Search

Polarization switching in van der Waals ferroelectric materials driven by an electric field remains robust even at the atomic layer limit, paving the way for advances in the miniaturization and integration of ferroelectric devices. Thus, understanding the modulation of ferroelectric properties in two-dimensional ferroelectric materials is essential for their efficient nanoscale applications. NbOI2, a recently confirmed van der Waals ferroelectric, offers an ideal platform for investigating in-plane spontaneous polarization at the nanoscale. We explored the influence of laser excitation on the ferroelectric polarization properties of NbOI2. In multilayer NbOI2 devices with in-plane configurations, no significant current signals were detected along the c-axis or b-axis (the ferroelectric polarization axis) in the absence of illumination. However, under laser excitation, the material exhibited clear hysteresis loop behavior along both the c-axis and b-axis, indicating that laser excitation effectively reduces the coercive voltage. Furthermore, at the same excitation wavelength, the current peak along the c-axis was larger, with more pronounced hysteresis loops. Our experimental findings demonstrate that laser excitation can lower the coercive field in multilayer NbOI2 and induce different electrical hysteresis behavior along different crystallographic orientations, providing valuable insights for the development of NbOI2-based optoelectronic devices. [ABSTRACT FROM AUTHOR]

Resistive strain sensors show great potential in motion detection, medicine and healthcare, and human–machine interaction owing to their ease of fabrication, simple structure, and adjustable electrical performance. However, developing high-performance flexible resistive strain sensors with high sensitivity, high linearity, and low hysteresis remains a challenge. In this work, we report an LMPs (liquid metal particles)/MXene/AgNWs strain sensor (LMA strain sensor) with high sensitivity (GF = 6.339), high linearity (R2 = 0.982 24), and low hysteresis (0.452%). In this process, AgNWs act as a bridge between the MXene nanosheets, and the change in contact area of the MXene nanosheets under stretching endows the sensor with high sensitivity. The aggregated LMPs function as a structural framework, capitalizing on their intrinsic fluidic characteristics to serve as an adhesive between silver nanowires (AgNWs) and MXene nanosheets. This approach effectively minimizes the interstitial spaces between AgNWs and MXene. The formation of Ti-O → Ga3+ coordination bonds between MXene nanosheets and LMPs has strengthened the interfacial interactions. Consequently, the sensor demonstrates superior linearity and low hysteresis. In addition, a sensitive layer with a buckled structure is obtained by stretch-release. The buckled structure inhibits inhomogeneous and irreversible connection losses of the sensitive material, further improving the sensor's mechanical durability. LMA strain sensors can accurately detect various human activities such as breathing detection, motion detection, and expression detection. This work will provide an avenue for developing high-performance strain sensors. [ABSTRACT FROM AUTHOR]

Nonlinear hysteresis modeling is essential for estimating, controlling, and characterizing the behavior of piezoelectric material-based devices. However, current deep-learning approaches face challenges in generalizing effectively to previously unseen voltage profiles. This Letter tackles the limitation of generalization by introducing the notion of neural operators for modeling the nonlinear constitutive laws governing inverse piezoelectric hysteresis, specifically focusing on the relationship between voltage inputs and displacement responses. The study utilizes two neural operators—Fourier neural operator and the deep operator network—to predict material responses to unseen voltage profiles that are not part of the training data. Numerical experiments, including butterfly-shaped hysteresis curves, show that in accuracy and generalization to unseen voltage profiles, neural operators outperform traditional recurrent neural network-based models, including conventional gated networks. The findings highlight the potential of neural operators for modeling hysteresis in piezoelectric materials, offering advantages over existing methods in varying voltage scenarios. [ABSTRACT FROM AUTHOR]

This Letter demonstrates a 1500-V enhancement-mode (E-mode) GaN-based high electron mobility transistors (HEMTs) based on the recessed-free structure. The E-mode GaN-based HEMTs fabricated based on the ultrathin barrier epitaxial structure have a small gate interface traps density (Dit) of ∼1012 cm−2 eV−1, which can be attributed to the avoidance of AlGaN etching in the gate region. Meanwhile, a small threshold voltage (Vth) hysteresis of 19 mV and a small subthreshold swing of 101 mV/dec are achieved in the fabricated devices with a Vth around 1.91 V. A small Vth shift of 0.05 V was achieved under positive gate voltage stress, indicating that the devices have good Vth stability. Meanwhile, a high yield of more than 90% has been achieved on 6-in. wafer, which provides a good scheme for the commercialization of E-mode HEMTs. [ABSTRACT FROM AUTHOR]

