J. Goldman, "7 Reasons Why Drones are the Future of Business," 2018. [Online]. Available: https://www.inc.com/jeremy-goldman/7-reasons-why-drones-are-future-of-business.html.
[2] "33 Eye-Opening Stats About Drones for 2019," 12 March 2019. [Online]. Available: https://www.phillybyair.com/blog/drone-stats/.
[3] Marcin Skoczylas, "Autonomic drone landing system based on LEDs pattern and visual markers recognition," SPIE Digital Library, 1 October 2018.
[4] Paulson, "Infrared Landing System For A Mini Remotely-Piloted Vehicle," SPIEDigitalLibrary.org/conference-proceedings-of-spie, 20 November 2019.
[5] Starodubov, "Ship-relative instant multispectral position system," SPIE Digital Library, 4 May 2018.
[6] Боровицький В., Аверін Д. «Оптико-електронна система позиціонування», патент України на корисну модель, номер заявки No u2019 07320 (2020).

Speaker: Mr Dmytro Averin

13:54 Channels of Cs-137 and K transfer from soil to plant under natural conditions in the 10-km Exclusion Zone of the Chornobyl nuclear power plant

The mechanisms of potassium (K) and cesium (Cs-137) uptake by plants were studied using radish as an example. The investigations were performed at four experimental field sites within the 10 km Zone of the Chornobyl Nuclear Power Plant in 2012 and 2013:
Radish seeds were sown, and plants and their corresponding soil solutions were sampled, several times during each growing season. The concentration of Cs-137 in the samples was determined by a gamma-spectrometer with the semiconduc-tor detector HPGe ORTEC GMX40P4-83-RB POPTOP sn.48-TN22465A. Potas-sium concentrations at the samples of soil solutions and dissolved plants were measured by an optical method by atomic-absorbing spectrometer
С-115-М1.
It was observed that potassium and cesium entered plant roots, as a rule, through a complement of transporters with low selectivity when the concentration of dis-solved potassium (CK) in the soil solution was greater than 2 to 4 mkg/cm3. In this case the value of r was near 1. However, when CK was between 0.5 and 2 to 4 mkg/cm3, potassium also appeared to enter plant roots through highly-selective potassium transporters, whilst cesium entered roots only through the transporters with low selectivity. In this case the value of r was much less than 1. When CK was less than 0.5 mkg/cm3, cesium appeared to enter roots through a comple-ment of transporters with greater selectivity for cesium than potassium. The value of r in this case could exceed 1.

Speaker: Mrs Olga Prigodjuk (Taras Shevchenko National University of Kyiv)

13:58 Study and conception of a device dedicated to wireless neuromuscular stimulation

These last decades the world has known a major development in the medical sector in general and in the well-being of personnel in particular, where the appearance of neuromuscular stimulators have responded to the various treatment of therapy.

A large number of dysfunctions within the nervous system cannot be resolved by conventional classic therapeutic without side effects. To resolve this problem, a Neuromuscular Stimulator technology is used, where the applications of electrical stimulation are several.

In this work, we present a neuromuscular stimulator dedicated to the realization of two main functions: an analgesic function which makes it possible to numb a part of the body and another which provides muscle massages and other functions such as: capillarization and aesthetics.
The electrical impulses generated by this device are transmitted by electrodes placed on the part of the skin to be treated. Its working principle is helping the brain to produce a higher rate of a substance called beta-endorphin, and this by generating very specific frequencies, which have been delivered through the Arduino Uno card, which made our task faster and more efficient.
Physiotherapy departments tend to use neuromuscular stimulators, but the need for an effective device is highly valued by users.

Speaker: Dr Lahouaria BADIR BENKRELIFA1 (BELHADJ BOUCHAIB University Center)

14:02 Eccentric fiber Bragg grating for refractometry

In-fiber grating-based sensors have many advantages over conventional electric and alternative fiber optic sensor configurations. We proposed and fabricated an Eccentric Fiber Bragg Grating (EFBG) inscribed by Point-by-Point (PbP) in conventional single- mode fiber (Corning SMF-28) using an IR femtosecond laser. Potential applications of eccentric FBG in refractometry, sensing are further illustrated.

Speaker: Dr Hicham Chikh-Bled (University of Tlemcen)

14:06 ELLIPSOMETRY OF CUSCN/STILBAZOLIUM DYE HYBRID THIN FILMS

Hybrid organic-inorganic films are a promising material for use in dye-sensitized solar cells. The purpose of investigation was to study the optical properties of hybrid organic-inorganic films of CuSCN copper thiocyanate with stilbazolium dye of different concentration.
As a method of research the multiple-angle-of-incidence ellipsometry implemented in the device LEF-3M-1 with a wavelength of light incidence nm was used. The ellipsometric parameters of the samples such as a phase shift between the orthohonal components of polarization vector and an azimuth of the restored linear polarization were measured. To characterize the optical anisotropy of samples of CuSCN/stilbazolium dye films azimuthal measurements of the ellipsometric parameters were performed when the studied samples rotated in their own plane. The effective refractive and absorption indices as well as the optical conductivity for the samples were determined from the data of the ellipsometric measurements.
It was found that the first increase of the concentration of the dye in hybrid organic-inorganic films leads to the increase in both the refractive index and the optical conductivity. However, for the films with maximum dye concentration of 1000 μmol/dm$^3$ the optical conductivity decreases significantly. The behavior of ellipsometric parameters for this sample is significantly different from the behavior of ellipsometric parameters for samples with dye concentrations of 25 and 250 μmol/dm$^3$ namely it is similar to the ideal dielectric. Such behavior of the optical properties of the films is explained by structural phase transition in CuSCN at certain dye concentrations. It was found that investigated samples are optically isotropic.

