Search Results (388)

Glow-discharge plasma (GDP) poling is revisited as an electrode-free method for activating piezoelectricity in poly(vinylidene fluoride) (PVDF) films. Although this method was proposed several decades ago, its effect on the properties of PVDF films has remained poorly understood. In this work, we demonstrate that GDP enables efficient poling of oriented PVDF films without pre-deposited electrodes and investigate the relationship between plasma treatment time, structural evolution, and piezoelectric response. Commercially available 25 μm-thick oriented PVDF films (PolyK) were treated in a DC glow discharge for 15 s to 15 min and characterized using FTIR, DSC, piezoresponse force microscopy, UV–Vis–NIR spectrophotometry, quasi-static d₃₃ measurements and water contact-angle measurements. GDP poling produced a side-averaged piezoelectric coefficient d₃₃ of up to ~25 pC/N within 1–5 min, with local maxima at approximately 1, 2.5, and 5 min. This behavior was accompanied by pronounced changes in the domain structure, including an increase in the ferroelectric domain size from 86 to 552 nm, while the crystallinity and electroactive phase fraction changed only moderately. Plasma treatment also increased the wettability of the plasma-facing surface, reducing the water contact angle from about 85° to 42° within 3 min. At longer treatment times (>5 min), however, the piezoelectric response decreased and the optical transparency deteriorated because of increased haze and turbidity, most likely associated with plasma-induced chemical modification of the surface layers. These results indicate that GDP poling has an effective processing window of 1–5 min. The proposed approach provides a vacuum-compatible and electrode-free route for preparing PVDF films with increased surface wettability for flexible piezoelectric sensors, wearable electronics, and integrated polymer-based devices, because it is compatible with electrode deposition on an already activated polymer surface within a single vacuum cycle. Full article

HfO₂ based thin-film ferroelectrics are metastable at room temperature and transited to the dielectric monoclinic phase upon heating. The thermal stability of such ferroelectrics increases when thin-film oxides are buried (BOX) in silicon–ferroelectric–silicon (SFS) structures formed by SmartCut^®, where thin ferroelectric layers are stabilized by oxygen vacancies and tensile stresses in the BOX, which is similar to silicon-on-insulator (SOI) structures. The main characteristics of the ferroelectrics in MFS and SFS structures are residual polarization P_r and coercive field E_c, which are determined by the fraction of the metastable ferroelectric phases that are also stabilized due to the inserted Al impurity in HfO₂:Al₂O₃ 10:1 (HAO) and (HfO₂:ZrO₂):Al₂O₃ (1:1)₅:1 (HZAO) nanolaminates. SFS structures and SFS CMOS ICs were tested after all thermal treatments at temperatures 900–1000 °C with t_BOX = 10–20 nm (or equivalent oxide thickness EOT = 1–2 nm) in an industrial process as gate insulators for CMOS and dual-gate DG SFS transistors. Their characteristics simulated in TCAD Sentaurus and analytic models in LTspice are investigated for an analog content addressable memory (ACAM). Full article

Dielectric capacitors are employed in defense and automotive applications owing to their ultrahigh charge–discharge rates. To mitigate the high leakage current density of Na_0.5Bi_0.5TiO₃ (NBT), SrTiO₃ (STO), which exhibits excellent insulation performance, is incorporated into the NBT lattice to enhance both the breakdown field strength and the relaxor characteristics. Furthermore, the ionic radius of Sr²⁺ (0.1180 nm) is slightly larger than the average ionic radius of (NaBi)²⁺ (0.1025 nm). As a result, the introduction of STO induces lattice distortion, disrupts long-range ordering, and promotes the formation of short-range ordered domains, thereby strengthening the relaxor behavior (the relaxation degree γ increased from 1.63 to 1.84). Consequently, the 0.95(Na_0.5Bi_0.5)(Fe_0.02Ti_0.99)O₃-0.05SrTiO₃ thin film achieves a recoverable energy storage density (W_rec) of 43.88 J/cm³ and an efficiency (η) of 73.95%. In addition, the thin film exhibits excellent temperature stability over a range of 10 to 170 °C, good frequency stability from 0.1 to 2.0 kHz, and robust fatigue endurance up to 1 × 10⁸ switching cycles. This work provides reliable technical and theoretical guidance for the application of NBT-based materials in energy storage. Full article