Shape memory alloys (SMAs) are the key components of actuators and sensors due to their shape memory effect and superelasticity. However, the thermal hysteresis associated with martensitic phase transformation limits their use in the long-duration precise control. We report a strategy that obtains SMAs with low hysteresis by constructing a composition-temperature pseudo phase diagram. This strategy is inspired by the physically parallel ferroelectric system where the hysteresis is minimized at the multiple phase coexistence point, due to the absence of energy barrier across different phases. Following this, an alloy in the phase diagram with a low hysteresis of about 5 K is synthesized. In contrast, those alloys compositionally different from the optimal one have large hysteresis. Microstructures characterization and diffraction analysis are employed to identify the multiple phase coexistence. The proposed strategy should be general and can shed light on the rational design of SMAs with low hysteresis. [ABSTRACT FROM AUTHOR]

Understanding ferroelectric characteristic is crucial, especially for elucidating the existence of ferroelectric and its relationship with hysteresis in hybrid organic–inorganic perovskites. Our focus is to evaluate the ferroelectric properties of MAPbI3 perovskite films by suppressing the rotation of the MA+ ions through the substitution of TMA+ cations. Our findings indicate that both MAPbI3 and MA0.85TMA0.15PbI3 exhibit non-ferroelectric properties at room temperature, which persist even after external polarization treatment. Further analysis reveals that the hysteresis in J–V characteristics is associated with ion migration phenomena. The external polarization treatment aids in releasing electrons from defect states, enabling them to revert to their original lattice sites. As a result, devices subjected to polarization treatment exhibit reduced hysteresis and enhanced photovoltaic performance. [ABSTRACT FROM AUTHOR]

Understanding ferroelectric characteristic is crucial, especially for elucidating the existence of ferroelectric and its relationship with hysteresis in hybrid organic–inorganic perovskites. Our focus is to evaluate the ferroelectric properties of MAPbI3 perovskite films by suppressing the rotation of the MA+ ions through the substitution of TMA+ cations. Our findings indicate that both MAPbI3 and MA0.85TMA0.15PbI3 exhibit non-ferroelectric properties at room temperature, which persist even after external polarization treatment. Further analysis reveals that the hysteresis in J–V characteristics is associated with ion migration phenomena. The external polarization treatment aids in releasing electrons from defect states, enabling them to revert to their original lattice sites. As a result, devices subjected to polarization treatment exhibit reduced hysteresis and enhanced photovoltaic performance. [ABSTRACT FROM AUTHOR]

Hysteresis related to first-order phase transformation in shape memory alloys, which is the macroscopic manifestation of energy dissipation, is detrimental to the precise control of actuation and causes structural and functional fatigue of components. It is of vital importance to explore high-performance shape memory alloys with low stress-hysteresis, large superelasticity, and wide temperature range operation in practical applications. Here, we have developed a Ni-Mn-Fe-In shape memory microwire, exhibiting an ultra-low stress-hysteresis and huge tensile superelasticity in a wide temperature range. The microwire shows a smooth surface and a single crystal structure (with ⟨001⟩A-oriented along the axial direction of microwire), and the microstructure of the microwire contains austenite matrix and sparsely distributed precipitates with an average size of 20–80 nm, all of which may be beneficial to obtain low hysteresis and large strains in the microwire. As a result, the microwire exhibits a minimum stress-hysteresis of as low as 8.5 MPa (with overall strain of 15.3%) and corresponding energy dissipation as low as 1.44 MJ/m3. The microwire always shows a low stress-hysteresis (less than 24 MPa) and low energy dissipation (less than 2.86 MJ/m3) above room temperature. The microwire shows a huge superelasticity with recoverable strains higher than 15% in the wide temperature range from 218 to 418 K. Together with the advantages of easy fabrication and no post-processing required, this microwire shows a tremendous potential for cyclic actuators and energy conversion devices under multi-field coupling. [ABSTRACT FROM AUTHOR]