Speaker: Kononenko V.M. (1Taras Shevchenko National University of Kyiv, Faculty of Physics, Chair of Optics)

14:10 variation of chromatic dispersion in optical fibers

The optical fiber is the privileged channel of transmission for broad-band communications. To respond to increasing needs, it is essential to improve the characteristics of optical fibers, primarily those relating to the chromatic dispersion. This negative phenomenon limits the transmission rates. This has the effect to canceling the chromatic dispersion only for the wavelengths above than 1270 nm.
In this paper, we are interested in applications of new generation of optical fiber (FMAS) dedicate to the optical telecommunication such as the chromatic dis-persion.
Our studies concern the optimization of the parameters in FMAS to modeling the chromatic dispcersion by the Beam Propagation Method (BPM).

Speaker: Dr Mohammed DEBBAL (University Center BELHADJ BOUCHAIB)

DEBBAL Mohammed_Poster.docx

14:14 Corderoite-type nanomaterials for optoelectronic applications

The remarkable progress was achieved in the study of the physical and chemical properties of Hg3X2Y2 (X= S, Se, Te; Y= F, Cl, Br, I) crystals. Their optical properties such as high refractive index, photoconductivity, electrooptical effect, optical activity, optical nonlinearity etc., make them promising nanomaterials for nonlinear application. From the structural point of view, the corderoite family crystals are well ordered, and observed that the basic structural unit is a [XHg3] pyramid. The crystal structure consists of two sets of octahedral spirals with different radii and twisting directions. These crystals possess an excellent transparency in the mid-IR spectral range. Due to these features, the mentioned crystals in nanoparticle form have a wide range of optical applications in nanophysics. Obtained data suggest that the optical properties of the titled crystals should be taken into account in the studies concerning optical diagnostic methods in medicine. At the same time due to the transparency of corderoite family compounds in the wide region of the visible and IR-range (from 0.3 to 40 mcm) creates new opportunities for materials design. They have a great potential for wide range of possible application in optical devices: elements for dynamic holography, recording and information storage, modulators, deflectors and other devices based on the phenomenon of the interaction of light beams.

Speaker: Dr O.V. Bokotey (Faculty of Physics, Uzhhorod National University)

14:18 Optical features of semiconducting crystal Hg3S2Br2: first-principles investigation

First-principles calculations based on the density functional theory (DFT) were carried out to investigate the electronic and optical properties of semiconducting crystal Hg3S2Br2. The electron exchange-correlation energy was described by the generalized gradient approximation (GGA) and modified Becke-Johnson (MBJ) potential. The analysis of the band energy dispersion shows that the optical band gap is estimated to be roundly 2.69 eV. It is in satisfactory agreement with experimental value of 2.9 eV. The band topology near the conduction band minimum is changed due to the spin-orbit coupling in the mercury orbitals at the Г-point of the Brillouin zone. The essential contribution into the energy of the Hg-S bond adds the hybridization of sulfur p orbitals that are oriented along the bond. However, some contribution to the bond between the [SHg3] trigonal pyramids of the [Hg3S2Br4] octahedra also came from hybridization of p orbitals of sulfur atoms that form neighbor pyramids. Using the calculated dispersion of the real and the imaginary parts of the complex dielectric function, one can determine other optical properties such as absorption coefficient α(ω), refractive index n(ω), extinction coefficient k(ω), energy loss function L(ω) and reflectivity R(ω). The first crucial point of the optical absorption edge emerges in the visible light (at about 5 eV) and, with enhancing photon energies, the region with high absorption expands up to the 33 eV revealing the formation of some spectral features emerging due to different optical transitions.

Speaker: Dr O.V. Bokotey (Faculty of Physics, Uzhhorod National University)

14:22 Stepwise behavior of surface properties in the filled polymer blend

Polymer blends are widely used to obtain materials with improved characteristics. Interfacial tension (or surface energy) is one of the key parameters that determine the level of adhesion between the components of a polymer blend.
The composite under study is based on the polymer blend of PP/CPA and filled with Fe, which is localized only in the CPA phase. The study showed that concentration dependence of the free surface energy (FSE), like its dispersive and polar components, has stepwise behavior. The biggest changes of investigated characteristics are occurring in the phase inverse region (7-18 vol.% of Fe), where both phases PP and CPA-Fe are co-continuous. In this region, there is a sharp change in surface energy and its polar and dispersive components due to the rapid redistribution of the polymer phases of PP and CPA-Fe, both in volume and on the surface of the composite. In concentration intervals outside the region of phase inversion, the change in the values of FSE and its components is insignificant. Throughout the phase inverse region in the composite, there is a redistribution of the values of the polar and dispersion components in the total value of the surface energy. The relative contribution of the polar part increases from 1% to 14%, while the relative contribution of the dispersion part decreases from 99% to 86% in the evolution of composite morphology from the structure of PP-matrix with inclusions of CPA-Fe phase to a structure where the matrix is CPA-Fe with inclusions of the PP phase.

