Igor Ostrovskii - Academia.edu (original) (raw)

Papers by Igor Ostrovskii

arXiv (Cornell University), Oct 24, 2016

The three dimensional vibrations in a periodically poled ZX-cut Lithium Niobate thin bar with 0.3... more The three dimensional vibrations in a periodically poled ZX-cut Lithium Niobate thin bar with 0.3mm long domains are considered. The acoustical vibrations may be excited by the 1) longitudinal acousto-electric current when a radio frequency voltage is parallel to the x-axis, and 2) transverse electric field when a radio frequency voltage is parallel to the z-axis. The computations by the Final Element Method reveal all the three displacements along the x, y, and z crystallographic axes. The amplitudes may be different for two types of vibration excitations. The positions of peaks in admittance versus frequency correlate with the frequencies of maximum acoustic amplitudes. The superlattice with 0.3-mm long domains along the x-axis is fabricated in the z-cut 0.5-mm-thick wafer. The experimental data on the radio frequency admittance versus frequency is in agreement with the corresponding theoretical computations.

Plate acoustic waves (PAW) propagating along X-axis in the Z-cut wafer of a single crystal of lit... more Plate acoustic waves (PAW) propagating along X-axis in the Z-cut wafer of a single crystal of lithium niobate are considered theoretically and experimentally. For eight lowest PAW modes, the dispersion curves for wavenumber k(f) are calculated by the equations of motion and electrodynamics, by the Finite Element Method, and then measured experimentally. The spectra k(f) obtained by the numerical solution and FEM-simulation are in good agreement, and experimental measurements agree with theoretical predictions. The PAW modes are identified by the components of their total acoustic displacements and cutoff frequencies. Analysis of the longitudinal and normal acoustical displacements permits to find PAW mode capable for usage in ultrasonic actuators. The results obtained may be useful for ultrasonic transducers, acousto-electronic and acousto-optic applications, and ultrasonic motors/actuators fabricated in the Z-cut ferroelectric lithium niobate wafers including periodically poled wav...

Proceedings of Meetings on Acoustics, 2017

The spectra of photoluminescence (PL) from a YZ-cut Lithium niobate (LN) plate reveal point defec... more The spectra of photoluminescence (PL) from a YZ-cut Lithium niobate (LN) plate reveal point defects of heavy metals Fe and Ba. The distribution of point defects (DPD) is nonuniform and exhibits peaks and valleys, in a direction parallel to the z-axis. The distance between consecutive peaks and consecutive valleys is not more than a few mm. The point defects are sensitive to local electric polarization and influence the electromechanical transformation (EMT) at the local point of the crystal. The EMT is estimated by reading an electric potential (V) generated while applying a constant mechanical stress, at steps of hundreds of micron parallel to the z-axis. The distribution of EMT in LN is nonuniform; the distance between consecutive peaks and consecutive valleys is similar to the DPD. Higher the concentration of point defects more is the EMT, and lower the concentration of point defects lower is the EMT. The point defects are manifested as peaks and valleys in the frequency dependence of admittance measurements. The presence of point defects excites ultrasonic modes in the crystal when radio-frequency current propagates through it.

arXiv (Cornell University), Jul 4, 2003

A reorientation of the ferroelectric domains under an action of ultrasound in LiNbO 3 is observed... more A reorientation of the ferroelectric domains under an action of ultrasound in LiNbO 3 is observed for the first time. The involvement of the ferroelectric domain boundaries is experimentally identified by the analysis of X-ray reflection and crystal etching. The reorientation of the domains takes place under acoustic deformation of the order of 10-5 in megahertz frequency range.

The sonoluminescence of ionic semiconductors were studied. The main attention is paid to threshol... more The sonoluminescence of ionic semiconductors were studied. The main attention is paid to threshold phenomena which accompany the light irradiation, namelypoint defect creation and nonlinear ultrasound wave attenuation. The model for description of processes under investigation which connects the sonoluminescence excitation with the onset of point defects (vacancies and intersticials) generation by moving under ultrasound action screw dislocation with a jog. The attempt is made to estimate the parameters of crystals which define the jog motion in its cristal relief.