Bi2−xTe2.4Se0.6 single crystals show gapless topological surface states, and doping (x) with vanadium allows to shift the chemical potential in the bulk bandgap. Accordingly, the resistivity, carrier density, and mobility are constant below 10 K, and the magnetoresistance shows weak antilocalization as expected for low-temperature transport properties dominated by gapless surface states of so-called three-dimensional topological insulators. However, the magnetoresistance also shows a hysteresis depending on the sweep rate and the magnetic field direction. Here, we provide evidence that such magnetoresistance hysteresis is enhanced if both three-dimensional bulk states and quasi-two-dimensional topological states contribute to the transport (x = 0 and 0.03), and it is mostly suppressed if the topological states govern transport (x = 0.015). It is proposed that the hysteresis in the magnetoresistance results from different spin-dependent scattering rates of the topological surface and bulk states. Generally, this observation is of relevance to the studies of topologically insulating materials in which both topological surface and bulk states exist. [ABSTRACT FROM AUTHOR]

Van der Waals (vdW) heterostructures based on inorganic layered materials have been demonstrated as potential candidates for a variety of electronic applications due to their flexibility in energy band engineering. However, the presence of unstable charge-trapping states in atomically thin two-dimensional (2D) materials may limit the performance of devices. Here, we aim to conduct a systematic investigation on hybrid heterostructured memory devices that consist of 2D layered organic and inorganic materials. The objective is to explore the potential of these devices in offering efficient charge-trapping states. Molybdenum disulfide (MoS2) is employed as a channel, while N, N′-Dimethyl-3,4,9,10-perylenedicarboximide (Me-PTCDI) serves as the charge-trapping layer to store charges from MoS2. The hysteresis window of these heterostructured devices can be effectively modified within a range of 13–70 V by manipulating both the thickness of the organic layer and the gate voltages. The largest hysteresis window is found in a combination of a few-layer Me-PTCDI (12.6 nm) and MoS2 (6 nm), showing a high on/off current ratio (>104) and a long retention time (104 s). Furthermore, the endurance test, which lasts for over 1000 cycles, demonstrates an exceptional level of stability and reliability. In addition, multilevel memory effects can be observed when gate pulses with different widths and amplitudes are applied. These 2D hybrid heterostructured devices have the capability to broaden the scope of material systems and present substantial potential for functional neuromorphic applications. [ABSTRACT FROM AUTHOR]

Electrocaloric effect and loss-induced self-heating are simultaneously investigated in single-crystalline relaxor 0.9Pb(Mg1/3Nb2/3)O3-0.1PbTiO3 by a direct, high-resolution method. Transients of the total temperature change for few-cycle electric field pulses allow to distinguish and individually determine the contributions from electrocaloric effect and self-heating with millikelvin temperature and submillisecond temporal resolution. Simultaneous dielectric measurements make the comparison of observed self-heating to hysteresis losses possible, where very good agreement is found. The loss factor as a figure of merit for electrocaloric materials is directly obtained from the combined determination of caloric temperature change and losses. [ABSTRACT FROM AUTHOR]

The influence of the interface contact condition on the resistive switching (RS) effects of metal/Nb:SrTiO3 heterojunctions was investigated. Two Au/Nb:SrTiO3 samples with or without in situ substrate cleaning treatment were fabricated. Through comparative analysis of I–V hysteresis and switching performance, it was observed that the RS effect in the heterojunction formed by the in situ cleaned Nb:SrTiO3 substrate was significantly weakened. In addition, the SEM image demonstrates intimate contact between metal and the in situ cleaned substrate. In contrast, the untreated Au/Nb:SrTiO3 interface exhibits poor contact. The poor contact, as confirmed by interface AFM and CAFM images, is responsible for the resistive switching observed. Our research provides an innovative approach to elucidating the mechanism of the resistive switching effect, which will pave the way for better application of the device. [ABSTRACT FROM AUTHOR]