We report a CMOS-compatible ferroelectric memristor based on a TiN/AlScN/n⁺ Si metal ferroelectric semiconductor (MFS) structure, fabricated entirely via low-temperature sputtering processes. The ultrathin AlScN film exhibits robust ferroelectricity with a high remanent polarization (2P_r ≈ 80.91 μC/cm²) and excellent endurance over 10⁵ cycles, while maintaining uniform switching across cells. Notably, the use of a heavily doped silicon bottom electrode enables full compatibility with conventional back-end-of-line (BEOL) CMOS processes and facilitates integration with silicon-based circuits. Beyond stable memory performance, the device demonstrates volatile short-term memory (STM) behavior originating from depolarization field-induced polarization relaxation, which is essential for neuromorphic dynamics. Leveraging this STM feature, the device was implemented as a physical reservoir in a reservoir computing (RC) framework, achieving 97.64% classification accuracy on the MNIST dataset using temporally coded inputs. These results highlight the potential of AlScN-based ferroelectric memristors as dynamic CMOS-compatible building blocks for in-memory and neuromorphic computing. Full article

Barium-doped Lead Zirconate Titanate Pb_0.9Ba_0.1(Zr_0.53Ti_0.47)O₃ films with a (001)-dominant orientation were deposited on bulk silicon (Si) substrates using pulsed laser deposition (PLD). Due to the large electromechanical coupling coefficient (K²) of the P(B)ZT layer and the larger shear modulus of the Si substrate compared to the P(B)ZT film, it is possible to obtain higher-order acoustic-resonant modes (Sezawa mode) with SAW wavelength (λ)–piezoelectric film thickness (h) ratios below h/λ < 0.2. Due to the ferroelectric properties of the P(B)ZT film, the resonator’s performance can be improved by increasing the electric polarization. Consequently, the measured quality (Q) factors can be improved from 50 to 200 and the K² values can be improved from 2 to 5% with the resonance frequency ranging from 275 to 500 MHz. Full article

Y-doped HfO₂ ferroelectric thin films were fabricated via the sol–gel chemical solution deposition method. The effects of Y doping concentration, film thickness, and annealing temperature on the structure, morphology, and electrical properties were systematically investigated. The results demonstrate that doping concentration, film thickness, and annealing temperature can significantly regulate the crystalline phase composition. Appropriate doping, moderate film thickness, and suitable annealing temperature effectively stabilize the ferroelectric orthorhombic phase and suppress the monoclinic phase. The optimized film is obtained under the conditions of 4 mol% Y doping, a film thickness of 59.2 nm, and rapid thermal annealing at 600 °C, which exhibits the best crystallinity, dense and flat surface, and moderate oxygen vacancy concentration. The optimized sample shows a remnant polarization of 86.9 μC/cm², a coercive field of 1.1 MV/cm, and a leakage current density as low as 9.77 × 10⁻⁶ A/cm², representing the best ferroelectric performance. This study provides a reliable process and experimental basis for the preparation of high-performance HfO₂-based ferroelectric thin films by the sol–gel method. Full article

Crystallization temperature was tuned to control the crystal structure and relaxor behavior of Na_0.5Bi_5.5Ti₄AlO₁₈ films. This established a structure–property regulation pathway, enabling controlled transitions from ferroelectric, non-ergodic relaxor to ergodic relaxor states. Precise crystallization temperature control reduced grain size, thereby increasing both bulk resistivity and breakdown strength via suppressed conduction pathways. The Na_0.5Bi_5.5Ti₄AlO₁₈ film achieves outstanding energy storage performance when crystallized at 500 °C, delivering a recoverable energy density of 49.6 J/cm³ and an energy efficiency of 73.5% at an applied electric field of 2820 kV/cm. It also exhibits excellent thermal and frequency stability. Thus, crystallization temperature control is a direct, effective lever for optimizing dielectric energy storage films. Full article

Electrical measurements of emerging materials such as thin films, two-dimensional materials, and fragile porous systems are often hindered by damage and contamination caused by conventional contact methods, including metal electrode deposition. In this study, we demonstrate the novelty and advantages of a mechanically compliant “soft probe” over conventional methods and conductive AFM. The non-destructive soft probe achieves stable electrical contact in the repulsive-force regime using a hairpin-shaped spring structure, allowing consistent measurements without active force control nor electrode fabrication. Case studies demonstrate that the soft probe prevents metal penetration and preserves intrinsic properties, as demonstrated in NiO resistive switching devices, and improves interface quality compared to deposited electrodes in ferroelectric measurements. It also enables electrical characterization of fragile materials such as metal–organic frameworks without inducing structural degradation. Furthermore, its mechanical compliance ensures stable operation under vibration and thermal stress, enabling measurements in vacuum and low-temperature environments. These results indicate that the soft probe provides a simple, versatile, and contamination-free platform for reliable electrical measurements, and represents a promising approach for the characterization of a wide range of emerging material systems. Full article

