In this work, the experimental realization of hybrid SAW/BAW resonators based on AlN thin films on Si(111) substrates with sub micrometre wavelengths are reported. Methods of having both main propagating modes of the hybrid SAW/BAW being located outside the cut-off region, where the velocity of the propagating wave surpasses the velocity of leaky substrate waves, leading to suppression of high velocity modes, are discussed using FEM simulations, which are then investigated experimentally. Concept verification was carried out using electron-beam lithography (EBL) in combination with dry etching of the top electrode and the AlN thin film.

This paper presents a piezoelectric RF MEMS resonator based on Lamé-mode excitation in an AlScN piezoelectric film deposited on silicon substrate. The fabricated devices exhibit an effective electromechanical coupling coefficient of 14% and an antiresonance quality factor of 494 at 1.75 GHz. Several design configurations were implemented to suppress spurious modes. The proposed device is promising for applications in 5G telecommunication systems.

This paper presents experimental results on the influence of geometric parameters on the performance of AlScN based solidly mounted Lamé mode resonators. Different device configurations, based on sets of design variables such as the wavelength, the metallization ratio and the number of the interdigitated transducers (IDTs) as well as the aperture were investigated. Their effect on performance metrics, being the electromechanical coupling, quality factor and the shape of the frequency response are demonstrated at wafer-scale in order to assess device uniformity, providing guidelines for optimal device design and fabrication.

This paper presents the simulation and experimental results of a solidly mounted Lame mode resonator based on AlScN piezoelectric thin films. The devices were fabricated in two configurations: with the AlScN film deposited on a Mo/SiO2/Si substrate and on a multilayered acoustic Bragg mirror. The resonators demonstrated outstanding performance, achieving an electromechanical coupling coefficient of 14.3% and a quality factor of 1110 at 1718 MHz. The highest experimental coupling coefficient reached 18%.

SAW and BAW resonators can be used in highprecision applications such as sensing and frequency control, where temperature-induced frequency shifts can significantly affect performance. In this work, a hybrid SAW-BAW resonator using aluminum nitride thin films as the piezoelectric material is introduced, utilizing two involved frequency modes to achieve temperature compensation for one resonant mode while enhancing the temperature sensitivity of another.

Pseudobinary nitride alloys display enhanced piezoelectric properties compared to their nonalloyed counterparts enabling their wide application in high‐performance transducers and acoustic wave resonators. Their fabrication remains challenging because of their inherently stochastic nature, which requires in‐depth understanding of the film growth dynamics and the interplay of deposition parameters. Herein, thin Al 1− x Y x N films are produced with varied yttrium content in the range from x = 0.09 to 0.28 on a gradient seed layer on 200‐mm Si substrates and investigated via various X‐ray diffraction methods, high‐resolution scanning transmission electron microscopy, nanoindentation, and atomic force microscopy. Bulk acoustic wave resonators, solidly mounted on a multilayer acoustic isolation, are fabricated to analyze the piezoelectric performance of the films and to extract corresponding material parameters via fitting of the high‐frequency electrical response by 1D Mason's model. The trend of declining coupling is explained by the lattice softening and the increase in electron density, experimentally observed by monitoring reduced elastic modulus and dielectric constant values, respectively. The absence of expected enhancement of the piezoelectric modulus is interpreted by the presence of oxygen impurities, facilitating the inhomogeneous strain of the AlYN lattice, which effectively cancels the energy flattening phenomenon, found in III–V pseudobinary alloys.

