As dielectric storage devices, dielectric membrane capacitors are widely used in various energy storage devices due to their high power density, medium energy density, and fast charging and discharging speeds. In this work, our team has grown high-quality and well-crystallized ferroelectric thin films xMn-BiMg 0.5 Ti 0.7 O 3 (xMn-BMT) on Pt/Ti/SiO 2 / Si (111) substrates by sol-gel method. The crystal lattice of xMn-BMT films is distorted by the addition of trace Mn elements, resulting in a grain size reduction, which is adjusted by oxygen vacancies and other factors. The ferroelectric properties of the film are affected, and hence the energy storage properties of the film. Finally, when the Mn doping amount is x (mol%)=3, a capacitor with excellent energy storage performance is obtained. Recycled energy storage has a density of up to 92.4 J/cm 3 and an energy storage efficiency of 74.8%. This work opens a new avenue for discovering high-energy density capacitors in dielectric memory thin films.
With employing judicious chemical modifications, two new isovalently substituted lead-free binary solid-solutions of 0.67BiFe 0.97-x Ga 0.03 Sc x O 3 -0.33BaTiO 3 and 0.67(Bi 1-x La y Fe 0.97 Ga 0.03 O 3 )-0.33(BaTiO 3 ) abbreviated as BFSBT-x and BLFBT-y respectively where x, y ≤ 0.07 were synthesized via site engineering, using solid-state route employing air quenching sintering technique. Site engineering is used to introduce the functionality by substituting A/B sites in respective solid solutions of these perovskites (general formula ABO 3 ). To better understand its effect, crystal structural, dielectric, optical, and ferroelectric properties were characterized and compared for different compositions. The X-ray diffraction pattern suggests the formation of pure perovskite structure with pseudocubic phase as the major phase present in both BFSBT-x and BLFBT-y series. The direct band gap energy of 1.97 eV and 2.14 eV lying in visible range was obtained for x=0.03 and y=0.03 composition, respectively. The temperature-dependent dielectric studies reveal frequency-dependent dielectric anomalies in permittivity corresponding to diffuse phase transitions stipulating relaxor-like behavior, which was further confirmed by modified Curie-Weiss law fitting. The enhanced temperature stability, good dielectric properties, and lower band gap suggest that site engineering is an efficient way to enhance the functional properties of BiFeO 3 -BaTiO 3 based samples for high-temperature applications.
Recently, the discovery of ferroelectricity in scandium-doped aluminum nitride (Al 1-x Sc x N) makes it a promising candidate to be used for next-generation ferroelectric memory applications. However, the large operating voltage hinders its practical use owing to its relatively large coercive field (E c ), which can be potentially reduced by strain engineering. Nevertheless, the relationship between stress and leakage current has not been investigated yet. In this work, we study the correlation between in-plane stress of AlScN film and leakage current of the ferroelectric Al 0.7 Sc 0.3 N-based capacitors. We observe that the leakage current relies closely on the film stress, in which less compressive stress will lead to smaller leakage current, providing the guidance for optimizing the film quality.
Piezoelectric micromachined ultrasonic transducers (PMUTs) are fabricated with Micro-Electro-Mechanical Systems (MEMS) processes. They have advantages such as high uniformity and density, high flexibility in array configuration, and compatibility with integrated circuits. However, the transmitting/receiving sensitivity and the bandwidth of PMUTs are usually lower than those of capacitive micromachined ultrasonic transducers (CMUTs) and conventional thickness mode transducers, which are vital for acoustical imaging resolution. This work presents a novel structure of piezoelectric micromachined ultrasonic transducer (PMUT) with dual piezoelectric driving at the device’s top surface, achieving better round-trip sensitivity while keeping cell size small compared with traditional PMUTs. Due to the high transmitting performance of the PZT film and the high receiving performance of the AlN film, the designed PMUT achieves ideal round-trip sensitivity-relative bandwidth product (Rt-SBW), which is 9.68dB higher than that of the optimized PZT-PMUT and 26.36dB higher than that of the optimized AlN-PMUT, greatly improving the pulse-echo imaging quality.
