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The ordered Ca3TaGa3Si2O14 and disordered La3Ga5SiO14 crystals of the lantangallium silicate family were grown via the Czochralski method. The independent coefficients of thermal expansion of crystals αc and αa were determined using X-ray powder diffraction based on the analysis of X-ray diffraction spectra measured in the temperature range of 25~1000 °C. It is shown that, in the temperature range of 25~800 °C, the thermal expansion coefficients are linear. At temperatures above 800 °C, there is a nonlinear character of the thermal expansion coefficients, associated with a decrease in the Ga content in the crystal lattice.

The ordered Ca3TaGa3Si2O14 and disordered La3Ga5SiO14 crystals of the lantangallium silicate family were grown by the Czochralski method. The independent coefficients of thermal expansion of crystals αc and αa were determined by X-ray powder diffraction based on the analysis of X-ray diffraction spectra measured in the temperature range of 25÷1000°C. It is shown that in the temperature range of 25÷800°C the thermal expansion coefficients are linear. At temperatures above 800°C there is a nonlinear character of the thermal expansion coefficients associated with a decrease in the Ga content in the crystal lattice of the lantangallium silicate family crystals.

Lithium niobate and lithium tantalate are among the most important and most widely used materials in acousto-optics and acoustoelectronics. These materials have high values of piezoelectric constants, which makes it possible to use these materials as actuators; however, their use is limited by the thermal instability of a lithium niobate crystal and the low Curie temperature (TC) of a lithium tantalate crystal. LiNb(1-x)TaxO3 crystals have to overcome the aforementioned limitations of individual compounds.Crystals LiNb0.5Ta0.5O3 were grown by the Czochralski method, of good quality. Comparative studies of the features of high-temperature single domainization of LiNb0.5Ta0.5O3 crystals have been carried out. The main differences in the technological regimes for single-domainization of congruent LiNb0.5Ta0.5O3 crystals from congruent LiNbO3 crystals are demonstrated. The parameters of high-temperature electrodiffusion processing LiNb0.5Ta0.5O3 crystals are presented, which make it possible to obtain single-domain crystals for further study of their physical properties.

Lithium niobate and tantalate are among the most important and widely used materials of acoustooptics and acoustoelectronics. They have high piezoelectric constants enabling their use as actuators. Their use is however restricted by the thermal instability of lithium niobate crystals and the low Curie temperature TC of lithium tantalate crystals. Overcoming these drawbacks typical of some compounds is possible by growing LiNb1-xTaxO3 single crystals. Good quality LiNb1-xTaxO3 single crystals have been grown using the Czochralsky technique. High-temperature poling process of LiNb1-xTaxO3 single crystals has been studied. The main differences between the process modes required for poling of congruent LiNb1-xTaxO3 single crystals and congruent LiNbO3 single crystals have been demonstrated. Parameters of high-temperature electric diffusion processing of LiNb1-xTaxO3 single crystals that provide for singledomain crystals for further study of physical properties have been reported.

Ferroelectric LiNb1–x Ta x O3 solid solutions with various Nb/Ta ratio were grown from the melt by the Czochralski method. The exact composition of the grown crystals was determined by inductively coupled plasma atomic mass spectrometry. The dependence of the crystal composition on the composition of the initial melt was obtained and explained by a wide separation between the phase boundaries of the liquid and solid phases on the LiNbO3–LiTaO3 phase diagram. Using high-resolution X-ray diffraction, the parameters a and c of a crystal unit cell were determined (LiNb0.88Ta0.12O3: a = 5.1574 Å and c = 13.8498 Å). Further, the Curie temperature T C of the crystals was measured using the differential scanning calorimetry technique. T C was found to depend on the composition of the crystals that allowed conditions for the monodomainization of the grown crystals to be defined (LiNb0.88Ta0.12O3: T C = 1102°C; LiNb0.33Ta0.67O3: T C = 794°C). Finally, the velocity of surface acoustic waves was determined by scanning electron microscopy and X-ray diffraction techniques (YZ-cut of a LiNb0.88Ta0.12O3 crystal: V = 3440 m s−1).

In this Letter, we studied the photoresponse in multilayer graphene on a lithium niobate (LiNbO3) crystal under the conditions of an electric potential applied to graphene and transmission of a surface acoustic wave. The acoustoelectric current in graphene when irradiated with light is shown to either increase or decrease depending on the polarity of the potential applied to graphene. A surface acoustic wave causes the appearance of a periodic charge lattice in graphene that enhances the interaction with incident light, which leads to an increase in the photoresponse.