Journal of Optics A: Pure and Applied Optics, 2001

The Journal of the Acoustical Society of America, 2013

Excitation of the acoustic plate waves (PAW) in ferroelectric wafers with microscale domains and ... more Excitation of the acoustic plate waves (PAW) in ferroelectric wafers with microscale domains and nanoscale interdomain walls is investigated theoretically and experimentally. The periodically poled structures were fabricated in the Z-cut 0.5-mm-thick LiNbO3 wafers. Rf-current applied along the X-axis generates PAW in the fabricated multidomain acoustic superlattices having stop-bands and acoustic Brillouin zones. Two main effects are observed. First, a frequency of maximum acoustic amplitude does not coincide with the domain resonance frequency when a half-wavelength equal to domain length. Second, instead of known single-frequency domain resonance such as in bulk crystals, the series of two or more transduction resonances do exist. The theory, simulation, and experiments allow concluding that the transduction multi-resonances occur due to ultrasound diffraction by the interdomain nano-walls when the acoustic wavelength is close to multidomain period; it happens near acoustic Brillo...

arXiv (Cornell University), Dec 24, 2004

Within a nanoscale volume, an acoustic wave interacts with radiation defects in ionic solids. The... more Within a nanoscale volume, an acoustic wave interacts with radiation defects in ionic solids. The radiation-induced optical absorption in ionic crystals is remarkably removed by a room-temperature ultrasonic treatment of the crystals. It is shown that the effect can be explained by defect migration processes occurring in ultrasonic fields. The inter-ion charge exchange, termed as acoustically-stimulated chemical reaction, is furthermore suggested to occur affecting the defect migration. This new method of a cold annealing of radiation defects in solids can be regarded as nanoacoustic defect manipulation.

The Journal of the Acoustical Society of America, 2020

The optical experiments with suspended quartz crystals reflecting Laser-Doppler-Vibrometer (LDV) ... more The optical experiments with suspended quartz crystals reflecting Laser-Doppler-Vibrometer (LDV) beam reveal an effect of crystal pendulum vibrations initiated by Sun's radiation of heavy particles. The LDV measures speed S(t) of oscillating crystal surface. The Fourier-transform of S(t) returns a spectrum of the acoustic vibrations with a few hertz frequency. The S(t) is a sine-type curve with amplitude depending on the time and space orientation of crystal axes. Maximum vibrational speed and corresponding crystal displacement from a position of equilibrium are observed when quartz piezoelectric axis is aimed toward the Sun. Experimental evidences exclude involvement of any electro-magnetic wave. The theoretical calculations for an oscillator driven by a periodic pulse-force are compared to the experimentally detected oscillations. The computations give a work done by an external force to move the crystal from its equilibrium to maximum displacement. It yields a mass of a think...

Journal of Physical Studies, 1998

A new acousto-electrical method making use of transient transverse acoustoelectric voltage (TAV) ... more A new acousto-electrical method making use of transient transverse acoustoelectric voltage (TAV) to study solid state structures is reported. This voltage arises after a surface acoustic wave (SAW) generating the signal is switched off. Related measurements consist in detecting the shape of transient voltage and its spectral and temperature dependence. Both theory and experiment show that this method is an effective tool to characterize trapping centers in the bulk as well as at surfaces or interfaces of epitaxial semiconductor structures.

Proceedings of Meetings on Acoustics, 2018

The new kind of experiments involving free vibrating crystal and space orientation of its crystal... more The new kind of experiments involving free vibrating crystal and space orientation of its crystallographic axes with respect to the stars are presented. The discovered "crystal-star effect" consists of changes in the vibrating crystal under the influence of cosmic radiation. It allows direct detection of the dark matter. The crystal-star nonclassical nonlinearity is demonstrated by measuring radio-frequency admittance, Y(F), from the quartz resonators near frequency F=10 MHz. The dark particles of (4+-1.5)x10E15 eV are directly detected, this energy corresponds to dark matter candidates Q-balls. The measured speed of particles in space is (249+-1.5) km/sec. One may call revealed particles "navitens" as they are energetic, invisible/unknown in experimental astronomy and high-energy physics. The changes in Y(F) are observed when specific crystallographic axis is directed toward the Sun, or Milky Way center, or star Deneb. The navitens may transfer their energy and linear momentum to a media of propagation. The independent test with a video camera captures the rocking-type motion of some samples under the influence of these particles. The navitens may create the micro-voids and tracks in a vibrating transparent dielectric. The physics of the crystal-star effect may be associated with the gravitational and quantum properties of the detected particles.