Piezoelectric materials are widely used in the field of structural health monitoring due to their ability to convert mechanical energy into electrical energy. This is achieved by generating an electrical potential difference through polarization under mechanical stress, which enables them to produce an electricity or voltage output. The aim of this study is to develop new piezoelectric polymer composites based on epoxy/ polyvinylidene fluoride (PVDF)/BaTiO 3 (BT) or silver additives. The composite was prepared by adding 20 wt.% PVDF and/or 5, 20 wt.% BT microparticles and 5 wt.% silver nanoparticles. The effects of different compositions were investigated in terms of their fracture toughness, tensile properties, piezoelectric response, thermal behaviour, and morphologies. The critical fracture energy of neat epoxy was obtained as G IC =810 J/m 2 . The addition of PVDF, BT and silver nanoparticles increased the critical fracture energy of the epoxy, with the maximum fracture energy value obtained as 1405 J/m 2 for the PVDF-BT containing epoxy composite. The addition of PVDF decreased the tensile modulus but increased the tensile strength, while silver nanoparticles decreased the tensile strength value from 59.5 MPa to 49.6 MPa due to agglomeration. The highest overall mechanical, thermal and piezoelectric response was observed in the epoxy-based polymer composite containing 20 wt.% PVDF and 5wt.% BT, which exhibited a maximum voltage output of ~0.2 V.
The performance of SOund NAvigation and Ranging (SONAR) is highly dependent on the properties of piezo-ceramic transducers. This paper presents a unique lamellar porous architecture for acoustic transducers, investigated by both experimental and simulation methods. Based on an ice-templating fabrication process, the resulting porous materials (BCZT) exhibit high hydrostatic figures of merits and improved acoustic impedance matching with the water. Simulation studies are conducted using a capacitor connectivity model to predict material properties, which are compared with experimental data obtained via a Berlincourt meter that operates under hydrostatic conditions (dh-meter). High hydrostatic figures of merit are achieved using porous ferroelectric ceramic structures, projecting the performances for future SONAR applications.
Reliability and yield are major concerns for memory devices. The random variability sources have a significant impact on the reliability of the memory window (MW) in ferroelectric FETs. In this work, through a comprehensive study, we analysed the impact of the non-uniform dielectric phase and metal grains on the coercive field of Metal-Ferro-Metal capacitor and on the performance of FeFETs. We found 1) Metal grains randomization (MGR) causes polarization non-uniformity throughout the volume of the ferroelectric layer; 2) Smaller metal thickness (T metal ) causes larger polarization non-uniformity due to work function discreteness. It leads to higher device variability and results in memory window closure; 3) Larger the metal grain size (MGS) higher will be the device variation; 4) The combination of higher the DE phase along with the higher DE grain size and larger the MGS with T metal causes worst-case reliability issues.
This paper reports on the design, fabrication, and experimental validation of an aluminum scandium nitride (AlScN) based Ferroelectric Micro-Electro-Mechanical Systems (FeMEMS) Multiplier—a core component for multiply-accumulate (MAC) operations in next-generation in-memory computing applications. The FeMEMS multiplier leverages ferroelectric polarization switching in AlScN to change the piezoelectric coefficient (d 31 ), facilitating non-volatile, analog memory storage for weights in a neural network. The piezoelectric parameters of the films are then used to change a capacitive gap for readout. The ferroelectric thin films could be partially polarized and reached a peak remnant polarization of 216µC/cm 2 at a voltage of 100V V P (5MV/cm). Experimental results on optically measured displacements confirmed the AlScN unimorph multiplier’s operation. The maximum resonance mode displacement was linearly dependent on the polarization and input voltages. This work provides foundational insights into utilizing AlScN in in-memory computing, opening new avenues for high-speed, low-power, and high-accuracy computing applications.