Artificial muscles are an emerging class of actuators designed to mimic the compliant, efficient, and versatile behavior of biological muscles for fields including the following: soft robotics, prosthetics, wearable enhancements, haptic interfaces, and biomedical devices. These systems encompass various actuation mechanisms, including pneumatic, hydraulic, thermal, ionic, electrochemical, and electrostatic. Each with distinct tradeoffs in voltage, strain, output force, bandwidth, efficiency, and manufacturability. Among them, electrostatic actuators have attracted increased attention due to their fast response times, high energy densities, strong compatibility with soft materials, and scalability from microscale devices to large-area and stacked actuators. However, challenges such as dielectric breakdown, material fatigue, and fabrication complexity continue to limit widespread deployment. This review presents a structured classification of various artificial muscle technologies and an in-depth examination of electrostatic actuators including dielectric elastomers, electrostrictive and ferroelectric polymers, liquid crystal elastomers, electrostatic film motors, stacked architectures, and microscale/milliscale devices. In this review the operating principles, materials, architectures, performance characteristics, and failure modes of electrostatic actuators will be discussed. Additionally, a comparison will highlight tradeoffs across actuator families based on metrics such as voltage, force, strain, bandwidth, and manufacturability. Lastly, we outline future research directions in materials, physics-informed modeling, system integration, and scalable fabrication necessary to advance electrostatic artificial muscles toward practical, real-world deployment. Full article

Polymer–ceramic piezoelectric composites are widely investigated to combine the high piezoelectric performance of ferroelectric ceramics with the flexibility and processability of electroactive polymers. However, achieving enhanced dielectric properties while preserving the intrinsic piezoelectric response of the polymer matrix remains challenging, particularly due to dielectric mismatch between the constituent phases and interfacial effects. In this work, barium titanate (BaTiO₃) loaded poly(vinylidene fluoride-trifluoroethylene) (PVDF-TrFE) nanocomposites were fabricated by solvent casting using polyvinylpyrrolidone (PVP) and polysorbate 80 (PS80) as dispersing agents, aiming to obtain polarizable materials capable of retaining high piezoelectric strain coefficient (d₃₃) values and potentially exploiting the opposite polarity of matrix and filler through tailored poling strategies. Morphological, crystallographic, structural, thermal, thermomechanical, dielectric, and piezoelectric characterizations were performed by SEM/EDXS, XRD, FTIR, DSC, TGA, DMTA, dielectric spectroscopy, and d₃₃ measurements. Both dispersants improved filler dispersion and film densification, increasing the crystalline fraction of the matrix, without altering the relative fraction of β-phase (up to 93%). PVP enabled moderate and stable permittivity enhancement with weak frequency dependence, whereas PS80 introduced an electrically active interfacial contribution that amplified low-frequency permittivity at high filler loadings but made the permittivity more frequency-dependent. The piezoelectric response (between −20 pC/N and −25 pC/N) remained predominantly governed by the polymer phase, suggesting limited polarization played by BaTiO₃. These results underlined the critical role of interfacial electrical properties in designing stable high-performance flexible PVDF-TrFE/BaTiO₃ composites. Full article

Misfit strain between the substrate and the superlattice plays a critical role in determining the domain configurations and ferroelectric properties of superlattice heterostructures. This implies that a proper substrate material can be selected to design and tailor the domain structure and the properties of the superlattice. However, the influence of the substrate-induced strain on domain structures and polarization switching processes under different substrates is difficult to observe experimentally. In this study, we employ the phase-field method to explore the effects of different substrates on the domain patterns and switching properties of superlattice heterostructures. A phase diagram mapping substrate lattice parameters against the electric field was constructed for ferroelectric (SrTiO₃)₈/(BaTiO₃)₈ superlattice thin films. Néel-type skyrmion structures were observed under an applied electric field and could be stabilized upon field removal. Two distinct switching modes were also identified, depending on the substrate. Additionally, we observed that misfit strain-induced hysteresis linearization enhances both recoverable energy density and energy storage efficiency, suggesting that superlattice heterostructures hold promise for energy storage applications. Our findings provide new insights into the switching mechanisms of superlattice structures and pave the way for designing next-generation functional nanoelectronic devices. Full article