Proceedings of Meetings on Acoustics, 2018

The point defects in the spectra of photoluminescence of Lithium niobate (LN) and Lithium tantala... more The point defects in the spectra of photoluminescence of Lithium niobate (LN) and Lithium tantalate (LT) can be categorized as noble gases, heavy metals, and others. The distribution of charged defects (DCD) reveals peaks and valleys in a direction perpendicular to the z-axis, in both single crystals (SC) and periodically poled (PP) crystals. The distance between consecutive peaks and valleys equals the length of a ferroelectric domain in PPLT. The position of the ferroelectric domain wall with respect to point defects extrema is different in PPLT in comparison to PPLN. The DCD influences acousto-electric properties including electromechanical transduction (EMT) and electromechanical coupling coefficient (ECC), in a direction perpendicular to the z-axis. The results may be used to explain nonclassical nonlinearity in LN and LT crystals.

Acta Universitaria, 2005

Optical spectra of light reflection are detected under an influence of ultrasonic wave (UW)on a G... more Optical spectra of light reflection are detected under an influence of ultrasonic wave (UW)on a GaAs wafer. The differential spectrum is calculated as a difference between those taken under UW and without that influence on a sample. This acousto-optic differential reflectance(AODR) spectrum contains some bands that represent the energetic levels of the shallow centers in a sample. A physical basis of this technique is related to a perturbation of local states by UW. Here, a method is developed for characterization of local states at the surfaces and interfaces in crystals and low-dimensional epitaxial structures based on microelectronics materials. A theoretical model is presented to explain AODR spectra. Also, experiments using epitaxial GaAs structures doped by Te were made. Finally, theoretical and experimental results show that acousto-optic reflectance is an effective tool for characterization of shallow trapping centers in epitaxial semiconductor structures.

The Journal of the Acoustical Society of America, 2017

The photoluminescence (PL) from point defects in ferroelectric phononic crystal (FPC) is investig... more The photoluminescence (PL) from point defects in ferroelectric phononic crystal (FPC) is investigated at room temperature. The FPC consists of periodically poled domains 0.45-mm-long each along the x-axis in the 0.5-mm-thick z-cut LiNbO3 wafer. The spectra of PL are excited by 310 nm ultraviolet light and registered in the range of 350 to 900 nm. The PL spectra reveal different point defects including F-center, Ba, Ar, Ne, Cr, K, Fe+, Xe, and others. The electrically active defects such as F-center and Fe+ are expected to be sensitive on a local electric polarization. In a FPC, the ferroelectric neighboring domains are inversely poled and have an opposite electric polarization. The change from polarization “up” to polarization “down” happens across so called interdomain wall. The point defect concentrations along the neighboring domains are researched by PL-scanning, consisting of taking PL-spectra from narrow zones across the domain structure along the x-axis. This scanning reveal a nonuniform distributi...

Journal of the Acoustical Society of America, 2016

Nonclassical nonlinearity (NN) in ultrasound attenuation and acoustic memory in LiNbO3.may be con... more Nonclassical nonlinearity (NN) in ultrasound attenuation and acoustic memory in LiNbO3.may be connected to crystal defects. The optical spectra of photoluminescence (PL) and absorption taken from 350—900 nm reveal multiple point defects and impurities such as F-center, NbLi+, Fe, Ba, Ar, Xe and others. The spectra are taken at room temperature from the Czochralski grown bulk crystals and wafers. The samples are scanned by taking PL spectra from different locations along the z- and y-axes. The data from several samples reveal a nonuniform distribution of the defects along the crystallographic axes. The dependencies of PL peaks versus position have a sine-like component on top of some constant intensity. For instance, a scan for F-center has a period (P) from 0.27 to 0.75 mm and for Ba impurity from 0.25 to 0.75 mm in bulk crystals. In the wafers, P may be smaller, that is 0.1 mm and smaller. However, a ratio of maxima to minima in PL peaks is higher for bigger P. The overall spread o...