Speaker: Mr Andrii Misiura (Taras Shevchenko National University of Kyiv, Faculty of Physics)

14:26 Electroluminescence degradation of UV LEDs 365 - 405 nm at long-term operation

Ultraviolet (UV) light emitting diodes (LEDs) are gradually displac-ing gas-discharge UV sources due to advantages: greater energy effi-ciency, increased reliability, ease of wavelength and intensity changes, narrow spectral range, light weight and compactness. Application of UV LEDs are very diverse, in particular, are relevant applications where high power UV radiation is required - polymerization and curing of materials, disinfected and more. But a significant problem of UV LEDs 365 - 405 nm, is overheating and, accordingly, the rapid degradation of individual chip in LEDs matrices. This primarily applies to LEDs with wavelengths λ = 365 nm [1].
The degradation and thermal characteristics of industrial UV LEDs InGaN/AlGaN/GaN, the maximum wavelength of radiation λ = 365… 405 nm are studied. Rated current 350 mA, electric power 1… 1.4 W, area of the structure 1 mm2. The dependences of radiation intensity on time (degradation curves) at continuous operation for ten UV LEDs with dif-ferent wavelengths for 1 year at a nominal direct current of 350 mA are obtained. It was found that during the year the largest decrease in elec-troluminescence intensity occurred in LED 365 nm, less - 375 nm, and even less - 385 nm. The intensity of 395 nm LED increased slightly, and for 405 nm SD remained unchanged.
REFERENCES
[1] V.P. Veleschuk, A.I. Vlasenko, Z.K. Vlasenko, I.V. Petrenko etc. Optica Applicata 49 (1) 2019, p. 125 – 133

Speakers: Mr Vitaliy Veleschuk (V.E. Lashkaryov Institute of Semiconductor Physics, NASU), Mr Yevgen Malyi (Institute for Nuclear Research, NASU)

14:30 New KuQuinone for solar cells applications

We have investigated the structural, morphological and optical properties of dibenzofluorene derivative, which is part of the new sub-class of dibenzofluorenes, due to its existence as a zwitterion, in contrast to other KuQuinones. Microstructural and morphological characterization data, as well as powder X-ray diffraction study, confirm the amorphism of dibenzofluorene derivative in the present form. The Eg value calculated from the absorption and transmission spectra of thin films indicates the ease of the electrons transporting from the HOMO level to the LUMO level during light absorption. The optimization of the dibenzofluorene derivative was performed using density functional theory (DFT) by the M06-2X/cc-pVTZ + PCM (CH3CN) method. The UV spectra were calculated using CAM-B3LYP/cc-pVTZ and W97X/cc-pVTZ + PCM (CH3CN) methods. Our theoretical results confirm and explain the obtained experimental data. As a result, this material is expected to be applied as a light harvester thin-film and an optoelectronic design for further applications.

Speaker: Oleksandra Bugera (Department of Organic Chemistry, Faculty of Chemistry, Taras Shevchenko National University of Kyiv)

14:34 Vibrational properties of amorphous As-S-Ge glasses studied by Raman spectroscopy

Amorphous chalcogenides have received much attention in recent years, due to their unique properties and versatile technological applications such as infrared optical elements, acousto-optic and all-optical switching devices, holography recording media etc.
The aim of this study is to carry out the detailed study of vibrational properties of the pseudo-binary (As₂S₃)_x(GeS₂)_1-x chalcogenide system (x = 0.0, 0.1, 0.2, 0.4, 0.6, 0.8, 1.0) as a function of composition x with high-resolution Raman spectroscopy. The polarized-VV, depolarized-VH and depolarization ratio Raman spectra for the investigated glasses were obtained.
Raman spectra were analyzed and fitted using series of Gaussians peaks. The observed bands can be explained by vibrational modes of As₂S₃ and GeS₂ glasses. At least eleven vibrational modes are detected in the Raman spectra at 20-25, 110, 190, 205, 237, 260, 320, 342, 370, 430 and 490 cm^-1. Raman spectra of (As₂S₃)_x(GeS₂)_1-x samples showed that the backbones of the studied samples consist of AsS_3/2 pyramidal units, edge- and corner-shared GeS₄ tetrahedral units. Compositional dependencies of the Raman bands in studied glasses are observed.
The highest values of the depolarization ratio, practically independent on composition are detected in the low-frequency Raman spectra region. The lowest values of the depolarization ratio are found to be composition dependent with numerical maximum or minimum in the height for the alloy with x = 0.4.
Thus, Raman data show that (As₂S₃)_x(GeS₂)_1-x chalcogenide glasses contain different nanophases whose concentration is changing along chosen compositional cross-section.

Speaker: L. Revutska (National Technical University of Ukraine “Igor Sikorsky Kyiv Polytechnic Institute”)

14:38 High-performance 3D X-ray microtomography for non-destructive testing of materials and products in microelectronics

3D X-ray microtomography (3D X-ray micro-CT) is a method of non-destructive layer-by-layer examination of the internal structure of an object. The method is based on measuring the attenuation of X-ray radiation depending on the density of the material that absorbs it. The object is scanned at different angles and by measuring the intensity of the absorbed X-ray radiation.

Various operating principles of microCT allow you to examine both biological and industrial materials, goods of micro- and nanoelectronics, without distortion. The 3D scanning allows to visualize the surface und internal microstructure of goods, which is effective for further analysis.

A pioneer in compact X-ray micro-CT production is the company Bruker Corp. (USA). Bruker's portfolio of X-ray micro-CTs offers non-destructive 3D imaging solutions for a wide range of industrial and scientific applications. New SKYSCAN 1273 is high performance 3D X-ray micro-CT and one of the latest developments from Bruker Corp. The main features of SKYSCAN 1273 are:
- size of samples up to 500 mm in length, 300 mm in diameter and a maximum weight of 20 kg
- 0-130 kV X-ray source
- 8 position automatic filter changer for automatic energy selection
- GPU accelerated for fast 3D reconstruction
- truncated scanning with automatic stitching of large images

The integrated 3D.SUITE software allows you to reconstruct images and display the reconstructed results as layer-by-layer films or three orthogonal projections. The method of 3D X-ray microtomography is highly recommended for inspection of materials and good od micro- and nanoelectronics.