We present a novel method of temporal modulation of X-ray radiation for time resolved experiments. To control the intensity of the X-ray beam, the Bragg reflection of a piezoelectric crystal is modified using comb-shaped electrodes deposited on the crystal surface. Voltage applied to the electrodes induces a periodic deformation of the crystal that acts as a diffraction grating, splitting the original Bragg reflection into several satellites. A pulse of X-rays can be created by rapidly switching the voltage on and off. In our prototype device the duty cycle was limited to ∼1 ns by the driving electronics. The prototype can be used to generate X-ray pulses from a continuous source. It can also be electrically correlated to a synchrotron light source and be activated to transmit only selected synchrotron pulses. Since the device operates in a non-resonant mode, different activation patterns and pulse durations can be achieved.

X-ray diffuse scattering from the Ca3NbGa3Si2O14 (CNGS) crystal was measured with a triple axis X-ray diffractometer under the conditions of an external electric field. It is found that the nature of the intensity distribution of the asymmetrical part of diffuse scattering depends on the value of the applied electric field. This phenomenon is apparently associated with different piezoelectric characteristics of defect regions and the rest of the single crystal.

Because of their unique atomic structure, 2D materials are able to create an up-to-date paradigm in fundamental science and technology on the way to engineering the band structure and electronic properties of materials on the nanoscale. One of the simplest methods along this path is the superposition of several 2D nanomaterials while simultaneously specifying the twist angle between adjacent layers (θ), which leads to the emergence of Moire superlattices. The key challenge in 2D nanoelectronics is to obtain a nanomaterial with numerous Moire superlattices in addition to a high carrier mobility in a stable and easy-to-fabricate material. Here, we demonstrate the possibility of synthesizing twisted multilayer graphene (tMLG) with a number of monolayers NL = 40-250 and predefined narrow ranges of θ = 3-8°, θ = 11-15°, and θ = 26-30°. A 2D nature of the electron transport is observed in the tMLG, and its carrier mobilities are close to those of twisted bilayer graphene (tBLG) (with θ = 30°) between h-BN layers. We demonstrate an undoubtful presence of numerous Moire superlattices simultaneously throughout the entire tMLG thickness, while the periods of these superlattices are rather close to each other. This offers a challenge of producing a next generation of devices for nanoelectronics, twistronics, and neuromorphic computing for large data applications.

The effect of photon annealing on deformation in the crystal structure of boron doped Cz-Si wafers has been studied using triple crystal X-ray diffraction. Conventional annealing of the entire surface of double-side polished silicon wafers with halogen lamps (photon annealing mode) and rapid thermal annealing produce compression deformation. Annealing with special phototemplate providing for local annealing of multiple separated wafer areas (local photon annealing mode) at relatively low wafer temperatures (less than 55 °C) produces tensile deformation. This effect however is not observed if the reverse side of the annealed wafer contains a mechanical gettering layer. A mechanism explaining the experimental results has been suggested and can be used for the synthesis of charge pumps in photoelectric converter structures.

We report a simple and efficient deposition technique for the growth of highly-textured AlN thin films. The proposed chloride-based chemical vapor deposition approach is based on widely available precursors and an unsophisticated experimental set-up. The films were characterized by electron microscopy, X-ray diffraction, Raman spectroscopy and cathodoluminescence. We studied the correlations between the deposition conditions and the properties of the resulting films, such as morphology, microstructure, features of the Raman spectra, and piezoelectric characteristics. In particular, we show that the minimum of the Raman bands A1(TO)/ E2(h) intensity ratio, under excitation along c-axis, corresponds to the maximum of the piezoelectric coefficient. The films deposited under the optimized conditions are composed of well-aligned column-like crystallites. These films have a piezoelectric coefficient of 5.5–6.5 pC/N, which approaches the highest values reported for this material. The simplicity, efficiency and high quality of the resulting films make the proposed deposition approach highly interesting for a wide range of practical applications.

This work presents the experimental investigation of the synthesis of graphene carbon nanocomposites (CNC-G) by carbonization of porous silicon (PS) using CVD method at low temperature of T = 350–500 °C. The low-temperature synthesis of CNC-G is explained by a low melting temperature of porous silicon nanocrystallites (nc-PS) formed during electrochemical etching.