Journal of the Acoustical Society of America, 2016

The vibrations and matching acousto-electric resonances in 3-D periodically poled LiNbO3 bar are ... more The vibrations and matching acousto-electric resonances in 3-D periodically poled LiNbO3 bar are investigated. Two superlattices are fabricated in the z-cut 0.5-mm-thick wafers. They consist of the inversely poled domains of 0.45- or 0.3-mm long along the x-axis and tens-mm wide along the y-axis. Metal electrodes are deposited at the ends of superlattices along the x-axis. Experimentally, the vibrations are excited in MHz frequency range by the electric current along the x-axis or acoustic burst propagating along this axis. The function generator, digital oscilloscope, and spectrum analyzer allow measuring frequency dependencies of the acousto-electric resonances in rf-admittance Y(f), and transmission coefficient for acoustic burst propagating through the superlattice. The finite element method computations yield the acoustic displacements and acousto-electric admittance versus frequency. The displacements have three components along the x, y, and z axes. They are minimized within ...

Journal of the Acoustical Society of America, 2016

The observation of a nonstructural acousto-injection luminescence (NAIL) from metallized LiNbO3 w... more The observation of a nonstructural acousto-injection luminescence (NAIL) from metallized LiNbO3 wafers is reported. The X- and Y-cut plates with linear dimensions of a few mm and silver paste electrodes on opposite surfaces are investigated. The experiments are done at room temperature. The fundamental shear modes are excited at MHz-frequencies. We measure the spectra of NAIL, acousto-electric resonance/antiresonance properties, X-ray diffraction rocking curves, acoustic emission accompanying NAIL, and photoluminescence. The NAIL and associated effects appear above a certain threshold acoustical strain of e = 10-5. The results are explained in the terms of considerable piezoelectric fields, yielding the charge injection from the metal contacts into crystal along with the strong mechanical stresses leading to dislocations motion. The acoustic emission and X-Ray rocking curves disclose the dislocation motion under e > 10-5. The involvement of the microstructural non-uniformities in...

The Journal of the Acoustical Society of America, 2014

The acoustical transduction in an array of ferroelectric domains with alternating piezoelectric c... more The acoustical transduction in an array of ferroelectric domains with alternating piezoelectric coefficients is characterized by multi-frequency resonances, which occur at the boundary of the acoustic Brillouin zone (ABZ). The resonances correspond to two successive domain excitations in the first and second ABZ correspondingly, where the speed of ultrasound is somewhat different. An important parameter for acoustical transduction is the electric impedance Z. The results of the theoretical and experimental investigations of Z in a periodically poled LiNbO3 are presented. The magnitude and phase of Z depend on the array parameters including domain resonance frequency and domain number; Z of arrays consisting of up to 88 0.45-mm-long domains in the zx-cut crystal are investigated. The strong changes in Z-magnitude and phase are observed in the range of 3–4 MHz. The two resonance zones are within 3.33 ± 0.05 MHz and 3.67± 0.05 MHz. The change in domain number influences Z and its phase...

The periodically poled ferroelectric wafer is a two-dimensional phononic superlattice. The import... more The periodically poled ferroelectric wafer is a two-dimensional phononic superlattice. The important applications of such a solid include novel ultrasonic transducers at the micro/nano-scale for low intensity ultra-sonography, ferroelectric data storage, and development of very high frequency chips for next generation communication and information technologies, and others. Usually, the transformations between the electrical and mechanical energies are required in the applications. In this work, we find the frequency characteristics for an effective acousto-electric interaction in a two-dimensional phononic superlattice inserted in LiNbO3 wafer.

Fabrication of the bimorph lithium niobate cantilevers involves a micro machining of a z-cut wafe... more Fabrication of the bimorph lithium niobate cantilevers involves a micro machining of a z-cut wafer to create a multidomain structure. After etching, the bimorph ferroelectric cantilevers are fabricated at the locations near interdomain walls. Cantilever vibrations are excited by rf voltage due to piezoelectric effect in a ferroelectric chip, and optical detection is employed to pickup the vibrations. The self-assembling layers of two different Silanes are chemically deposited on the micro cantilevers. The layers are detected independently by two methods including a low frequency shift of cantilever natural vibrations, and Raman spectral lines from the Silane layers. Possible applications include smart biosensors in a real time domain.