Speaker: Dr Olena Vertsanova (National Technical University of Ukraine “KPI”)

14:42 A robust ratio for light ellipticity in magneto-optical Kerr effect

In this paper we developed a unified equations describing ellipticity of reflected light as a function of off-diagonal dielectric tensor components in magneto-optical Kerr effect. The approach allowed us unifying numerous published results which introduced equations for experimental data analysis having different signs and absence/presence of imaginary unit at complex refractive index. The experimental dependences of the off-diagonal components of the optical conductivity tensor in the spectral region 1.25-5.06 eV were theoretically analyzed for alloys on the basis of cobalt, iron, and boron also applying different equations from the literature. Depending on positive or negative imaginary part of the complex refractive index and the Kerr angle taken in the equations, the resulted non-diagonal components of the optical conductivity tensor dispersion dependences had divergent character. Also the classical free electrons theory of metals also has been applied to evaluate typical numbers of off-diagonal tensor elements which appeared to be a few order magnitudes less comparing to dielectric tensor eigenvalues.

Speaker: Dr S. Rozouvan (Taras Shevchenko National University of Kyiv, Faculty of Physics, 64/13 Volodymyrska str., 01601 Kyiv, Ukraine)

14:46 Selection rules in magneto-optics for cobalt-iron based nanocomposites

We developed a theoretical approach based on electron gas in a metal with angular momentum coupled to magnetic field in order to explain magneto-optical (MO) properties of ferromagnetic alloys. In frames of the model the magnetic quantum number and Hund’s rule can be applied for ascertaining the MO alloys properties. Hund’s rule directly influences the dielectric tensor off-diagonal elements signs. Selection rules for the magnetic quantum number were applied to explain spectral ellipsometry experimental data. of (Co41Fe39B20)x(SiO2)100−x alloys. The nonrelativistic Schrödinger equation for the Co2Fe2B alloy was numerically solved in frames of quantum mechanical molecular calculus by taking into account spins of Co and Fe atoms as well as orbital moments of wave functions. Applying the modified Spicer formula for optical conductivities for different spin directions, we can obtain optical tensor off-diagonal components which are responsible for MO Kerr effect. The measured dispersion curves of off-diagonal optical conductivity of the alloys demonstrate shift of the resonant frequency to higher energies depending of percentage of non-conducting SiO2 in the samples in good agreement with the developed theory.

Speaker: Dr S.G. Rozouvan (Taras Shevchenko National University of Kyiv, Faculty of Physics, 64/13 Volodymyrska str., 01601 Kyiv, Ukraine)

14:50 Spectroscopic study of water clusters in synthetic calcium hydroxyapatite

Synthetic calcium hydroxyapatite Ca10(PO4)6(OH)2 is very similar to the main mineral component of the hard tissues of living organisms. Thus, it is actively used in innovative medicine as a filler for artificial bones, for the manufacture of implants, in dentistry, etc. Mostly, such objects are in the aqueous environment, and small clusters of water have recently been discovered inside nanostructured calcium hydroxyapatite. Since the presence of water can significantly affect physical and chemical properties of minerals, information on the interaction of nanostructured calcium hydroxyapatite with water molecules can be useful from a practical point of view.
Three different samples of synthetic calcium hydroxyapatite were studied by means of vibrational spectroscopy. Raman and IR spectra of different samples were registered, as well as their SEM images. The conclusions about water content in each sample were made. Luminescence spectra of all three samples of calcium hydroxyapatite were studied under X-ray excitation at temperatures 295 K and 85 K. It was shown that at a low temperature (85 K), the luminescence spectra differed significantly from each other. This difference can be explained by their different structure and by different degrees of hydration of the samples.

Speaker: Dr Iryna Doroshenko (Taras Shevchenko National University of Kyiv)

14:54 ELEMENTAL COMPOSITION OF NANOSTRUCTURED SILICON

The search and synthesis of modern nanomaterials, as well as an in-depth study of their physical properties, is a priority scientific and technical task. The uniqueness of properties of nanoscale and nanostructured objects is largely determined by atomic and electronic processes that take place both in volume and on the surface and significantly depend on the influence of dimensional effects. One of the promising nanocrystalline materials is nanostructured silicon, the properties of which depend largely on the method and modes of formation. Since the properties of formed layers of nanostructured silicon during chemical etching depend on the etchant composition and etching time in the work was a detailed study of the elemental composition of nanostructured silicon layers formed on the surface of monocrystalline and textured silicon for solar cells by the method of Auger spectroscopy. Nanostructured silicon layers were obtained by stain etching (chemical etching) of initial and textured monocrystalline silicon. The surface morphology of nanostructured silicon was studied using a scanning electron microscope and a scanning tunneling microscope. It is shown that depending on the etchant composition and the concentration ratio of its components, there is a significant change in the elemental composition distribution of nanostructured silicon. The latter is crucial for optimizing the formation modes of nanostructured silicon layers with preset properties for use in solar cells, as a new type of silicon optoelectronic devices, the active element of biological and biochemical sensors.