Electrical conductivity and acoustic loss Q−1 of single crystalline Li(Nb,Ta)O3 solid solutions (LNT) are studied as a function of temperature by means of impedance spectroscopy and resonant piezoelectric spectroscopy, respectively. For this purpose, bulk acoustic wave resonators with two different Nb/Ta ratios are investigated. The obtained results are compared to those previously reported for congruent LiNbO3. The temperature dependent electrical conductivity of LNT and LiNbO3 show similar behavior in air at high temperatures from 400 to 700 °C. Therefore, it is concluded that the dominant transport mechanism in LNT is the same as in LN, which is the Li transport via Li vacancies. Further, it is shown that losses in LNT strongly increase above about 500 °C, which is interpreted to originate from conductivity-related relaxation mechanism. Finally, it is shown that LNT bulk acoustic resonators exhibit significantly lower loss, comparing to that of LiNbO3.

The possibilities are presented of X-ray diffraction methods for studying the propagation of surface acoustic waves (SAWs) in solids, including diffraction under total external reflection conditions and Bragg diffraction, using acoustically modulated X-ray multilayer mirrors and crystals. SAW propagation was studied using both meridional and sagittal diffraction geometries where the SAW wavevectors and X-ray photons are collinear or perpendicular, respectively. SAW propagation in a crystal leads to sinusoidal modulation of the crystal lattice and the appearance of diffraction satellites on the rocking curve. The intensities and angular positions of these diffraction satellites are determined by the SAW wavelength, amplitude and attenuation. Therefore, diffraction methods allow the analysis of the SAW propagation process and determination of SAW parameters. The influence of X-ray energy on diffraction by acoustically modulated crystals is studied for the first time. It is shown that changes in the X-ray energy can change the angular region where diffraction satellites exist under conditions of total external reflection. By contrast, in the Bragg diffraction region changes in the X-ray photon energy lead to changes in the X-ray penetration depth into the crystal and redistribution of the diffracted intensity among diffraction satellites, but do not change the angular divergence between diffraction satellites on the rocking curve. It is also shown that, in X-ray diffraction on acoustically modulated crystals on a number of successive reflections, a decrease in interplanar spacing leads to an increase in the number of diffraction satellites and a redistribution of diffracted radiation between them.

Ferroelectric LiNb

In the present work, it is demonstrated for the first time that a simple, specially developed method for graphene oxide (GO) deposition on large areas opens the prospects of GO’s wide application in planar-group technologies for creating different electronic devices including memristor devices for neuromorphic computing systems in the field of large data and artificial intelligence. MOS structures based on synthesized large-area GO films were formed, and their switching characteristics were studied. Current-voltage measurements performed on the MOS capacitors demonstrated forming-less, device’s self-limited current behavior of GO bipolar resistive switching characteristics with the current density of up to 1 A/cm2. Multiple sharp transitions from the high resistance state to low resistance state in the pristine GO film under the DC voltage sweep may indicate formation of multiple conductive filaments that provide stable conductive paths between GO layers. It was found out that in our devices at least two resistive switching mechanisms may occur simultaneously, namely, filament formation and charge trapping/de-trapping, which is great advantages of GO over other materials. The observed effects are interpreted using a model explaining resistive switching in GO associated with the drift of functional groups and its impact on the resulting different sp3 and sp2 domains.

Results of measurements of independent piezoelectric moduli d 11 and d 14 in Ca3NbGa3Si2O14, La3Ga5.5Ta0.5O14 and La3Ga5SiO14, promising single crystals of the calcium gallogermanate structural type, are presented. The moduli were measured with a triple-axis X-ray diffractometer under an external electric field which causes changes in the interplanar distances due to the reverse piezoelectric effect. The results of the X-ray diffractometry measurements agree fairly well (within less than 10%) with the results obtained by different methods.

The influence of quantum well structure and growth temperature on a synthesized multilayer system composed of a five-layer InMnGaAs quantum well with an InGaAs buffer layer grown on semi-insulating (100)-oriented substrates prepared by low temperature molecular beam epitaxy was studied. The magnetization measurements using a superconducting quantum interference device indicated the existence of ferromagnetism with a Curie temperature above room temperature in the five-layer InGaMnAs quantum well structure with an InGaAs buffer layer in a GaAs matrix. X-ray diffraction and secondary ion mass spectroscopy measurements confirmed the second phase formation of ferromagnetic GaMn clusters. The ferromagnetism that exists in the five-layer of the InMnGaAs quantum well with the InGaAs buffer layer results from a superposition of the ferromagnetism of the low temperature region from the substitutional Mn ions into Ga sites or interstitial Mn ions as well as the presence of manganese ions dopant clusters such as GaMn clusters.