arXiv (Cornell University), Oct 24, 2016

The three dimensional vibrations in a periodically poled ZX-cut Lithium Niobate thin bar with 0.3... more The three dimensional vibrations in a periodically poled ZX-cut Lithium Niobate thin bar with 0.3mm long domains are considered. The acoustical vibrations may be excited by the 1) longitudinal acousto-electric current when a radio frequency voltage is parallel to the x-axis, and 2) transverse electric field when a radio frequency voltage is parallel to the z-axis. The computations by the Final Element Method reveal all the three displacements along the x, y, and z crystallographic axes. The amplitudes may be different for two types of vibration excitations. The positions of peaks in admittance versus frequency correlate with the frequencies of maximum acoustic amplitudes. The superlattice with 0.3-mm long domains along the x-axis is fabricated in the z-cut 0.5-mm-thick wafer. The experimental data on the radio frequency admittance versus frequency is in agreement with the corresponding theoretical computations.

Plate acoustic waves (PAW) propagating along X-axis in the Z-cut wafer of a single crystal of lit... more Plate acoustic waves (PAW) propagating along X-axis in the Z-cut wafer of a single crystal of lithium niobate are considered theoretically and experimentally. For eight lowest PAW modes, the dispersion curves for wavenumber k(f) are calculated by the equations of motion and electrodynamics, by the Finite Element Method, and then measured experimentally. The spectra k(f) obtained by the numerical solution and FEM-simulation are in good agreement, and experimental measurements agree with theoretical predictions. The PAW modes are identified by the components of their total acoustic displacements and cutoff frequencies. Analysis of the longitudinal and normal acoustical displacements permits to find PAW mode capable for usage in ultrasonic actuators. The results obtained may be useful for ultrasonic transducers, acousto-electronic and acousto-optic applications, and ultrasonic motors/actuators fabricated in the Z-cut ferroelectric lithium niobate wafers including periodically poled wav...

Proceedings of Meetings on Acoustics, 2017

The spectra of photoluminescence (PL) from a YZ-cut Lithium niobate (LN) plate reveal point defec... more The spectra of photoluminescence (PL) from a YZ-cut Lithium niobate (LN) plate reveal point defects of heavy metals Fe and Ba. The distribution of point defects (DPD) is nonuniform and exhibits peaks and valleys, in a direction parallel to the z-axis. The distance between consecutive peaks and consecutive valleys is not more than a few mm. The point defects are sensitive to local electric polarization and influence the electromechanical transformation (EMT) at the local point of the crystal. The EMT is estimated by reading an electric potential (V) generated while applying a constant mechanical stress, at steps of hundreds of micron parallel to the z-axis. The distribution of EMT in LN is nonuniform; the distance between consecutive peaks and consecutive valleys is similar to the DPD. Higher the concentration of point defects more is the EMT, and lower the concentration of point defects lower is the EMT. The point defects are manifested as peaks and valleys in the frequency dependence of admittance measurements. The presence of point defects excites ultrasonic modes in the crystal when radio-frequency current propagates through it.

arXiv (Cornell University), Jul 4, 2003

A reorientation of the ferroelectric domains under an action of ultrasound in LiNbO 3 is observed... more A reorientation of the ferroelectric domains under an action of ultrasound in LiNbO 3 is observed for the first time. The involvement of the ferroelectric domain boundaries is experimentally identified by the analysis of X-ray reflection and crystal etching. The reorientation of the domains takes place under acoustic deformation of the order of 10-5 in megahertz frequency range.

The sonoluminescence of ionic semiconductors were studied. The main attention is paid to threshol... more The sonoluminescence of ionic semiconductors were studied. The main attention is paid to threshold phenomena which accompany the light irradiation, namelypoint defect creation and nonlinear ultrasound wave attenuation. The model for description of processes under investigation which connects the sonoluminescence excitation with the onset of point defects (vacancies and intersticials) generation by moving under ultrasound action screw dislocation with a jog. The attempt is made to estimate the parameters of crystals which define the jog motion in its cristal relief.