Speaker: Mr Mykola Melnichenko (Taras Shevchenko National University of Kyiv)

14:58 Effect of a low-temperature Ar matrix on hydrogen-bonded clusters (H2O)n

Matrix isolation is one of the most effective methods to investigate individual molecules of small clusters by spectroscopic methods. Though the matrix material is inert, there is still an effect of low-temperature matrices on the structure and vibrational spectra of isolated molecules. The main purpose of this study is to investigate the argon matrix effect on the structure, dynamics, and infrared (IR) spectra of small water clusters (H$_2$O)$_n$ with n = 1 - 6. Quantum-chemical calculations of optimal structure and IR spectra of the mentioned clusters in a face-centered cubic (fcc) argon crystal fragment with 108 Ar atoms were made using Gaussian software. The calculations were carried out by the M06-2X method with CRENBL EC basic set for Ar atoms and aug-cc-pVD basic set for water molecules. The results of calculations were compared to the experimentally registered IR spectra of water clusters in an Ar matrix and the corresponding assignment of the spectral band was made.

Speaker: Mrs Antonina Vasylieva (Taras Shevchenko National University of Kyiv)

15:02 MORPHOLOGY OF NANOSIZED GOLD FILMS

Films with nanoscale thicknesses and nanoparticles are widely used in all areas of nanotechnology. Nanoparticles of gold are of great interest in physics, chemistry, biology, and medicine. Gold nanoparticles are non-toxic, chemically stable, and biocompatible with living tissue. Unlike bulk gold, nanostructures have unique properties - catalytic, ferromagnetic, and tunable optical properties. The presence of such specific properties is the basis for a more detailed study of nanoscale structures, their properties, and methods of production. In this work, nanoscale gold films on a dielectric substrate of mica and gold nanoparticles obtained by various spraying methods were studied by tunnel microscopy. A comparative analysis of the morphology of the formed nanoparticles on silicon and glass substrates was carried out. It is shown that despite the differences in morphology of thin gold films obtained by different methods and on different substrates, the films consist mainly of spherical nanoparticles. Thus, having the opportunity to compare data on the vacuum deposition mode, and surface relief, it is possible to develop technologies for obtaining a surface with a given set of properties, as well as to develop new methods of gold deposition on different surfaces. Obtained results are very important for the application in biology and medicine. They make it possible to create different types of sensors, diagnostic tests, as well as targeted delivery of medicines to treat diseases.

Speaker: Ms Daria Havryliuk (Taras Shevchenko National University of Kyiv)

15:06 RESEARCH OF THE ELECTRON STATE IN A PRISMATIC QUANTUM DOT WITH A SHELL

In the element base of modern information technologies (monitors, lasers, sensors) use quantum dots that have extremely small sizes. Therefore, the development of mathematical models of various quantum dots (spherical, cylindrical, prismatic, conical), which allow to determine the eigenvalues of energy, is an urgent task. The results of the study of the dependence of the shape and parameters on the energy spectrum of the electron state are used in the development of technologies for obtaining and applying quantum dots.
Mathematical computer modeling of the state of electrons at a prismatic shell quantum dot was considered. The Schrödinger wave equation for steady states and the corresponding boundary conditions are used to determine the wave numbers and eigenvalues of energy. The dependence of the type of electron density density in a given region on the parameters of a quantum point is investigated: a, H is the edge length, d is the shell thickness.
3D graphics are constructed using structured discrete grids. To solve the Schrödinger equation, we use the Fourier method of separation of variables, as well as the numerical method of successive approximations (iterations). The wave function must be continuous and smooth at the core-shell boundary. The results of calculations of natural energy for two states of an electron are presented: ground and excited in the case of even and odd wave functions for horizontal and vertical modes.
The results are compared with the case of a spherical quantum dot and experimental data.

Speaker: Mr Mykola Morozov (Dmytro Motornyi Tavria State Agrotechnological University)

poster Morozov Domina Khalanchuk.xps

15:10 OPTICAL PROPERTIES OF FILMS BASED ON MEROCYANINE DYES

Merocyanine dyes are donor-acceptor polimethine molecules with unique spectroscopic properties used for design of advanced photonic materials, solar cells ets. Merocyanines, with their wide absorption bands, are suitable applicants for this goal. Optical characteristics of such compounds are very sensitive to a type of solvent, molecular concentration due to that methods and conditions of films preparation should influence their spectra.
Quantum-chemical calculations of optimized molecular geometry for single molecules and their aggregates were performed using ab initio density functional theory method DFT/CAM-B3LYP//6-31G(d, p), transition characteristics were calculated using semi-empirical ZINDO method in Gaussian 09 program package.
Absorbance of films of merocyanine dyes prepared by spin coating on the films comparing to the spectra in solution undergoes to shift of absorption maximums towards red region and new wide maxima appear; absorption intensity of the main peak decreases.
The first one is caused by interaction of the considered molecules due to alternation of atomic charges on the molecular chromophores. As a result of that J- and T-type aggregates are formed, which is confirmed by quantum-chemical calculations. According to the obtained data T-aggregation prevails. Therefore, merocyanine dyes in films absorb more wide spectral region, that is useful for harvesting of solar energy in order to transform it into electricity power in solar elements of organic electronics.

