Fomos Materials

Moscow, Russia

Fomos Materials

Moscow, Russia
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Spassky D.A.,University of Tartu | Spassky D.A.,Moscow State University | Brik M.G.,University of Tartu | Brik M.G.,Chongqing University of Posts and Telecommunications | And 6 more authors.
Journal of Luminescence | Year: 2016

Luminescent, optical and electronic properties of La3Ta0.5Ga5.5O14 single crystals grown in different atmospheres are presented. The absorption bands at 255, 290, 350 and 480 nm were detected; the intensity of bands increases with the concentration of oxygen in the growth atmosphere. It is shown that the shift of the fundamental absorption edge with the temperature obeys Urbach rule. The corresponding fitting allowed to estimate the slope coefficient σ=0.35, which implies self-trapping of excitons in La3Ta0.5Ga5.5O14. Calculations of the band structure, partial densities of states and reflectivity spectra were performed. The bandgap of La3Ta0.5Ga5.5O14 was determined as Eg=5.6 eV. The luminescence properties under UV, VUV and X-ray excitation were studied. Intrinsic emission band at 440-450 nm is attributed to the excitons self-trapped at TaO6 molecular complexes. Extrinsic emission bands at 410, 440 and 550 nm are attributed to the emission of excitons trapped by antisite defects, F-centers and oxygen deficient oxyanionic complexes. © 2016 Elsevier B.V. All rights reserved.


Roshchupkin D.,Russian Academy of Sciences | Plotitcyna O.,Russian Academy of Sciences | Irzhak D.,Russian Academy of Sciences | Emelin E.,Russian Academy of Sciences | And 3 more authors.
IEEE International Ultrasonics Symposium, IUS | Year: 2013

A five-component crystal of lanthanum-gallium silicate group La 3Ga5.3Ta0.5Al0.2O14 (LGTA) was grown by the Czochralski method. The LGTA crystal possesses unique thermal properties and substitution of Al for Ga in the unit cell leads to a substantial increase of electrical resistance at high temperatures. The unit cell parameters of LGTA were determined by powder diffraction. X-ray topography was used to study the crystal structure perfection: the growth banding normal to the growth axis were visualized. Excitation and propagation of surface acoustic waves (SAW) were studied by the double crystal X-ray diffraction at the BESSY II synchrotron radiation source. The analysis of the diffraction spectra of acoustically modulated crystals permitted the determination of the velocity of acoustic wave propagation and the power flow angles in different acoustic cuts of the LGTA crystal. © 2013 IEEE.


Roshchupkin D.,Russian Academy of Sciences | Irzhak D.,Russian Academy of Sciences | Plotitcyna O.,Russian Academy of Sciences | Emelin E.,Russian Academy of Sciences | And 3 more authors.
2013 Joint European Frequency and Time Forum and International Frequency Control Symposium, EFTF/IFC 2013 | Year: 2013

X-ray diffraction on the La3Ga5SiO14 (LGS) crystal modulated by surface (SAW) and pseudo-surface acoustic waves (PSAW) with wavelength of Λ=6 μm was studied using a double axis X-ray diffractometer at the BESSY II synchrotron radiation source. The propagation of SAW and PSAW leads to sinusoidal modulation of the crystal lattice and gives rise to diffraction satellites on the rocking curve, with the intensity and angular divergence between the diffraction satellites depending on the wavelength and amplitude of the crystal lattice acoustic modulation. The analysis of diffraction spectra enables the determination of the amplitude and acoustic wavelengths, and power flow angles of acoustic energy propagation. The investigation of acoustic wave fields showed that PSAW is a flowing back wave. © 2013 IEEE.


Richter D.,Clausthal University of Technology | Sakharov S.,FOMOS Materials | Forsen E.,Danish Technological Institute DTI | Mayer E.,Albert Ludwigs University of Freiburg | And 2 more authors.
Procedia Engineering | Year: 2011

Wireless surface acoustic wave devices based on langasite allow sensor operation in high-temperature environments. While langasite shows piezoelectric behavior up to temperatures close to its melting point of 1470 °C, the stability of thin film electrodes for excitation of acoustic waves limits the application temperature. Different metal and ceramic based thin films are tested regarding their applicability as electrode materials for wireless surface acoustic wave devices at temperatures above 600 °C. The devices should withstand temperatures of 800 °C for at least several hours. The high-temperature stability of platinum, platinum-rhodium, iridium as well as lanthanum strontium manganite (LSM) based electrodes is characterized using electrical measurements, x-ray diffraction (XRD) measurements and scanning electron microscopy (SEM) imaging. SAW devices with Ti/Pt thin film electrodes are operated up to temperatures of 800 °C. LSM/Pt films exhibit a good stability up to temperatures of 800 °C. Above 600 °C its resistance is comparable to platinum films. © 2011 Published by Elsevier Ltd.


Forsen E.,Danish Technological Institute DTI | Nilsson D.,Danish Technological Institute DTI | Ballandras S.,French National Center for Scientific Research | Mayer E.,Albert Ludwigs University of Freiburg | Sakharov S.,FOMOS Materials
Procedia Engineering | Year: 2011

Jet-and-flash nano imprint lithography (NIL) has successfully been utilized for the fabrication of surface acoustic wave (SAW) sensors. These SAW sensors will be used for passive wireless sensing of physical parameters, e.g. the temperature inside gas turbine engines. This is the first time metal lift-off processes based on jet-and-flash NIL have been established on the piezoelectric substrate material lanthanum gallium silicate (Langasite). NIL produced Langasite SAW temperature sensors have successfully been fabricated on various crystal cuts and SAW electrode metallization using Ti/Pt and Ti/Ni have been realized. Langasite based SAW sensors are to be used for passive wireless temperature monitoring at up to 950 degrees Celsius. © 2011 Published by Elsevier Ltd.