Journal of Optics A: Pure and Applied Optics, 2001

The Journal of the Acoustical Society of America, 2013

Excitation of the acoustic plate waves (PAW) in ferroelectric wafers with microscale domains and ... more Excitation of the acoustic plate waves (PAW) in ferroelectric wafers with microscale domains and nanoscale interdomain walls is investigated theoretically and experimentally. The periodically poled structures were fabricated in the Z-cut 0.5-mm-thick LiNbO3 wafers. Rf-current applied along the X-axis generates PAW in the fabricated multidomain acoustic superlattices having stop-bands and acoustic Brillouin zones. Two main effects are observed. First, a frequency of maximum acoustic amplitude does not coincide with the domain resonance frequency when a half-wavelength equal to domain length. Second, instead of known single-frequency domain resonance such as in bulk crystals, the series of two or more transduction resonances do exist. The theory, simulation, and experiments allow concluding that the transduction multi-resonances occur due to ultrasound diffraction by the interdomain nano-walls when the acoustic wavelength is close to multidomain period; it happens near acoustic Brillo...

arXiv (Cornell University), Dec 24, 2004

Within a nanoscale volume, an acoustic wave interacts with radiation defects in ionic solids. The... more Within a nanoscale volume, an acoustic wave interacts with radiation defects in ionic solids. The radiation-induced optical absorption in ionic crystals is remarkably removed by a room-temperature ultrasonic treatment of the crystals. It is shown that the effect can be explained by defect migration processes occurring in ultrasonic fields. The inter-ion charge exchange, termed as acoustically-stimulated chemical reaction, is furthermore suggested to occur affecting the defect migration. This new method of a cold annealing of radiation defects in solids can be regarded as nanoacoustic defect manipulation.

The Journal of the Acoustical Society of America, 2020

The optical experiments with suspended quartz crystals reflecting Laser-Doppler-Vibrometer (LDV) ... more The optical experiments with suspended quartz crystals reflecting Laser-Doppler-Vibrometer (LDV) beam reveal an effect of crystal pendulum vibrations initiated by Sun's radiation of heavy particles. The LDV measures speed S(t) of oscillating crystal surface. The Fourier-transform of S(t) returns a spectrum of the acoustic vibrations with a few hertz frequency. The S(t) is a sine-type curve with amplitude depending on the time and space orientation of crystal axes. Maximum vibrational speed and corresponding crystal displacement from a position of equilibrium are observed when quartz piezoelectric axis is aimed toward the Sun. Experimental evidences exclude involvement of any electro-magnetic wave. The theoretical calculations for an oscillator driven by a periodic pulse-force are compared to the experimentally detected oscillations. The computations give a work done by an external force to move the crystal from its equilibrium to maximum displacement. It yields a mass of a think...

Journal of Physical Studies, 1998

A new acousto-electrical method making use of transient transverse acoustoelectric voltage (TAV) ... more A new acousto-electrical method making use of transient transverse acoustoelectric voltage (TAV) to study solid state structures is reported. This voltage arises after a surface acoustic wave (SAW) generating the signal is switched off. Related measurements consist in detecting the shape of transient voltage and its spectral and temperature dependence. Both theory and experiment show that this method is an effective tool to characterize trapping centers in the bulk as well as at surfaces or interfaces of epitaxial semiconductor structures.

Proceedings of Meetings on Acoustics, 2018

The new kind of experiments involving free vibrating crystal and space orientation of its crystal... more The new kind of experiments involving free vibrating crystal and space orientation of its crystallographic axes with respect to the stars are presented. The discovered "crystal-star effect" consists of changes in the vibrating crystal under the influence of cosmic radiation. It allows direct detection of the dark matter. The crystal-star nonclassical nonlinearity is demonstrated by measuring radio-frequency admittance, Y(F), from the quartz resonators near frequency F=10 MHz. The dark particles of (4+-1.5)x10E15 eV are directly detected, this energy corresponds to dark matter candidates Q-balls. The measured speed of particles in space is (249+-1.5) km/sec. One may call revealed particles "navitens" as they are energetic, invisible/unknown in experimental astronomy and high-energy physics. The changes in Y(F) are observed when specific crystallographic axis is directed toward the Sun, or Milky Way center, or star Deneb. The navitens may transfer their energy and linear momentum to a media of propagation. The independent test with a video camera captures the rocking-type motion of some samples under the influence of these particles. The navitens may create the micro-voids and tracks in a vibrating transparent dielectric. The physics of the crystal-star effect may be associated with the gravitational and quantum properties of the detected particles.