In this Letter, we demonstrate the Schottky gated p-AlGaN/u-GaN/AlGaN p-channel field-effect transistors (p-FETs) with an extremely low interface state density of 2.5 × 1011 cm−2 eV−1. Benefiting from the high-quality Schottky interface with suppressed interface states, the excellent stability with negligible hysteresis is proved, even after ten sequential dual I–V sweeps at 150 °C. Meanwhile, the trap density, confirmed by the temperature-dependent conductance method, is still below 1012 cm−2 eV−1 at high temperature. Furthermore, the fabricated p-AlGaN/u-GaN/AlGaN p-FET with a gate to drain distance of 1.8 μm shows a breakdown voltage of −128 V and an effective on-resistance of 7.2 kΩ mm, which allows the further scale down in terms of the source–drain spacing to improve the conduction current for low voltage application. The ultra-stable I–V characteristics of the fabricated Schottky-gated p-AlGaN/u-GaN/AlGaN p-FETs show great potential for next-generation integrated circuit application at high temperatures. [ABSTRACT FROM AUTHOR]

The droplet impact process on a solid surface is divided into a spreading phase where the droplet reaches the maximum deformation followed by a retracting phase. However, in the case of surfaces with high contact angle hysteresis, these two phases are connected by a relaxation phase where the contact angle changes from the advancing to the receding contact angle almost without motion of the contact line. Although the relaxation time can represent a significant part of the total droplet contact time, this relaxation regime has been less explored, especially for superhydrophobic surfaces due to the challenge of designing such surfaces with controlled wetting properties. Here, we show that for superhydrophobic surfaces with large contact angle hysteresis, the relaxation time can be comparable to the spreading and retracting time. Our results indicate that both the contact angle hysteresis and the capillary forces play a major role in defining the relaxation time and that relaxation time scales with the inertial–capillary time when using the droplet relative deformation as the characteristic length scale for this relaxation regime. [ABSTRACT FROM AUTHOR]

The electric pulses induced responses of (V0.99Cr0.01)2O3 in hysteresis temperature range have been investigated. We observed that multiple nonvolatile resistance states can be tuned by electric pulses due to the first-order metal to insulator phase transition, and, moreover, a reset can be realized by joule heating conveniently. Our calculations showed that the potential difference near the metal-insulator boundaries but close to the insulating side is remarkably larger, driving the resistance jumps. The multi-resistance states or the nonvolatile resistance properties excited simply by electric pulses have profound significance for the explorations of solid-state devices. [ABSTRACT FROM AUTHOR]

The electric pulses induced responses of (V0.99Cr0.01)2O3 in hysteresis temperature range have been investigated. We observed that multiple nonvolatile resistance states can be tuned by electric pulses due to the first-order metal to insulator phase transition, and, moreover, a reset can be realized by joule heating conveniently. Our calculations showed that the potential difference near the metal-insulator boundaries but close to the insulating side is remarkably larger, driving the resistance jumps. The multi-resistance states or the nonvolatile resistance properties excited simply by electric pulses have profound significance for the explorations of solid-state devices. [ABSTRACT FROM AUTHOR]

This article presents an approach for modeling hysteresis in piezoelectric materials that leverages recent advancements in machine learning, particularly in sparse-regression techniques. While sparse regression has previously been used to model various scientific and engineering phenomena, its application to nonlinear hysteresis modeling in piezoelectric materials has yet to be explored. The study employs the least squares algorithm with a sequential threshold to model the dynamic system responsible for hysteresis, resulting in a concise model that accurately predicts hysteresis for both simulated and experimental piezoelectric material data. Several numerical experiments are performed, including learning butterfly shaped hysteresis and modeling real-world hysteresis data for a piezoelectric actuator. The presented approach is compared to traditional regression-based and neural network methods, demonstrating its efficiency and robustness. [ABSTRACT FROM AUTHOR]

Materials with grain contacts or partially closed cracks exhibit anomalous elastic behavior: hysteresis in quasi-static experiments and slow dynamics in fast dynamic ones. Albeit the behavior in the two cases (which correspond to very different strain ranges) appears different, it should stem from the same physics and, thus, could be modeled by a universal equation of state. We propose a modification of the standard acoustoelastic theory, introducing the concept of conditioning induced non-equilibrium strain, which allows us to predict the evolution of elastic wave velocity in both quasi-static and dynamic ranges, including the velocity anisotropy induced by external uniaxial loading. [ABSTRACT FROM AUTHOR]