Speaker: Prof. Mykola Kulish (Taras Shevchenko National University of Kyiv)

15:14 Synthesis and luminescence properties of K3Gd(PO4)2:Eu phosphor

Design of new compounds for application in optoelectronic devices is one of the most actively developing branches of material science. In particular, various simple and complex oxides actively studied as materials for display panels and white light emitting diodes (WLED). Phosphate compounds doped with rare-earth (RE) ions were found to be one of the most promising for WLED applications due to good stability on action of high light fluxes, temperature, humidity, etc. The RE ions can greatly improve optical characteristics of oxides but concentration quenching of photoluminescence (PL) usually occurs starting from some content of RE dopants in host materials. Thus, increasing of luminescence intensity cannot be achieved only by increasing of RE content. This problem can be partially solved through co-doping of host with two types of ions, one of them acting like sensitizer for another.
In this work the Gd3+ ions are considered to be sensitizers for highly luminescent Eu3+ ions in K3Gd(PO4)2 host. The series of the K3Gd1-xEux(PO4)2 samples (where x= 0.01, 0.03, 0.07 and 0.10) were synthesized by growth from melt and by solid state techniques. The samples were characterized by means of powder X-ray diffraction, IR and luminescence spectroscopy.
The samples retain crystal structure of K3Gd(PO4)2 within range of the Eu3+ concentrations studied. Orange-red luminescence of the samples related with emission transitions in Eu3+ ions only. Energy transfer from Gd3+ ions to Eu3+ ions was found from PL excitation spectra. The studied samples are perspective red phosphors for LED applications.

Speaker: Vitalii Chornii (1)National University of Life and Environmental Sciences of Ukraine; 2) Taras Shevchenko National University of Kyiv)

15:18 The Magnetoresistance of Single Wall Carbon Nanotubes Modified by Nickel

The work presents the results of magnetoresistivity investigations of modified with nickel single wall carbon nanotubes (SWCNTs) at T=293 K at different mutual orientations of the magnetic field and current through the specimen.
SWCNTs have been obtained by arc method with use Ni particles as catalysts. The specimen of CNTs contains SWCNTs with a diameter of 1.5 nm and nickel particles up to 2 nm.
The angle between the direction of the magnetic field and the cur-rent through the specimen was 00 (parallel orientation), 300, 600 and 900 (perpendicular orientation). The error in measuring of resistance did not ex-ceed 0.1%.
For all mutual orientation of magnetic field and current through specimen the magnetoresistance is positive and increases with increasing magnetic field.
In the field dependences of the magnetoresistance at mutual orientation 00, 300 and 600 there is no hysteresis, that is very often observed in the magnetoresistance for CNTs modified with magnetic metal. The hyste-resis is observed only at perpendicular orientation of magnetic field and cur-rent and the magnetoresistance in the field up to 2.2 T does not reach satura-tion.
The asymmetry of the magnetoresistance for bulk specimen of modi-fied by nickel SWCNTs is associated with significant heterogeneity of the specimen structure and the presence of nanosized nickel particles. Na-nosized nickel particles cause inhomogeneity of the Hall transverse voltage along the specimen.

Speaker: Денис Шпілька

SPO-2020.ppt

15:22 Specificities of adsorption properties of SiO2 + Si, nano composites of multiwalled carbon nanotubes and polyvinyl chloride, polyethylene, foam polystyrene after laser radiation

A non-destructive method for the technological control of the structure defects by measuring internal friction (IF) and E after laser radiation was developed. The study of influence of structure defects on damping of vibrations in Si + SiO2 plates by the diameter of D = 100÷60 mm and by the thickness of hSiO2 ≈ 600 nm, hSi ≈ 400 000 nm allows to estimate the degree of perfection of crystalline structure.
Effects of acoustic emission (AE) after nanosecond neodymium and ruby laser irradiation in fluid SiO2 are investigated. The fusion depth as the result of relaxation of photothermal elastic strains Ϭi at the large time ∂T/∂t = (55±100).109 K/sec and spatial ∂T/∂x = (1±2).104 K/sm temperature gradients on the SiO2 surface was appraised Δh ≈ 10000 nm [1]. The quantity of reflections N = τ/t ≈ 0.2 nsec/0.02 nsec = 10, approximately 10 times forward-back in specimen.
The crater fusion depth Δh at constant intensity I and laser irradiation time t is limited by the local heat-conducting and establishment of “time-equilibrium” distribution of temperature gradients ΔТ perpendicular to the crater axis and along it.
Outcomes of an evaluation of dynamic characteristics interstitial atoms Sij, vacancy V and O-complexes can be applied for account of a condition of an annealing with the purpose of deriving structural defects in SiO2 + Si after laser radiation.
REFERENCES
[1] A.P. Onanko, M.P. Kulish, Y.A. Onanko. Conference Proceedings of 2012 IEEE international conference on oxide materials for electronic engineering (OMEE), Lviv, Ukraine, 81-82 (2012). DOI: 10.1109/OMEE.2012.6464790.

Speaker: Bogdan GRYGORENKO (Taras Shevchenko National University of Kyiv)