We have fabricated as-grown ZnO nanorods (NRs) and carbon-assisted NR arrays on semi-insulating (100)-oriented Si substrates. We compared the structural and luminescent properties of them. High-resolution transmission microscopy, field emission scanning electron microscopy, x-ray diffraction and energy-dispersive x-ray revealed that the as-grown ZnO NRs and carbon-assisted ZnO NRs were single crystals with a hexagonal wurtzite structure, and grew with a c-axis orientation perpendicular to the Si substrate. These measurements show that the carbon-assisted ZnO NRs were better synthesized vertically on an Si substrate compared to the as-grown ZnO NRs. Photoluminescence measurements showed that luminescence intensity of the carbon-assisted ZnO NRs was enhanced compared to the as-grown ZnO NRs. The enhanced luminescence intensity of the carbon-assisted ZnO demonstrates the possible improvement in the performance of photovoltaic nanodevices based on ZnO-like materials. This method can be applied to the fabrication of well-aligned ZnO NRs used widely in optoelectronic devices.

A novel method of silicon carbide growth on silicon substrates is proposed. The method makes use of carbon recoil atoms implantation from a layer of molecules of carbon-containing gas, adsorbed on a cooled silicon surface bombarded by argon ions. A silicon carbide film is formed on the surface of a Si(1 1 1) substrate after high-temperature annealing in vacuum. The film properties are studied by IR-spectroscopy, XRD, AFM and optical microscopy methods. The studies have shown that the proposed method enables the growth of single-crystalline SiC films on the Si crystal surface.

In this research, beam focusing in lithium niobate plate was studied for fundamental anti-symmetric (A0) and symmetric (S0) Lamb waves, and the shear-horizontal (SH0) wave of zero-order. Using the finite element method, appropriate configuration of the interdigital transducer with arc-like electrodes was modeled accounting for the anisotropy of the slowness curves and dispersion of the modes in the plate. Profiles of the focalized acoustic beams generated by the proposed transducer were theoretically analyzed. Based on the result of the analysis, relevant delay lines were fabricated and transfer functions (insertion loss) of the line were measured for SH0 wave in YX-lithium niobate plate. Using an electron scanning microscope, distribution of the electric fields of the same wave were visualized. The results of this study may be useful for hybrid devices and sensors combining nano and acoustoelectronic principles.

X-ray Bragg diffraction in sagittal geometry on a Y-cut langasite crystal (La3Ga5SiO14) modulated by Λ = 3 µm Rayleigh surface acoustic waves was studied at the BESSY II synchrotron radiation facility. The surface acoustic waves create a dynamical diffraction grating on the crystal surface, which can be used for space–time modulation of an X-ray beam., X-ray Bragg diffraction in sagittal geometry on a Y-cut langasite crystal (La3Ga5SiO14) modulated by Λ = 3 µm Rayleigh surface acoustic waves was studied at the BESSY II synchrotron radiation facility. Owing to the crystal lattice modulation by the surface acoustic wave diffraction, satellites appear. Their intensity and angular separation depend on the amplitude and wavelength of the ultrasonic superlattice. Experimental results are compared with the corresponding theoretical model that exploits the kinematical diffraction theory. This experiment shows that the propagation of the surface acoustic waves creates a dynamical diffraction grating on the crystal surface, and this can be used for space–time modulation of an X-ray beam.

The results of studying a two-dimensional X-ray focusing by an off-axis grazing incidence phase Fresnel zone plate on the laboratory X-ray source are presented. This optics enables obtaining a focal spot of ~2 µm on the laboratory X-ray source with a focusing efficiency of ~30% at a high signal/noise ratio.

We investigated the peculiarities of the combustion wave propagation as well as the structure and phase formation in bi-layered metal powder compacts of (Ti − Al)/(Ni − Al), with a special emphasis on the use of infrared thermography to monitor the reaction front propagation. The location of the combustion wave front along the direction of propagation at different times was determined to calculate the front velocity. The data of SEM analysis demonstrated the welding of two layers during combustion with the formation of a transition layer with a thickness of about 200 μm and a sharp diffusion barrier for Ti in the Ni-Al layer.