In this Letter, the trap inhomogeneity within β-Ga2O3 is correlated with the conversion of Shockley–Read–Hall (SRH) recombination in NiO/β-Ga2O3 p+–n heterojunction diodes. For the virgin epi-wafer, both near-surface traps E2 (EC-0.82 eV) and E3 (EC-1.11 eV) and bulk E2* traps (EC-0.76 eV) are identified by a transient capacitance analysis, and the corresponding forward current–voltage characteristics of diodes are well fitted in the framework of field-dependent SRH recombination. The SRH recombination rates for E2, E3, and E2* traps are determined to be 1.3 × 107, 8.6 × 108, and 2.4 × 108 s−1, respectively. In this circumstance, carrier transport under forward bias is governed by trap-assisted tunneling through E3 traps with high recombination rates, and the hysteresis is pronounced. With the removal of the defective surface layer, E2 and E3 traps are almost completely eliminated, together with the reduced density of E2* traps to 5.6 × 1014 cm−3. The resultant diode performs an improved rectification ratio of >1011 at ±3 V and an enhanced reverse breakdown voltage of 1692 V. The elimination of near-surface traps leads to the conversion of carrier transport into the conventional SRH recombination, accompanied by the negligible forward hysteresis characteristics. The established fundamental correlation of carrier transport and traps within Ga2O3 is beneficial to develop a high-performance power rectifier toward practical applications. [ABSTRACT FROM AUTHOR]

The hysteresis effect is a vital issue in perovskite solar cells that warrants close scrutiny, of which ion migration and the resultant interfacial ion accumulation are widely considered to be the most important origination. However, owing to the lack of specific characterization tools to disentangle the complicated interaction between ions and charge carriers, it is yet unidentified which ionic species govern the hysteresis effect, bringing difficulties in further device optimization. Herein, adopting a home-built circuit-switched transient photoelectric technique, whereby ion migration dynamics can be studied without interference from photogenerated charge carriers, the role of different ions in the photoelectric conversion process is elucidated. As suggested by the experimental results, the hysteresis effect dominantly arises from the migration of organic cations instead of the halide anions and can be well interpreted in terms of the strongly coupled cation–electron pairs. On the basis of these findings, we showcase the effectiveness of suppressing the hysteresis factor by the inhibition of the methylamine cations' migration. The present work can provide targeted and sufficient guidance for the preparation of high-stability and high-efficiency perovskite solar cells. [ABSTRACT FROM AUTHOR]

In this work, the time-dependent behaviors of dual-channel amorphous InGaZnO (a-IGZO) thin-film transistors (TFTs) under negative bias illumination stress (NBIS) are systematically discussed. The dual-channel comprised two different IGZO layers fabricated by tuning the oxygen flow during deposition. The presence of heterojunctions enhanced field-effect mobility by 1.5× owing to the confinement of carriers in buried channels because of an energy barrier. However, after long periods of NBIS stress, the degradation of a-IGZO TFTs resulted in the entrapment of photo-generated electron–hole pairs at interface defects. The conduction path migrated to the surface channel. Results from extracting the hysteresis window and utilizing capacitance–voltage measurements have indicated a channel migration phenomenon due to the entrapment of electrons and holes at the surface and buried channel interfaces. [ABSTRACT FROM AUTHOR]

