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ABSTRACT: It was found that for arbitrary high overtone and thin film microwave resonators the results of the measurements of the difference
between frequencies of resonance and antiresonance on any harmonic of the resonator together with the measurement of the frequency
difference between the peculiarities on the frequency dependence of imagine part of the electric impedance of the resonator
give a simple way of the evaluation of the losses in the materials composing resonator structures and of the evaluation of
the electromechanical constant of the piezoelectric film exciting acoustic waves.
Acoustical Physics 04/2012; 56(6):904-908. · 0.70 Impact Factor
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ABSTRACT: Using resonance acoustic spectroscopy method frequency dependencies of acoustic losses in a dense yttrium aluminum garnet (YAG) nanoceramics prepared by the method of nanopowder sintering were studied in the range from 0.3 to 4 GHz. For the acoustic losses in the best available nanoceramics quadratic frequency dependence was experimentally obtained. The best Q-factor of our resonators based on ceramics equals to 20000 on the frequency 1 GHz. Thus the first results obtained show that YAG nanoceramics is promising material for microwave acoustoelectronic devices.
Ultrasonics Symposium, 2008. IUS 2008. IEEE; 12/2008
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ABSTRACT: We have studied symmetric bicrystal Josephson junctions of a new type based on metal oxide superconductors in which the base
planes are misoriented relative to the [100] direction by an angle within 22°–28°. These junctions exhibit record high values
of the critical parameters at T = 77 K: the critical current density reaches I
C = (2−5) × 105 A/cm2 and the characteristic voltage is V
C = I
C
R
N = 0.6−0.9 mV. The properties of the new junctions have been determined for the first time under the influence of monochromatic
microwave radiation in the millimeter wavelength range and have been studied as functions of the magnetic field and temperature.
The observed dependences of the critical current and the Shapiro step height on the electromagnetic field amplitude agree
well with the theoretical predictions according to the resistive shunted junction model of the Josephson junction. The new
junctions can be used in real superconducting devices operating at liquid nitrogen temperatures.
Technical Physics Letters 03/2005; 31(4):332-335. · 0.56 Impact Factor
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ABSTRACT: Using microwave composite resonator spectroscopy and acousto-optic methods, the attenuation of acoustic waves was measured for various propagation directions and wave polarizations in langatate. These data were used for the calculation of a full set of viscosity tensor components of langatate.
Frequency Control Symposium and Exposition, 2004. Proceedings of the 2004 IEEE International; 09/2004
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ABSTRACT: A simple matrix approach to the calculation of multilayered BAW resonators and filters has been developed. Expressions for matrix elements connecting electrical and mechanical characteristics of piezoelectric layers have been obtained. A special case of piezoelectric semiconductor layer has been considered. The possibility of electronic gain in a filter structure has been shown.
Ultrasonics, 2003 IEEE Symposium on; 11/2003
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ABSTRACT: Conductance anomalies at low bias voltages and superconducting currents in Au/YBa2Cu3Ox and Nb/Au/YBa2Cu3Ox heterojunctions in which the c axis of the YBa2Cu3Ox (YBCO) epitaxial film is rotated in the (110) YBCO plane through 11° with respect to the normal to the substrate plane were
studied experimentally. The films were prepared by laser deposition onto (7 2 10)-oriented NdGaO3 substrates. The current-voltage characteristics of the heterojunctions exhibit conductance anomalies at low voltages. The
behavior of these anomalies is studied at various temperatures and in various magnetic fields. The critical current and Shapiro
steps observed in the current-voltage characteristics of Nb/Au/YBa2Cu3Ox were evidence of the Josephson effect in these heterojunctions. The experimental results are analyzed in terms of the model
of the arising of bound states caused by Andreev reflection in superconductors with d-type symmetry of the superconducting order parameter.
Journal of Experimental and Theoretical Physics 11/2002; 95(6):1074-1084. · 1.03 Impact Factor
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ABSTRACT: The growth, crystal structure, and electrophysical properties of YBa2Cu3Ox (YBCO) epitaxial films grown with and without a CeO2 epitaxial sublayer on NdGaO3 (NGO) substrates with the normal to the surface deviating from the [110] axis by 5° to 26.6° around the [001] axis are investigated.
It is shown that the orientation of YBCO epitaxial films grown on such substrates is determined by the existence of symmetry-equivalent
directions in the substrate and in the CeO2 layer, as well as by the rate of film deposition. For a high deposition rate, YBCO films grow on the CeO2 sublayer in the [001] orientation irrespective of the orientation of the substrate and the sublayer. It was found that when
the angle of deviation of the substrate plane is from the (110) NGO plane, twinning of one or both twinning complexes in YBCO
may be suppressed.