Textured polycrystalline aluminum nitride films are grown on a silica substrate by chemical vapor deposition using metallic aluminum and ammonium chloride as the initial reagents. The good texture and crystal quality of the prepared films are confirmed by raster electron microscopy, Raman spectroscopy, and X-ray diffraction.

Fabrication of reduced graphene oxide/polyvinylidene fluoride (rGO/PVDF) membranes by coating the surface of standard polymeric PVDF membranes with thin graphene oxide (GO) film is demonstrated. rGO/PVDF membranes have a better filtration efficiency than standard polymer PVDF membranes. For stabilization of rGO/PVDF membranes, a pulsed photon annealing has been used. Increase of water flow through the rGO/PVDF membranes with the decrease of the nanochannel sizes has experimentally been shown. Water transportation via planar nanochannels of rGO membranes depends on an rGO reduction time, which is explained by a decrease of the water shear viscosity activation energy in nanochannels.

An erratum is presented to correct the typographical errors concerning the composition of the multilayer used in the experiment in Opt. Lett. 42, 1915.

We measured broad tunable spectra between 1.4 and 4.7 μm in the nonlinear crystal La3Ga5.5Ta0.5O14 (LGT). They were generated in the femtosecond regime from phase-matched difference frequency generation and optical parametric amplification.

Continuous polycrystalline zinc oxide films 5 to 15 μm in thickness have been produced on both single-crystal silicon and transparent amorphous glass substrates via the growth of aligned nanorod arrays by chemical vapor deposition followed by lateral growth of the nanorods. The growth of the lateral faces of the nanorods was carried out under specially adjusted conditions in the same reactor as was used to grow the nanorods. The resultant films consisted of intergrown columnar crystals oriented along the c axis of the ZnO lattice (perpendicular to the substrate surface). The cathodoluminescence spectrum of the films was dominated by excitonic emission in the near-UV spectral region. The films had high electrical conductivity (ρ = 0.45 Ω cm), due to excess zinc. Prolonged annealing in air increased the resistivity of the films by five orders of magnitude (to ρ = 6 × 104 Ω cm). According to X-ray diffraction and Raman spectroscopy data, the films had good structural perfection, comparable to that of zinc oxide nanorods.

The diffraction properties of phase gratings with the period D = 1.6, 1.0 and 0.5 µm fabricated on an Si(111) crystal by e-beam lithography were studied by triple-axis X-ray diffraction. A 100 nm-thick tungsten layer was used as a phase-shift layer. It is shown that the presence of a grating as a phase-shift W layer on the surface of the Si(111) crystal causes the formation of a complicated two-dimensional diffraction pattern related to the diffraction of X-rays on the phase grating at the X-ray entrance and exit from the crystal. A model of X-ray diffraction on the W phase diffraction grating is proposed.

Development and search for new advanced materials of the lanthanum gallium silicate group with unique thermal properties is of great importance for the development of acoustoelectronics based on volume and surface acoustic waves. The processes of surface acoustic wave excitation and propagation in the La3Ga5.3Ta0.5Al0.2O14 crystal was studied using a double-crystal X-ray diffractometer with a BESSY II synchrotron radiation source. The X-ray diffraction spectra of acoustically modulated crystals were used to measure the surface acoustic wave velocity and power flow angles in different acoustic cuts of the La3Ga5.3Ta0.5Al0.2O14 crystal.

We measured continuously tunable beams between 1.4 and 4.7 µm in the nonlinear crystal La3Ga5.5Ta0.5O14 (LGT) as predicted theoretically. They were generated in the femtosecond regime from difference frequency generation and optical parametric amplification.

A five-component crystal of lanthanum–gallium silicate group La3Ga5.3Ta0.5Al0.2O14 (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. The independent piezoelectric constants d 11 and d 14 were measured by X-ray diffraction in the Bragg and Laue geometries. Excitation and propagation of surface acoustic waves 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.

The results of the investigation of multicomponent piezoelectric crystals of the group of galliumlanthanum silicate (langasite) are presented. The synthesis processes and the structure of crystals are investigated. The acoustic properties of the crystals are investigated using X-ray topography and diffractometry. The possibility of applying these piezoelectric crystals in high-temperature sensor devices based on surface acoustic waves is shown.