For Bi0.5Na0.5TiO3 (BNT)-based materials, regulating temperature and composition could both induce giant electro-strain under the critical condition. Nevertheless, only the temperature-dependent regulation method achieved low hysteresis and maintained a high strain under high ergodic condition simultaneously. Herein, we investigated the origin of this discrepancy by means of matrix with close strain level. These two regulation methods exhibited different regulation mechanisms, especially for the microscopic structure (i.e., the discrepant lattice structure and polar entities). The A-site and BO6 octahedral-dependent vibration modes exhibited obvious discrepancies under the highly ergodic condition, while the shift was relatively small around relaxor/ferroelectric crossover. Additionally, polar entities also exhibited discrepant morphology (e.g., composition-regulated one exhibited striped domains, and temperature-regulated one possessed fuzzy signals with partial nanosized domains under the critical condition) and kinetic behaviors (e.g., under highly ergodic condition, temperature-regulated polar entities rebounded slowly at the initial unloading stage). In a word, relatively small structural discrepancies leaded to similar strain performance under the critical condition, while the increasing ergodicity accompanied by increasing structural discrepancies, which finally induced different strain performance under the high ergodic condition. This insight for designing the BNT-based materials with giant electro-strain and low hysteresis was useful to accelerate the industrialization of eco-friendly actuators. [ABSTRACT FROM AUTHOR]

Lead-free Na0.5Bi0.5TiO3 (NBT) exhibiting large polarization and a high Curie temperature can be considered as a promising candidate for dielectric capacitors. The large polarization switching hysteresis and low breakdown field, however, restrict the performance optimization. Herein, epitaxial NBT-based high-entropy Na0.5Bi0.5Ti0.7Hf0.1Zr0.1Sn0.1O3 (NBTHZS) films are designed and prepared by solution-based processing. Compared with the NBT film, the polarization switching hysteresis is depressed and the breakdown field is significantly improved for the NBTHZS film due to the high-entropy effects. Therefore, the NBTHZS film achieves a ∼16 times enhancement of energy density (from 5.1 J/cm3 of the NBT film to 81 J/cm3 of the NBTHZS film) and a high efficiency of 74.1% as well as an excellent performance reliability. The results shed light on enhancing dielectric energy storage properties of NBT-based films by forming high-entropy structures. [ABSTRACT FROM AUTHOR]

Gradual switching in the memristor or memcapacitor devices is the key parameter for the next generation of bio-inspired neuromorphic computing. Here, we have fabricated the WOx/ZrOx dual-oxide layered device, which shows the coexistence of gradual resistive and capacitive switching arisen from the current and capacitance hysteresis curves, respectively. The expansion of hysteresis loop can be modulated by altering the oxygen content in the oxide materials. Interestingly, the presence of negative differential resistance (NDR) is dependent on the voltage sweep direction and range of applied bias, which can be reasoned by the local electric field, charge trapping/detrapping, and conduction band offset at the dual-oxide interface. This study provides the concept of the coexistence of current and capacitance hysteresis along with NDR, and it is highly potential for memristor and memcapacitor circuits to explore neuromorphic computing. [ABSTRACT FROM AUTHOR]

Piezoelectric microelectromechanical systems (piezoMEMS) enable dense arrays of actuators which are often driven to higher electrical fields than their bulk piezoelectric counterparts. In bulk ceramics, high field driving causes internal heating of the piezoelectric, largely due to field-induced domain wall motion. Self-heating is then tracked as a function of vibration velocity to determine the upper bound for the drive levels. However, the literature is limited concerning self-heating in thin film piezoMEMS. In this work, it is shown that self-heating in piezoMEMS transducer arrays occurs due to domain wall motion and Ohmic losses. This was demonstrated via a systematic study of drive waveform dependence of self-heating in piezoMEMS arrays. In particular, the magnitude of self-heating was quantified as a function of different waveform parameters (e.g., amplitude, DC offset, and frequency). Thermal modeling of the self-heating of piezoMEMS using the measured hysteresis loss from electrical characterization as the heat source was found to be in excellent agreement with the experimental data. The self-heating model allows improved thermal design of piezoMEMS and can, furthermore, be utilized for functional heating, especially for device level poling. [ABSTRACT FROM AUTHOR]

Layering elastocaloric materials can effectively maximize the average elastocaloric effect along the regenerator with a temperature gradient. An explicit correlation for mapping the performance of the layering elastocaloric regenerator from design parameters was developed by simplifying elastocaloric material property and energy conservation equations. Cooling capacity and coefficient of performance are found to be theoretically inversely linear with temperature span when the nonlinear dependence of elastocaloric heat on temperature is disregarded. The optimum utilization factor, the volume fraction of materials, the number of layers, and the transformation temperature spacing are obtained by confining the materials operating in the vicinity of their transformation temperatures. Performance degradation caused by hysteresis is found to be approximately linear with the hysteretic entropy change normalized by the isothermal entropy change. [ABSTRACT FROM AUTHOR]