Nowadays, there is an urgent issue in creating highly sensitive current, magnetic field, temperature, and pressure sensors. For this purpose, a magnetic La0.6Sr0.3Mn1.1O3 (LSMO) nanopowder has been synthesized by atomization hydrolysis and compacted under different pressures up to 1600 MPa. Their phase compo-sition, crystal structure, morphology, magnetic, magneto-resonance, transport, magnetoresistance (MR), and baroresistance (BR) properties have been comprehensively studied. It has been shown that the LSMO nanopowder is a single-phase perovskite and consists of spherical-like particles with an average size of 37 nm. As the pressure increases to 1600 MPa, the filling factor in the compacts increases, decreasing the average distance between particles. In the room temperature range, the LSMO nanopowder is in a ferro-magnetic state with a Curie temperature TC = 367 K and does not depend on the compacting pressure P. The conductivity is thermally activated by hopping conduction along the nearest particles. With increasing P, a monotonic decrease in resistivity is due to reducing the distance between particles. The temperature de-pendences of the MR have a tunneling character. Giant BR effect with the establishment of the following important applied properties has been found: (i) the BR effect is not limited by the Curie temperature and is observed both in the ferromagnetic and paramagnetic states; (ii) the BR effect under constant pressure slightly depends on the temperature in a wide range from - 193 to + 127 celcius; (iii) in the pressure range from 0 to 400 MPa, the BR effect has the highest sensitivity of 0.1%/MPa. The obtained results and established regularities in the LSMO nanopowder compacts can be used to create pressure sensors for modern in-telligent process control systems.(c) 2022 Elsevier B.V. All rights reserved.

The magnetic susceptibility χ of RMnO3 (R = La, Y) manganites was measured for paramagnetic phase as a function of the hydrostatic pressure P up to 2 kbar at some fixed temperature in the range from 78 to 300 K. A pronounced magnitude of the pressure effect dln χ/dP was found to be positive in sign for LaMnO3 and negative for YMnO3, both being strongly temperature dependent. Analysis of the experimental data, based on the Curie-Weiss behavior of χ(Τ), allowed to estimate the pressure derivative of the paramagnetic Curie temperature to be dΘ/dP = (0.25 ± 0.03) and −(2.4 ± 0.4) K/kbar for LaMnO3 and YMnO3, respectively.

Using the method of SQUID magnetometry, the features of the antiferromagnet-ferromagnet thermomagnetic transition in arrays of the nanosized disks of Py/NiCu/Py synthetic antiferromagnets (SAFs) have been investigated. The effective interlayer interaction in individual SAFs "ferromagnet/diluted ferromagnet/ferromagnet" (F2/f/F1) changes from high-temperature antiferromagnetic to low-temperature ferromagnetic upon the transition at the Curie temperature T-C(f) of the interlayer f. Temperature dependence of the magnetic parameters of individual layers and their effect on the features of the thermomagnetic transition are determined. The observed properties are important for the development of temperature-controlled nanoscale SAFs and multilayer nanostructures based on them.

Due to their enhanced piezoelectric coefficient, aluminum scandium nitride thin films have been a promising piezoelectric material for MEMS, in particular for RF filters applications. Resonators based on this material present strong microfabrication challenges, especially in applications where partial etching of the piezoelectric AlScN is necessary, such as hybrid SAW/BAW devices. This work compares different AlScN etching techniques, with the aim of achieving smooth fully or partially etched surfaces, nearly vertical sidewalls, and high selectivity towards the mask material.

Using battery less sensor module to monitor the environmental condition inside the metal pipes is one of the highly demanding and challenging research topics in industry. In this paper a flexible ultrasonic transducer by application of 12 (3X4) thinned piezoceramics with the thickness of 195 μm has been proposed for RF-Data and energy transmission through the metal pipe with the thickness of 1 cm. The main idea is utilizing near field communication (NFC) technology with center frequency of 13.56 MHz by replacement of RF-antenna with array of PZTs to monitor the internal condition of the metal pipe in the detachable method. By application of the proposed flexible transducer, it is possible to transmit 60 mW energy from detachable NFC-reader to the transponder side which is placed in the non-accessible side of metal pipe. Additionally, the process flow of fabrication of flexible array of 3X4 piezoceramic is presented. According to the simulation and experimental results, the power transmission efficiency has been enhanced by 3 % and the bandwidth is extended by 80 %.

The variation of the Bi 1 – x Y x FeO 3 ceramics atomic structure with yttrium concentration x = 0, 0.10, 0.15, and 0.20 has been analyzed. Ceramic samples have been prepared by rapid sintering using a normal solid-phase reaction. X-ray diffraction data for Bi 1 – x Y x FeO 3 samples show that the rhombohedric-to-orthorhombic concentration phase transition takes place at x = 0.2 with an inflection point at x = 0.15. It has been found that the permittivity and dielectric loss tangent of the samples gradually decrease with rising yttrium content.