A structural strain of piezoelectric material and the strain suppression through modifying the fabrication process were discussed from the viewpoint of high piezoelectric conversion efficiency of the statically buckled diaphragm structures. The conversion efficiency of a vibrating piezoelectric diaphragms is enhanced by a static buckling of the diaphragm, whereas a too large buckling decreased the efficiency due to a too large tensile strain of the piezoelectric PZT film when the diaphragm buckles in the fabrication process. In this study, modified fabrication processes were proposed so that the PZT film is deposited on the already buckled diaphragm structure, and preparation condition of the bottom electrode of platinum/titanium films were also modified to reduce the residual tensile stress of the films to enhance the buckling deflection. The conversion efficiency improvement by using these process modifications was estimated through numerical evaluation of the buckling deflection. The analytical results showed that the process modifications suppressed the additional tensile strain and much enhanced the buckling deflection, and the efficiency improvement by 4.6 times was expected.
Radio frequency (RF) magnetic devices are key components in RF front ends. However, they are difficult to miniaturize and remain the bulkiest components in RF systems. Acoustically driven ferromagnetic resonance (ADFMR) offers a route towards the miniaturization of RF magnetic devices. The ADFMR literature thus far has focused predominantly on the dynamics of the coupling process, with relatively little work done on the device optimization. In this work, we present an optimized 2 GHz ADFMR device utilizing relaxed SPUDT transducers in lithium tantalate. We report an insertion loss of -13.7 dB and an ADFMR attenuation constant of -71.7 dB/mm, making this device one of the best performing ADFMR devices to date.
This study focuses on the exploration of electromechanical properties of polyvinylidene fluoride (PVDF) using a new characterization tool for piezoelectric polymers. The theoretical background is briefly described, then the experimental setup is shown, results are presented and discussed. The study puts emphasis on the temperature and humidity dependency of d 31 of PVDF. Finally, a short conclusion is given.
Domain reversal induction by a vertical electric field is studied at various temperatures in POI substrates. Extensive electrical and physical characterization is used to establish a correlation between stress conditions, switched domains area ratio and resonator performance. A tentative explanation is given for the unusual domain switching mechanism.
With the adoption of the internet of things (IoT) and wearable electronics, low size weight and power (SWaP) flexible hybrid electronics (FHE) are being installed in configurations that lead to large stresses on the various components. These stress levels may lead to large stresses and deformation of the flexible PCB boards traces, dielectric layers, and IC connections, which may affect its performance. In order to monitor installation stresses, a piezoelectric sensor was developed. 120 μm PVDF thick films were used because of its ease of integration with flexible electronics and its large, g 33 , which was measured to be 0.287 Vm/N. These piezoelectric sensors were incorporated with a TI MSP430 Micro-Controller Unit (MCU) to record and respond to stress levels. The analog input on the MCU has an input impedance of 35 kΩ. A Thevenin equivalent model of the piezoelectric source and pull-up resistors with different impedances was modeled in spice. From these results, an impedance-matching circuit was built to maximize the digitized stress signal. Above a certain output voltage, the MCU was programmed to turn on a LED to alert the end user the stress threshold was reached. At radius of curvature of 10 mm, the flexible PCB failed, and this became the threshold to turn on the LED. This study demonstrates a novel use case of piezoelectric sensors for FHE and details the importance of impedance matching and circuit design for transitioning piezoelectric films with external circuits and hardware.
Lead-based piezocrystals have been thoroughly investigated by various research teams for power ultrasonic transducers. The key objective of this work is to evaluate whether Gen. III single crystal could provide similar performance to the Navy type I (similar properties to PZT-4) and help in miniaturising the overall length of power ultrasonic instruments. This study started by incorporating four different material rings, Pz24, Pz26, and PIC181, as modified PZT-4, and Mn: PIN-PMN-PT (Gen. III single crystal) in cylindrical bolted Langevin transducers (BLTs) and comparing their key performance with respect to mechanical quality factor, electromechanical coupling coefficient, non-linearity, vibration response and nodal plane location. For the same operating frequency for all BLTs, the Gen. III single crystal transducer was found to be the shortest in length by 8~11 mm (7.6 ~ 10.4%). When testing the vibrational amplitude, the Gen. III single crystal has the highest tip normal-to-surface amplitude with lower current compared to other transducers. Gen. III was found to not follow the same non-linear behaviours as the piezoceramics transducer. Thus, the Gen. III transducer undergoes a change of material properties and depolarisation when excited with high voltage.