Sakharov S.,Fomos Materials | Naumenko N.,Moscow Technical University of Communication and Information | Zabelin A.,Fomos Materials | Zhgoon S.,Moscow Power Engineering Institute
IEEE International Ultrasonics Symposium, IUS | Year: 2011

Experimental SAW resonator structures with iridium electrodes were fabricated on Y-cut of langasite with few different propagation directions and their characteristics were measured in a wide temperature interval, up to 700°C, and compared with simulations. Between two sets of material constants reported by Bungo one set was selected as providing much better agreement with experiments, for the analyzed orientations. Further improvement of simulation accuracy was achieved via after-correction of the calculated temperature characteristics using auxiliary function extracted from experimental data. This approach was used to predict resonator characteristics in orientation with Euler angles (0°, 22°, 90°), in which Bluestein-Gulyaev wave propagates, and provided excellent agreement between experiments and simulations, in a wide temperature interval. © 2011 IEEE.


Sakharov S.,Fomos Materials | Kondratiev S.,Fomos Materials | Zabelin A.,Fomos Materials | Naumenko N.,Moscow Institute of Steel And Alloys | And 3 more authors.
Proceedings - IEEE Ultrasonics Symposium | Year: 2010

Different cuts of langasite were investigated theoretically andexperimentally as candidates for high temperature sensors utilizing SAWresonators and reflecting SAW tags. Single port SAW resonators with centralfrequencies close to 170, 200 and 433 MHz with W, Ir and Pt electrodes ofdifferent thickness were fabricated and their characteristics were measured asfunctions of temperature. An approach to SAW device encapsulation, which helpsto avoid stress development during heating to high temperatures, was suggestedand tested. The damage of the langasite surface during heating to hightemperature is strong in the cut family with Euler angles (0°, 138.5°,ψ), while orientations with Euler angles (0°, 90°, ψ) and(0°, 22°, ψ) were found to be more resistant to heating. In thelatter cut family, two cuts, (0°, 22°, 31.5°) and (0°, 22°,90°) can provide zero power flow angle and sufficient piezoelectriccoupling. COM parameters of SAW resonators with W, Ir and Pt electrodes,including complex reflection coefficient, were calculated as functions ofelectrode thickness and measured in the wide temperature range. The frequencyresponses were described by COM equations and the fitted COM-parameters werecompared to their simulated values. Resonators show high Q and their performanceis perfectly described by COM equations © 2010 IEEE.


Roshchupkin D.,Russian Academy of Sciences | Plotitcyna O.,Russian Academy of Sciences | Irzhak D.,Russian Academy of Sciences | Emelin E.,Russian Academy of Sciences | And 2 more authors.
2014 European Frequency and Time Forum, EFTF 2014 | Year: 2014

A five-component ordered crystal of lanthanum-gallium silicate family Ca3NbGa3Si2O14 (CNGS) was grown by the Czochralski method. The unit cell parameters were determined by using the powder diffraction technique. Independent piezoelectric strain coefficients d11 and d14 were measured by high-resolution X-ray diffraction under the external electric field application which caused changes in the interplanar spacing because of the reverse piezoelectric effect. Surface acoustic wave (SAW) propagation in CNGS crystal was investigated by X-ray diffraction method at the synchrotron radiation source BESSSY II. The velocities of SAW propagation and power flow angles were measured in the Y-, X-, and yxl/+36°-cuts of CNGS crystal. © 2014 IEEE.


Kozlova N.S.,National University of Science and Technology "MISIS" | Busanov O.A.,Fomos Materials | Zabelina E.V.,National University of Science and Technology "MISIS" | Kozlova A.P.,National University of Science and Technology "MISIS" | Bykova M.B.,National University of Science and Technology "MISIS"
Crystallography Reports | Year: 2016

The hypotheses about the nature of color centers in langasite family crystals that are discussed in the literature are analyzed. Optical transmission spectra in the wavelength range of 200–800 nm are recorded for langasite and langatate crystals grown in atmospheres of argon and argon mixed with oxygen in different concentrations, both in the initial state and after isothermal annealings at 1000°C in nitrogen, in air, or in vacuum. Dichroism is observed in langasite and langatate crystals, and spectral dependences of the degrees of dichroism are plotted. © 2016, Pleiades Publishing, Inc.


Buzanov O.A.,Fomos Materials | Kozlova N.S.,National University of Science and Technology "MISIS" | Zabelina E.V.,National University of Science and Technology "MISIS" | Kozlova A.P.,National University of Science and Technology "MISIS" | Siminel N.A.,National University of Science and Technology "MISIS"
Russian Microelectronics | Year: 2011

The optical transmission spectra and electrical properties of langasite (La 3Ga 5SiO 14) and lan- gatate (La 3Ta 0.5Ga 5.5O 14) single crystals are studied experimentally in relation to the oxygen concentration in an argon-oxygen atmosphere of growth. The variation of langatate conductivity with temperature under a constant electric field is examined over the range 20 to 500°C. Its dependence on current-carrying material is investigated for an Ir, Au/Ti, or Ag/Cr coating. © Pleiades Publishing, Ltd., 2011.

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