The experimental studies of the paramagnetic-antiferromagnetic phase transition through Mössbauer spectroscopy and measurements of temperature and field dependencies of magnetic susceptibility in the layered Cu0.15Fe0.85PS3 crystal are presented. The peculiar behavior of the magnetization - field dependence at low-temperature region gives evidence of a weak ferromagnetism in the studied alloy. By the ab initio simulation of electronic and spin subsystems, in the framework of electron density functional theory, the peculiarities of spin ordering at low temperature as well as changes in interatomic interactions in the vicinity of the Cu substitutional atoms are analyzed. The calculated components of the electric field gradient tensor and asymmetry parameter for Fe ions are close to the ones found from Mössbauer spectra values. The Mulliken populations show that the main contribution to the ferromagnetic spin density is originated from 3d-copper and 3p-sulfur orbitals. The estimated total magnetic moment of the unit cell (8.543 emu/mol) is in reasonable agreement with the measured experimental value of ∼9 emu/mol.

This work reports on the growth of 1 µm nonpolar a-plane Al0.7Sc0.3N(112¯0) thin films on an r-plane sapphire Al2O3(11¯02) via magnetron sputter epitaxy. The electro-acoustic properties of the film structures were characterized using surface acoustic wave (SAW) resonators. Measured electrical responses were found to be strongly anisotropic in terms of the wave propagation direction. We identified a sagittal polarized Rayleigh wave mode with large coupling (keff2= 3.7%), increased phase velocity (v= 4825 m/s), as well as high quality factor (Q > 1000) for SAW propagation along the c-axis [0001] and normalized thicknesses h/λ=0.2. Finite element method simulations using electro-acoustic properties of Al0.7Sc0.3N obtained from the density functional theory reproduce our experimental results.

In this paper we demonstrate the possibility of “through-wall” temperature measurement via the acoustically coupled PZT transducers operated at the frequency of 12 MHz. Temperature measurement was done by thermistor attached to hotplate and electrically connected via the matching network to the PZT transducer. Temperature dependent electrical impedance variation of PZT on the one side of the wall leads to changing of the reflection coefficient S 11 on the PZT transduce from other side of the metal wall and can be easily detected by the network analyzer.

Prospects for the use of manganites in various areas of modern technologies require comprehensive studies of their physical and chemical properties. La 0.9 Mn 1.1 O 3 (LMO) ceramics were synthesized at annealing temperature t ann = 1150 ℃ with further post-annealing at 1250, 1350, and 1450 ℃. They have been studied comprehensively using XRD, SEM, EDS, thermogravimetric, magnetic under high pressure, and electrochemical methods. As the t ann increases, the crystal structure symmetry changes from the rhombohedral R -3 c to the monoclinic P 21/ c type, the crystallite size and concentration of chemical defects increase, and the tolerance factor reduces. The post-annealing, on one hand, leads to a dramatic reduction of the magnetic entropy change –Δ S M max from 3.50 to 0.75 J/(kg⋅K) under 2 T and Curie temperature T C from 227 to 113 K with an increase in the t ann . This is due to the weakening of both the double-exchange (DE) and multiple DE interactions by the increased content of chemical defects. On the other hand, an external hydrostatic pressure works oppositely enhancing DE interactions and reducing the disorder. The saturation of the –Δ S M max and T C is achieved already at around 0.4 GPa. The LMO-1150 exhibits the best magnetocaloric characteristics to compare with other studied samples. Moreover, the electrochemical characteristics of the LMO materials as electrocatalysts for overall water splitting (OER process) and features of their transformation in different 0.5 M K 2 SO 4 , 0.5 M K 2 HPO 4 , and 0.1 M K 2 B 4 O 7 electrolytes have been studied thoroughly. After electrocatalysis, the magnetization M decreases and the T C remains the same indicating the persistence of the DE. All samples show the best electrochemical performance in the 0.5 M K 2 HPO 4 media. The obtained results demonstrate the ways for controlling magnetocaloric parameters of the LMO ceramics at changing the internal and external conditions, as well as an evaluation of the possibilities for their OER applications in electrocatalysts.