15:26 Artificial compound eye

Simple structure of insect’s compound eye, gives to us an opportunity to build very efficient and cheap optoelectronic vision systems for orientation, navigation and preventing collisions between unmanned air vehicles. Nevertheless, there are only a few designs that implement the idea of facet vision systems:
First one is a system that has micro-lens array on a matrix of photodetectors [1]. It contains two main subsystems. The first one is an array of 16 x 16 convex microlenses with radius of curvature r ≈ 400 µm. The second subsystem enables photodetection and electrical readout. It consists an array of thin silicon radiation sensors and blocking diodes. Each photosensor placed in focal position of corresponding lens. Some interesting feature of this approach is possibility of elastic deformation of prototype assembly (dynamical FOV) that is a big advantage.
Another approach is the development of an artificial compound eye, called CurvACE [2]. As in the biological compound eye, CurvACE contains three material and functional layers. The first layer contain array of polymeric microlenses molded on a glass carrier, which focus light onto second layer that includes silicon-based photodetectors array. Last layer is a flexible electromechanical board that transmits output signals to processor units. The use of a single microprocessor in such a solution may not be sufficient since a high speed of signal processing from each photodetector is required.
An interesting research in [3] is based on vision principle of Xenos peckii eye. It’s a biologically-inspired ultrathin digital camera where the lens has two-layer structure: honeycomb-packed concave hexagonal microprism and microlens plates. They can be integrated together on conventional CMOS image sensor. After microassembly of the microprism and microlens plates, the device was fully integrated on a CMOS image sensor (2M pixels, unit pixel: 1.75 x 1.75 μm), and the total track length of the bioinspired ultrathin digital camera is 1.4 mm. Approach of microlens array placement on CMOS-sensor has a principal advantage: small size and weight of utilized elements. But the major drawback of such solution is a lack of multichannel sequential read-out efficiency that is very important in true parallel signal processing.
Said frankly all these designs are far from the principal idea of insect compond eye because they do not perform parallel image processing in the multiple independed facet elements. The proposed design of the compound eye with the multiples facet elements equipped with image processing units can be considered as the closest one to an insect’s compound eye then the above-mentioned ones [4].

References

[1] Y. M. Song, Y. Xie, V. Malyarchuk, J. Xiao, I. Jung, K.-J. Choi, Z. Liu, H. Park, C. Lu, R.-H. Kim, R. Li, K. B. Crozier, Y. Huang and J. A. Rogers, "Digital cameras with designs inspired by the arthropod eye," Nature, vol. 497, pp. 95-99, 2013.
[2] R. Leitel, A. Brückner, W. Buß, S. Viollet, R. Pericet-Camara, H. Mallot and A. Bräuer, "Curved artificial compound-eyes for autonomous navigation," Proceedings of SPIE, vol. 9130, p. 11, 2014.
[3] D. Keum, K.-W. Jang, D. S. Jeon, C. S. H. Hwang, E. K. Buschbeck, M. H. Kim and K.-H. Jeong, "Xenos peckii vision inspires an ultrathin digital camera," Light: Science & Applications, vol. 7, p. 80, 2018.
[4] https://sis.ukrpatent.org/uk/search/detail/1445349/

Speaker: Mr Vitalii Antonenko (NTUU "Igor Sikorsky KPI")

15:30 ESTIMATION OF TRANSMISSION QUALITY IN WDM NETWORKS

High speed data rate is a very imperative requirement today and it is increasing according to the customer requirements for various applications such as live broadcasting, video on internet, video conferencing etc. This research is based on how we can design and analysis the optical fiber communication system. . WDM with enormous bandwidth and low energy consumption has been considered to construct optical access network. In this paper, we introduce the architecture of WDM-PON and present its operation principles and performance characteristics. The network topology is simulated using OptiSystem which is a simulation system used for designing, testing and performance of the optical network.

Speakers: Ms Fatima Zohra BOUGHERAR (Mustapha STAMBOULI University), Ms Ghania BOUALAM (Mustapha STAMBOULI University)

15:34 Peculiarity of mechanical characteristics of nano composites of multiwalled carbon nanotubes and polyethylene, polyvinyl chloride, porous polystyrene

The quasitransversal ultrasonic velocity V┴ = 756± 10 m/sec, shear module G = ρV┴12 = 554 MPa, Poisson coefficient μ ≈ 0,44, Debye temperature θD ≈ 71 K polyethylene with low density high pressure (C2H4)n were determined from the oscilloscopegramma. The ultrasonic (US) attenuation logarithmic decrement was δ_┴≈1,65×〖10〗^(-1).
If dislocation segment ξ(x,y), that are vibrated under the act of tension τ, is charged, additional forces will operate on it FE = eρ(ξ)E and FM = eρ(ξ)[∂ξ/∂t, B], where ρ(ξ) - is the distribution function of electrical charge density on the dislocation segment [1]. The system of equations, which describes the movement of the charged dislocation under act of the mechanical, electrical and magnetic fields, acquires the following kind:

M∂2ξ/∂t2 = Vd ∂2ξ/∂x2 - Q∂ξ/∂t + bτ – bτa - Nj ∂U/∂ξ + eρ(ξ)E + eρ(ξ)[∂ξ/∂t, B], (1)

∂2τ/∂y2 – ρ/G ∂2τ/∂t2 = ρb∂2/∂t2<ʃ0∞[ʃ01ξ(x)dx]N(l)dl>. (2)

Acoustic emission (AE) method was measured the group longitudinal wave velocity in SiO2+TiO2+ZrO2 film there was v║ = l/t ≈ 0,00042 m/0,114 mcsec ≈ 3680 m/sec and the group shear wave velocity was v┴ = l/t ≈ 0,00042 m/0,134 mcsec ≈ 3130 m/sec. Taking into account the value of density ρ ≈ 4,05.103 kg/m3, elastic modulus was determined E = ρ.v║2 ≈ 54,85 GPa and shear modulus was determined G = ρ.v┴2 ≈ 39,68 GPa.
REFERENCES
A.P. Onanko, V.V. Kuryliuk, Y.A. Onanko et al. Journal of nano- and electronic physics. – 2020. – Т. 12, № 4. – 04026. DOI: 10.21272/jnep.12(4).04026.