Diamond FET and MEMS devices are developed using a high-quality single crystal epilayer grown by a microwave plasma chemical deposition technique. A hydrogen-terminated diamond surface, a metal/diamond contact interface, and a smart cut technique are a key role to obtain excellent device performance.
Diluted magnetic semiconductors (DMS), in which transition metal (TM) ions primarily substitute cations of the host material form a class of spintronic materials. They exhibit ferromagnetism(FM) and half metallicity. Knowledge of magnetic interactions is crucial for obtaining room temperature ferromagnetism in a DMS. II-VI and III-V semiconductors are proving to be advantageous owing to their wide band gap, electric and piezoelectric properties and find a wide range of applications in optoelectronics, power electronics and spintronics [1]–[5].
Piezoelectric micromachined ultrasonic transducers (PMUTs) are fabricated with Micro-Electro-Mechanical Systems (MEMS) processes. They have advantages such as high uniformity and density, high flexibility in array configuration, and compatibility with integrated circuits. However, PMUTs generally have bottleneck issues with round-trip sensitivity, which restrict the improvement of acoustical imaging resolution. In this work, a round-trip modeling and optimization method is proposed to better analyze the round-trip sensitivity and solve the round-trip bottleneck problem of the PMUTs. Besides, the COMSOL livelinked with MATLAB to greatly simplify the calculation complexity is used to eliminate the influence of geometric parameters on center frequency variations and sweep several radii and thickness parameters.
This paper summarizes the sputter deposition of epitaxial PZT family including PZT, PMnN-PZT, and Sm-doped PMN-PT and the development of pMUTs (piezoelectric micromachined transducers) using epitaxial PZT family films. The deposition method, the choice of buffer layers, and the results of characterization are briefly reported. Using epitaxial PZT, epitaxial PMnN-PZT, fibered epitaxial PZT and heterogeneously stacked piezoelectric films, various designs of pMUTs were fabricated and tested. The problem and challenges to address toward practical applications are also presented.
A lot of interest has recently been paid in the field of photovoltaics, to the ferroelectric perovskite oxides, because of their special qualities, which include the availability of these materials in large quantities, the potential for charge carrier separation caused by polarization, high open circuit voltages, and chemical stability. However, ferroelectric perovskite oxides have a broad band gap due to which only slightly absorb solar light. In this study, we demonstrate how the optical band gap of BaTiO 3 can be lowered by doping this perovskite oxide with Ni and Nb at the Ti-sites. The structural, optical, and ferroelectric properties of BaTi 1−x (Ni 1/3 Nb 2/3 )xO 3 ceramics are investigated. X-ray diffraction studies confirm the formation of phase-pure perovskites of BaTi 1−x (Ni 1/3 Nb 2/3 ) x O 3 . A coexistence of the tetragonal and orthorhombic structures was observed for the developed compositions and their fraction varies with changing Ni and Nb doping concentrations. All the studied compositions show ferroelectricity at room temperature. The band gap of BaTiO 3 reduces from 3.2 eV to 2.06 eV for x= 0.07 composition for BaTi 1−x (Ni 1/3 Nb 2/3 ) x O 3 ceramics. There is an additional secondary band gap obtained for this composition. The presence of secondary band gap provides more light absorption sites and thus can be more useful for photo-absorbing layer in solar cells. Thus the new low band gap composition of BaTi 0.93 (Ni 1/3 Nb 2/3 ) 0.07 O 3 can be highly useful as ferro-photovoltaic material.