Nowadays, there is an urgent issue in the creation of highly sensitive current, magnetic field, temperature, and pressure sensors. For this purpose, a magnetic La0.6Sr0.3Mn1.1O3 (LSMO) nanopowder has been synthesized by atomization hydrolysis and compacted under different pressures up to 1600 MPa. Their phase composition, crystal structure, morphology, magnetic, magneto-resonance, transport, magnetoresistance, and baroresistance properties have been comprehensively studied. It has been shown that the LSMO nanopowder is a single-phase perovskite and consists of spherical-like particles with an average size of 37 nm. As the pressure increases to 1600 MPa, the filling factor in the compacts increases, decreasing the average distance between particles. In the room temperature range, the LSMO nanopowder is in a ferromagnetic state with a Curie temperature TC = 367 K and does not depend on the compacting pressure P. The conductivity has a thermally activated nature of hopping conduction along the nearest particles. With increasing P, a monotonic decrease in resistivity is due to reducing the distance between particles. The temperature dependences of the magnetoresistance have a tunneling character. Giant baroresistance effect with the establishment of the following important applied properties has been found: (i) the baroresistance effect is not limited by the Curie temperature and is observed both in the ferromagnetic and paramagnetic states; (ii) the baroresistance effect under constant pressure slightly depends on the temperature in a wide range from –193 to +127 °C; (iii) in the pressure range from 0 to 400 MPa, the baroresistance effect has the highest sensitivity of 0.14%/MPa. The obtained results and established regularities in the LSMO nanopowder compacts can be used to create pressure sensors for modern intelligent process control systems.

This work reports on the growth of 1 mu m nonpolar a-plane Al0.7Sc0.3N(1120) thin films on an r-plane sapphire Al2O3(1102) via magnetron sputter epitaxy. The electro-acoustic properties of the film structures were characterized using surface acoustic wave (SAW) resonators. Measured electrical responses were found to be strongly anisotropic in terms of the wave propagation direction. We identified a sagittal polarized Rayleigh wave mode with large coupling (k(eff)(2) = 3.7%), increased phase velocity (v = 4825 m/s), as well as high quality factor (Q> 1000) for SAW propagation along the c-axis [0001] and normalized thicknesses h/lambda= 0.2. Finite element method simulations using electro-acoustic properties of Al0.7Sc0.3N obtained from the density functional theory reproduce our experimental results. (C) 2022 Author(s).

Data and energy transmission through the metal barriers enable us to monitor the environmental condition in the not accessible side of the metal chambers. In this study, near field communication (NFC) technology has been utilized for energy harvesting and data communication by replacement of RF antenna with ceramic PZTs. The main concept is based on energy and data transmission with ultrasonic wave by application of direct and indirect effect of piezoelectric. Due to the comb-resonance effect of metal barriers which has a dominant effect on the communication, a method is proposed to reduce the fluctuation and flatten the bandwidth in the designated frequency range (13.56 MHz). Additionally, detachable method of communication on the reader side by study on couplant material and a method for alignment of reader and transponder is discussed, in this paper. For the experimental investigation, 200 um-thick, 5mm-diameter disc PZTs have been utilized as the ultrasonic transducers of the communication system. Based on experimental results, 30mW energy could be harvested by means of NFC ICs to supply the sensor modules with integrated ADC which are used on the not accessible side of metal chamber.

The magnetic properties of thin-film multilayers [Fe/Py]/FeMn/Py are investigated as a function of temperature and thickness of the antiferromagnetic FeMn spacer using SQUID magnetometry. The observed behavior differs substantially for the structures with 6 nm and 15 nm FeMn spacers. While the 15 nm FeMn structure exhibits exchange pinning of both ferromagnetic layers in the entire measurement temperature interval from 5 to 300 K, the 6 nm FeMn structure becomes exchange de-pinned in the vicinity of room temperature. The depinned state is characterized by a single hysteresis loop centered at zero field and having enhanced magnetic coercivity. The observed properties are explained in terms of finite-size effects and possible ferromagnetic interlayer coupling through the thin antiferromagnetic spacer.