Physics of the Solid State 01/2001; 43(9):1611-1620. · 0.71 Impact Factor
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ABSTRACT: We have produced step-edge Josephson junctions on steps in an
epitaxially grown CeO<sub>2</sub> layer on r-cut sapphire. The epitaxial
CeO<sub>2</sub> layer is deposited at high temperature through a MgO/CeO
<sub>2</sub> micromask. The optimum orientation of the step flank (FS)
for grain boundary junction was determined on the basis of known
experimental data of YBa<sub>2</sub>Cu<sub>3</sub>O<sub>x</sub> (YBCO)
film growth on tilted substrates and from analyses of bicrystal grain
boundaries formed in YBCO films along the boundary between the FS and
planar substrate. Atomic force microscopy (AFM) observations of the
steps in which the FS was parallel to the [110]CeO<sub>2</sub> plane
show that the slope angles is in a range from 50° to 70° that
correspond to (111) and (221)CeO<sub>2</sub> crystallographic planes.
The results of dc and microwave measurements of obtained high-T<sub>c
</sub> step-edge junction are presented
IEEE Transactions on Appiled Superconductivity 07/1999; · 1.04 Impact Factor
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ABSTRACT: The problem of acoustic isolation of thin-film piezoelectric
resonators and filters for microwaves is developed. Expressions
describing operation of such devices taking into account losses in all
the layers are derived. The conclusions are supported by numerical
examples
Ultrasonics Symposium, 1998. Proceedings., 1998 IEEE; 02/1998
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ABSTRACT: An analytical expression for the magnitude of the “response” of surface acoustic waves (SAWs) to gases is obtained. It is
tested experimentally. The main features of the detection of gases by means of SAWs are predicted theoretically and confirmed
experimentally. The SAWs in coated and uncoated gas sensors are compared. A technique for using SAWs to determine the relative
changes in the density (Δρ/ρ) and the elastic moduli (ΔC
11/C
11 and ΔC
44/C
44) of films upon the adsorption (desorption) of gases is proposed. The possibility of using this technique to analyze adsorption
and desorption processes is demonstrated. The adsorption properties of polycrystalline, thermally deposited palladium films
before and after low-temperature vacuum annealing, as well as unannealed Pd and Pd:Ni films, are compared. The prospects of
using SAWs to detect gases and to study surface processes induced by them are discussed.
Technical Physics 01/1998; 43(2):201-208. · 0.50 Impact Factor
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ABSTRACT: Results are presented from an experimental study of the crystallographic parameters of (1102)Al2O3/(001)CeO2/(001)YBa2Cu3O7−x
film heterostructures fabricated by cathode sputtering at high substrate temperatures T=600–800°C. It is shown that the main limitation on the temperature for deposition of a YBa2Cu3O7−x
film on a CeO2 surface is due to the chemical interaction between YBa2Cu3O7−x
and CeO2 to form a polycrystalline BaCeO3 layer.
Technical Physics Letters 09/1997; 23(10):738-740. · 0.56 Impact Factor
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ABSTRACT: A modification of the matrix formalism for studying acoustic wave
propagation in anisotropic piezoelectric multilayers is developed. The
modification is based upon the use of the compound matrices, well known
from the theory of the matrices. Using the modified method, analytical
expressions for the relationship between the real and imaginary parts of
the determinant of the boundary conditions are derived. One of the
advantages of the method is demonstrated for thick plates and thick film
structures. On considering the dispersion curves for thick multilayers,
the slow dispersion regions inherent for anisotropic materials are
discovered. The regions are related with the cutoff velocities of the
bulk waves in the film materials
Ultrasonics Symposium, 1996. Proceedings., 1996 IEEE; 12/1996
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ABSTRACT: The magnitude and time variations of the SAW propagation velocity
Δv/v, of the mass and elastic loading, and of the fractional
changes in the density Δρ/ρ and in the elastic modulii
Δc<sub>ij</sub>/c<sub>ij</sub> of Pd films are experimentally
evaluated at room temperature and atmospheric pressure for 0.1, 0.5, 1%
H<sub>2</sub>, 1% CO, 1% N<sub>2</sub>O and 1% NO gas mixtures in pure
nitrogen. Two different thermally evaporated Pd films have been tested:
one as evaporated, the other one after annealing at 423°K and
10<sup>-5</sup> Pa for 15 hours. The annealing is shown to change all
set of the parameters. For not annealed films, hydrogen gives rise to
large variations in the elastic constants (≃5-40%) and to an
increase in the phase velocity; while for annealed films, it produces
small variations in the elastic constants (≃1-2%) and a decrease in
the phase velocity. The difference is attributed to weakly and strongly
coupled oxygen preadsorbed in the film. The results obtained can allow
an improvement of Pd-based sensors
Ultrasonics Symposium, 1996. Proceedings., 1996 IEEE; 12/1996
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ABSTRACT: SAW delay lines with three different geometries are experimentally
investigated as gas detectors and suggested for sensing of corrosive
analytes. The main feature of these geometries is the complete
separation between electromechanical transducers and sorbent film
deposited on the opposite sides of substrate Experiments are
accomplished at room temperature and atmospheric pressure with delay
lines implemented on glass, quartz and Bi<sub>12</sub>SiO<sub>20</sub>
substrates and operating at frequencies 28-263 MHz. Pt film and H<sub>2
</sub> exposure are exploited as an example to demonstrate applicability
of the proposed geometries as gas detectors. Comparison between the
uncommon and common delay lines as gas sensors shows approximately the
same gas sensitivity (50 ppm at 0.1% Hz), but higher insertion loss for
uncommon devices. Achievable limits of the losses are discussed. Gas
responses for SAW delay lines with different geometries, materials and
wrap-around transits are presented
Ultrasonics Symposium, 1995. Proceedings., 1995 IEEE; 12/1995
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ABSTRACT: Numerical estimations of the mass and elastic loadings are
performed for different possible material combinations. In order to do
this, the density and elastic constants of the film are changed
consequently and one by one for each of the combination selected in
accordance with Farnell-Adler's theory. In addition, the perturbation
approach is applied to analyse the SAW gas response in analytical form.