Lead zirconate titanate (PZT) is a widely used material for applications in microsensors, actuators, and transducers. Due to its high piezoelectric coefficient, large dielectric constant, and strong polarization capability near the morphotropic phase boundary (Zr/Ti ≈ 52/48), it is considered one of the most attractive materials for micro-electromechanical systems (MEMS). These advantageous material properties strongly depend on the PZT layer’s microstructure and crystallinity, which are primarily determined by the choice of seed layer, deposition conditions, and the post-deposition annealing treatment that promotes the formation of the PZT’s perovskite phase. In this contribution, sputter-deposited PZT thin films were crystallized by conventional furnace annealing (CFA) to evaluate the effect of heating/cooling rates (1 °C·min⁻¹–7 °C·min⁻¹) within a temperature range of 450 °C to 700 °C on structural, electrical, and ferroelectric properties, with consideration of the seed layer preparation. We characterized the materials’ properties by X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), and measurements of the ferroelectric hysteresis, capacitance, and leakage current. All samples annealed at temperatures of at least 500 °C fully crystallized into the perovskite phase, independently of the heating/cooling rate. The best ferroelectric performance was achieved at 550 °C with a 1 °C·min⁻¹ heating/cooling rate, yielding a saturation polarization of 82.8 µC·cm⁻² and a remnant polarization of 36.9 µC·cm⁻² under a maximum applied field of 300 kV·cm⁻¹. Full article

Piezo-enhanced photocatalysis is progressively considered an eco-friendly technology for contaminant removal, harvesting not only solar energy but also mechanical vibrations found in nature. Multiferroic materials present a coupled effect of various properties and can potentially increase the applicability of this process. In this study, Cr- doped bismuth ferrite thin film was deposited on SrTiO₃ substrate by HiPIMS, and its photo-, piezo-, and piezo-photocatalytic efficiencies in Rhodamine B (RhB) degradation were analyzed. The highest removal percentage was found under the simultaneous exposure of visible light and mechanical vibrations, reaching 86.2% after 180 min. The calculated efficiencies for photo- and piezocatalysis were 12.2% and 83.7%, respectively. The rate constant (k) for piezo-photocatalysis was 16.1 times higher than that found during photocatalytic experiments. To assess the contribution of each reactive species to the decomposition process, different reagents were added to the Rhodamine B contaminated solution. The results revealed that when p-benzoquinone was used, the degradation efficiency declined significantly from 86.2% to 37.6%, suggesting that superoxide radicals (O₂^•−) play a key role in decomposing RhB molecules. The structural, chemical, optical, and ferroelectric changes caused by the catalytic processes were analyzed and linked to the proposed degradation mechanisms. The poor photocatalytic efficiency was linked to an improper band structure and an improper polarization orientation of the ferroelectric domains in the as-deposited film. The degradation mechanisms in piezo-photocatalysis were driven partly by the band bending caused by mechanical vibrations and partly by the reorientation of the induced polarization of the domains in the unstrained film. Full article

Hafnium oxide thin films have been extensively investigated for high-speed and low-power memory applications. Herein, we investigated the influence of oxygen vacancies and external stress on the ferroelectric characteristics of Al-doped HfO₂ (HfAlO). Compared with HfAlO with 14% oxygen vacancies, films with 21% oxygen vacancies could lower the polarization switching barrier and increase the fraction of the ferroelectric phase. Furthermore, significant external stress promotes ferroelectric phase formation, thereby enhancing ferroelectric characteristics. The remanent polarization achieved with W electrodes (2Pr = 38 µC/cm²) is about 18 times that of Au electrodes, owing to the lower thermal expansion coefficient of W electrodes. Density functional theory calculations and finite element analysis provide theoretical insights corroborating the experimental results, helping to pave the way for developing hafnium-based materials for next-generation in-memory computing applications. Full article

This study presents the results of chemical and morphological analyses of conductive layers, indium tin oxide (ITO) and silver, deposited on lead zirconium titanate (PZT) substrates, in the form of ITO/PZT, Ag/PZT, and PZT buffer samples. The buffer layer was also examined to assess any potential impacts on the interface and was obtained by etching silver-coated PZT discs in an acid sonification bath. The ITO/PZT discs were obtained by DC sputtering. Chemical and morphological analyses were conducted using Raman spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDS). XRD analysis revealed distinct diffraction peaks corresponding to the composition and crystalline structure of the various discs. This established the presence of the expected face-centered cubic (FCC) structure of silver, the perovskite phase of PZT, and the cubic bixbyite structure of the conductive ITO layer. SEM/EDS illustrated the particle distribution and elemental composition of the samples. Raman spectroscopy further corroborated the presence and identity of the surface layers of the samples. The results demonstrate that ITO/PZT structures have the expected compositions and identified impurities. SEM results give insight into possible effects on piezoelectric effects and integration into opto-electronic devices. Full article