Proceedings of Meetings on Acoustics, 2018

The point defects in the spectra of photoluminescence of Lithium niobate (LN) and Lithium tantala... more The point defects in the spectra of photoluminescence of Lithium niobate (LN) and Lithium tantalate (LT) can be categorized as noble gases, heavy metals, and others. The distribution of charged defects (DCD) reveals peaks and valleys in a direction perpendicular to the z-axis, in both single crystals (SC) and periodically poled (PP) crystals. The distance between consecutive peaks and valleys equals the length of a ferroelectric domain in PPLT. The position of the ferroelectric domain wall with respect to point defects extrema is different in PPLT in comparison to PPLN. The DCD influences acousto-electric properties including electromechanical transduction (EMT) and electromechanical coupling coefficient (ECC), in a direction perpendicular to the z-axis. The results may be used to explain nonclassical nonlinearity in LN and LT crystals.

Acta Universitaria, 2005

Optical spectra of light reflection are detected under an influence of ultrasonic wave (UW)on a G... more Optical spectra of light reflection are detected under an influence of ultrasonic wave (UW)on a GaAs wafer. The differential spectrum is calculated as a difference between those taken under UW and without that influence on a sample. This acousto-optic differential reflectance(AODR) spectrum contains some bands that represent the energetic levels of the shallow centers in a sample. A physical basis of this technique is related to a perturbation of local states by UW. Here, a method is developed for characterization of local states at the surfaces and interfaces in crystals and low-dimensional epitaxial structures based on microelectronics materials. A theoretical model is presented to explain AODR spectra. Also, experiments using epitaxial GaAs structures doped by Te were made. Finally, theoretical and experimental results show that acousto-optic reflectance is an effective tool for characterization of shallow trapping centers in epitaxial semiconductor structures.

The Journal of the Acoustical Society of America, 2017

The photoluminescence (PL) from point defects in ferroelectric phononic crystal (FPC) is investig... more The photoluminescence (PL) from point defects in ferroelectric phononic crystal (FPC) is investigated at room temperature. The FPC consists of periodically poled domains 0.45-mm-long each along the x-axis in the 0.5-mm-thick z-cut LiNbO3 wafer. The spectra of PL are excited by 310 nm ultraviolet light and registered in the range of 350 to 900 nm. The PL spectra reveal different point defects including F-center, Ba, Ar, Ne, Cr, K, Fe+, Xe, and others. The electrically active defects such as F-center and Fe+ are expected to be sensitive on a local electric polarization. In a FPC, the ferroelectric neighboring domains are inversely poled and have an opposite electric polarization. The change from polarization “up” to polarization “down” happens across so called interdomain wall. The point defect concentrations along the neighboring domains are researched by PL-scanning, consisting of taking PL-spectra from narrow zones across the domain structure along the x-axis. This scanning reveal a nonuniform distributi...

Journal of the Acoustical Society of America, 2016

Nonclassical nonlinearity (NN) in ultrasound attenuation and acoustic memory in LiNbO3.may be con... more Nonclassical nonlinearity (NN) in ultrasound attenuation and acoustic memory in LiNbO3.may be connected to crystal defects. The optical spectra of photoluminescence (PL) and absorption taken from 350—900 nm reveal multiple point defects and impurities such as F-center, NbLi+, Fe, Ba, Ar, Xe and others. The spectra are taken at room temperature from the Czochralski grown bulk crystals and wafers. The samples are scanned by taking PL spectra from different locations along the z- and y-axes. The data from several samples reveal a nonuniform distribution of the defects along the crystallographic axes. The dependencies of PL peaks versus position have a sine-like component on top of some constant intensity. For instance, a scan for F-center has a period (P) from 0.27 to 0.75 mm and for Ba impurity from 0.25 to 0.75 mm in bulk crystals. In the wafers, P may be smaller, that is 0.1 mm and smaller. However, a ratio of maxima to minima in PL peaks is higher for bigger P. The overall spread o...