On considering, as an example, Pd coated SAW delay lines exposed to
hydrogen, the relative changes in Pd parameters are measured, the mass
and elastic loadings are estimated and the SAW hydrogen responses are
theoretically predicted and experimentally verified. An increase of a
factor 10 in the SAW gas response is demonstrated for Pd film deposited
on different substrate materials and/or crystallographic orientations
Ultrasonics Symposium, 1995. Proceedings., 1995 IEEE; 12/1995
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ABSTRACT: The relative fraction r of the elastic energy of an acoustic mode localized in a supported film is shown to play an important role in some applications of layered structures such as electroelastic effect, gas sensing and acoustic characterization. Computer simulation of the parameter r as a function of the film thickness normalized to the acoustic wavelength is performed for different possible material combinations in accordance with Farnell-Adler's scheme. Some general features of the parameter r are discussed. Measurements of acoustic attenuation and temperature coefficient of delay, are shown to correlate with the behavior of this parameter for Rayleigh and Sezawa modes and for both conditions of slow film on fast substrate and fast film on slow substrate. The analysis and experiments have been carried out on layered structures made of AlN and ZnO films on glass, fused quartz, and Si substrates
Ultrasonics Symposium, 1994. Proceedings., 1994 IEEE; 12/1994
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Surface Waves in Solid and Layered Structures, 1994, and National Conference on Acoustoelectronics. 1994 International Symposium on. Program and Abstracts; 06/1994
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ABSTRACT: SnO<sub>2</sub> films have been recently used as reactive materials in gas sensors based on change of the electrical resistivity under gas exposure. In view of potential application of these films to surface acoustic waves (SAW) sensors, knowledge of their elastic properties is of current interest. We report here on results of the elastic characterization of SnO<sub>2</sub> films, with thicknesses in the range between 0.2 and 3 μm, prepared by reactive magnetron sputtering. Brillouin light spectroscopy has been exploited in older to determine the phase velocity of both surface and bulk acoustic modes on films deposited on (001)-Si substrates. Moreover, an ultrasonic technique has been used to measure the group velocity of the Rayleigh wave in layered structures consisting of a piezoelectric plate (quartz or LiNbO<sub>3</sub>) coveted with a SnO<sub>2</sub> overlayer. The whole information gained by use of these two techniques has been used for determining the effective elastic constants and the mass density of the SnO<sub>2</sub> films. SAW attenuation and temperature coefficient of delay on the film material have been also evaluated
Ultrasonics Symposium, 1993. Proceedings., IEEE 1993;
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ABSTRACT: Growth, structure and physical properties of YBa2Cu3Ox (YBCO) thin films and YBCO/CeO2 heterostructures on tilted-axes NdGaO3 (NGO) substrates with an inclination of normal of the substrate from the [1 1 0] axis were investigated. It was shown that the orientation of epitaxial YBCO thin films is influenced by the deposition rate and the presence of symmetrical-equivalent directions [1 1 0] and [1 0] in the substrate and [1 0 0], [0 1 0] and [0 0 1] in the CeO2 layer. Domain structure and morphology of the YBCO thin film surface change with an increase of the inclination angle. The YBCO thin films on the tilted-axes substrates are twinned of the same way as on (1 1 0) NGO substrates. However, formation of one or both twinning complexes is suppressed with an increase of the inclination angle.
Physica C: Superconductivity.