Speaker: Volodymyr BOYKO (Taras Shevchenko National University of Kyiv)

15:38 Polystyrene Surface Modification for Enhancing Adsorption of Biomolecules: a Surface Plasmon Resonance Study

The study addresses an experimental approach aimed at facilitating the improvement of the Enzyme-Linked Immuno-Sorbent Assay (ELISA) performances. ELISA is a heterogeneous (plate-based) immunological technique widely used as a diagnostic tool. The principle of the assay lies in capturing the biomolecules of interest present in the liquid probe by the capture biomolecules immobilized to the wells of the ELISA microtiter plate. In this scheme, the immobilization mode of the capture biomolecules is of crucial importance for the immunoassay performances. The most common material for the ELISA plates is polystyrene, and the simplest method to control immobilization of the capture biomolecules is partial hydrophilization of the polystyrene surface.
In this study, we show the potentialities of the Surface Plasmon Resonance (SPR) method for detailed real-time label-free monitoring of the sample immunoassay emulating the ELISA protocol. The capture biomolecules were immobilized on polystyrene nanofilms deposited over the SPR chip using a dip-coating technique. The film surface was hydrophilized to different degrees using a wet chemical treatment. The kinetics of the immunoassay was registered by the SPR sensorgram. We assume that this kinetic dependence reproduces the corresponding stages occurring on the ELISA microtiter plate. In our opinion, this approach has a strong promise of facilitating the development of advanced technologies for further improvement of the ELISA technique.

Speaker: Olena Shynkarenko (V. Lashkarev Instititute of Semiconductor Physics NAS of Ukraine)

15:42 Features of adsorption, mechanical properties of nano composites of multiwalled carbon nanotubes and polyethylene, polyvinyl chloride, porous polystyrene

The concentration dependence of the elastic module E(C) in polyvinyl chloride (C2H3Cl)n + multiwalled carbon nanotubes (MWCNT) can be described by a percolation model with the extremely low percolation “threshold” in the range 0.02 ÷ 0.1%.
The Poisson coefficient μ is equal to ratio of relative transversal compression ε┴ to relative longitudinal lengthening ε║ and equal [1]:
μ = ε┴/ε║ = 1/2[1 + 1/1-(V║/V┴)2], (1)
Debye temperature θD was determined after the formula [1]:
θD = h/kB(9NAρ/4πA)1/3 . (1/V║3 + 2/V┴3)1/3, (2)
where kB - Bol'cman constant, h - Plank constant, NA - Avogadro number, A - middle gram-molecular mass, ρ - density, V║ - longitudinal ultrasonic (US) velocity, V┴ - transversal US velocity.
The account of dispersion of elastic mechanical vibrations energy of SiO2+Si plate on the structure defects results in expression for frequency of free vibrations of disk [1]:
ω = [(Dβ2/ρhR4 - 2π2(Q-1/T)2]1/2, (3)
where cylindrical inflexibility of plate D = Eh3/12(1 - μ)2 determined through the elastic module
E = 12ρω2R4(1 - μ)2/β2h2, (4)
plate thickness h and Poisson coefficient μ, β – is a dimensionless coefficient the value of which depends on the number of key circumferences, ρ – the specific density of plate, R - the disk radius, Q-1 – internal friction (IF), T – the disk vibrations period.
REFERENCES
[1] A.P. Onanko, D.V. Charnyi, Y.A. Onanko, M.P. Kulish etc. Conference Proceedings of 18 Geoinformatics: theoretical and applied aspects, 2019, 1-5 (2019). DOI: https://doi.org/10.3997/2214-4609.201902110.

Speaker: Mychaylo BEZZUBCEV (Taras Shevchenko National University of Kyiv)

15:46 X-ray diffraction study of structure of rare-earth orthovanadate nanoparticles doped with calcium

Optical materials based on rare earth vanadates (REVO4) are widely used in science and technology because they are characterized by high absorption in a wide spectral range and effective energy transfer from vanadate host to the RE ions. Such compounds are used as luminescent light emitting materials and luminescent spectral converters. At the last years, nanosized orthovanadates have also attracted considerable research interest as perspective photocatalyst systems for water splitting. All the above mentioned applications require vanadate materials with high efficiency of excitation under light from near UV and violet spectral ranges. In this study, we investigate the structural properties of La1-x-yEry/2Euy/2CaxVO4 where x=0.1, y=0.1; x=0.2, y=0.15, at room temperature. Samples were prepared by aqueous nitrate-citrate sol-gel method. Powder diffraction measurements were performed at P02.1 PETRA III Beamline in DESY using a beam with 0.0207 nm wavelength. Phase analysis of La0.8Er0.05Eu0.05Ca0.1VO4 and La0.65Er0.1Eu0.1Ca0.15VO4 has shown that samples crystalize in two different structure, monoclinic and tetragonal. The starting model for refinement of La0.8Er0.05Eu0.05Ca0.1VO4 is LaVO4 with Monazite type and La0.65Er0.1Eu0.1Ca0.15VO4 is LaVO4 with Zircon type structure. The proportion of the monoclinc to tetragonal phases is depend on amount of dopant. The structures of component phase are refined.
This work has received funding from Ministry of Education and Science of Ukraine under bilateral grant agreement No43-2020 and from the EU-H2020 program under grant agreement No654360 having benefited from the access provided by P02.1 PETRA III beamline of Deutsches Elektronen-Synchrotron (DESY) within the framework of the NFFA-Europe Transnational Access Activity.

Speaker: Ms houri sadat Rahimi Mosafer (Institute of Physics, Polish Academy of Sciences)

15:50 → 16:00 Closing