Journal of the Acoustical Society of America, 2016

The vibrations and matching acousto-electric resonances in 3-D periodically poled LiNbO3 bar are ... more The vibrations and matching acousto-electric resonances in 3-D periodically poled LiNbO3 bar are investigated. Two superlattices are fabricated in the z-cut 0.5-mm-thick wafers. They consist of the inversely poled domains of 0.45- or 0.3-mm long along the x-axis and tens-mm wide along the y-axis. Metal electrodes are deposited at the ends of superlattices along the x-axis. Experimentally, the vibrations are excited in MHz frequency range by the electric current along the x-axis or acoustic burst propagating along this axis. The function generator, digital oscilloscope, and spectrum analyzer allow measuring frequency dependencies of the acousto-electric resonances in rf-admittance Y(f), and transmission coefficient for acoustic burst propagating through the superlattice. The finite element method computations yield the acoustic displacements and acousto-electric admittance versus frequency. The displacements have three components along the x, y, and z axes. They are minimized within ...

Journal of the Acoustical Society of America, 2016

The observation of a nonstructural acousto-injection luminescence (NAIL) from metallized LiNbO3 w... more The observation of a nonstructural acousto-injection luminescence (NAIL) from metallized LiNbO3 wafers is reported. The X- and Y-cut plates with linear dimensions of a few mm and silver paste electrodes on opposite surfaces are investigated. The experiments are done at room temperature. The fundamental shear modes are excited at MHz-frequencies. We measure the spectra of NAIL, acousto-electric resonance/antiresonance properties, X-ray diffraction rocking curves, acoustic emission accompanying NAIL, and photoluminescence. The NAIL and associated effects appear above a certain threshold acoustical strain of e = 10-5. The results are explained in the terms of considerable piezoelectric fields, yielding the charge injection from the metal contacts into crystal along with the strong mechanical stresses leading to dislocations motion. The acoustic emission and X-Ray rocking curves disclose the dislocation motion under e > 10-5. The involvement of the microstructural non-uniformities in...

The Journal of the Acoustical Society of America, 2014

The acoustical transduction in an array of ferroelectric domains with alternating piezoelectric c... more The acoustical transduction in an array of ferroelectric domains with alternating piezoelectric coefficients is characterized by multi-frequency resonances, which occur at the boundary of the acoustic Brillouin zone (ABZ). The resonances correspond to two successive domain excitations in the first and second ABZ correspondingly, where the speed of ultrasound is somewhat different. An important parameter for acoustical transduction is the electric impedance Z. The results of the theoretical and experimental investigations of Z in a periodically poled LiNbO3 are presented. The magnitude and phase of Z depend on the array parameters including domain resonance frequency and domain number; Z of arrays consisting of up to 88 0.45-mm-long domains in the zx-cut crystal are investigated. The strong changes in Z-magnitude and phase are observed in the range of 3–4 MHz. The two resonance zones are within 3.33 ± 0.05 MHz and 3.67± 0.05 MHz. The change in domain number influences Z and its phase...

The periodically poled ferroelectric wafer is a two-dimensional phononic superlattice. The import... more The periodically poled ferroelectric wafer is a two-dimensional phononic superlattice. The important applications of such a solid include novel ultrasonic transducers at the micro/nano-scale for low intensity ultra-sonography, ferroelectric data storage, and development of very high frequency chips for next generation communication and information technologies, and others. Usually, the transformations between the electrical and mechanical energies are required in the applications. In this work, we find the frequency characteristics for an effective acousto-electric interaction in a two-dimensional phononic superlattice inserted in LiNbO3 wafer.

Fabrication of the bimorph lithium niobate cantilevers involves a micro machining of a z-cut wafe... more Fabrication of the bimorph lithium niobate cantilevers involves a micro machining of a z-cut wafer to create a multidomain structure. After etching, the bimorph ferroelectric cantilevers are fabricated at the locations near interdomain walls. Cantilever vibrations are excited by rf voltage due to piezoelectric effect in a ferroelectric chip, and optical detection is employed to pickup the vibrations. The self-assembling layers of two different Silanes are chemically deposited on the micro cantilevers. The layers are detected independently by two methods including a low frequency shift of cantilever natural vibrations, and Raman spectral lines from the Silane layers. Possible applications include smart biosensors in a real time domain.