In this Letter, we report a demonstration of p-channel tin monoxide (SnO) thin-film transistors (TFTs) with high field-effect mobility (μFE) exceeding 10 cm2/Vs and hysteresis-free like behavior. We demonstrate that maintaining metallic states before encapsulation is a key process to enhance μFE in p-type SnO thin-films. Sustaining this meta-stability involves the following two processes during fabrication: (1) postdeposition annealing (PDA) in two steps and (2) encapsulation in the middle of each PDA. This simple process not only suppresses creation of oxidized states such as adverse Sn4+ but also facilitates the lateral growth of crystals with improved crystallinity by interfacial energy stabilization. The resultant SnO TFT reveals a record-high μFE up to 15.8 cm2/Vs with a negligible hysteresis of 0.1 V. This study suggests a practical route to grant high μFE to p-channel SnO TFTs without any dopant or complex postdeposition treatment. [ABSTRACT FROM AUTHOR]

We propose a semi-suspended device structure and construct nanogapped, hysteresis-free field-effect transistors (FETs), based on the van der Waals stacking technique. The structure, which features a semi-suspended channel above a submicrometer-long wedge-like nanogap, is fulfilled by transferring ultraclean boron nitride-supported MoS2 channels directly onto dielectric-spaced vertical source/drain stacks. Electronic characterization and analyses reveal a high overall device quality, including ultraclean channel interfaces, negligible electrical scanning hysteresis, and Ohmic contacts in the structures. The unique hollow FET structure holds the potential for exploiting reliable electronics as well as nanofluid and pressure sensors. [ABSTRACT FROM AUTHOR]

Considerable interest to magnetism of MnAs both in bulk or in the form of epitaxial films is stimulated by its applications as a magnetocaloric material and in spintronic devices. Since the MnAs films deposited on GaAs reproduce well a magnetic transformation related to α–β magnetostructural transition that occurs in bulk MnAs, this first-order phase transition occurs through a phase coexistence over a wide temperature range. Here, we considered the same magnetostructural transition in a bulk hybrid structure based on micrometer-scaled MnAs inclusions embedded into the Cd3As2 matrix. In particular, the effect of high pressure and magnetic fields on the ferromagnetic transition temperature, TC, in a composite Cd3As2 + 30 mol. % MnAs has been studied. We found that at ambient pressure, the transition from α-MnAs to β-MnAs is accompanied by the absence of thermal hysteresis of magnetization, implying a phase coexistence regime. The hysteresis width does not markedly increase even at pressures about P = 0.35 GPa, and displacement of TC occurs with a rate of dTC/dP ∼ −91.42 K/GPa. In the temperature region of the α–β phase coexistence, a local peak at T = 283 K and P = 1 GPa is observed, which is associated with an antiferromagnetic order of MnAs inclusions. Direct measurements of isothermal magnetization vs pressure indicate both the stabilization of the ferromagnetic hexagonal α phase at P < Pmax and the development of an orthorhombic antiferromagnetic long-range order, which propagate up to 5 GPa. [ABSTRACT FROM AUTHOR]

Scaling behavior of dynamic hysteresis of (Na0.47Bi0.47Ba0.06)0.95A0.05TiO3 (A = Sr2+/Ca2+) (expressed as BNBT-Sr and BNBT-Ca, respectively) lead-free ceramics was comparatively studied. BNBT-Ca exhibits typical ferroelectric hysteresis (polarization vs electric field, P–E) loops, while BNBT-Sr shows pinched P–E loops. The two samples' electric field and frequency-dependent dynamic hysteresis behavior were systematically investigated. The dopants difference (Sr2+/Ca2+) produces different scaling behavior of dynamic hysteresis, which is related to the electric field-induced phase transition and domain size between BNBT-Sr and BNBT-Ca. [ABSTRACT FROM AUTHOR]

The domain reversal dynamics of rhombohedral and tetragonal PIN–PMN–PT ferroelectric single crystals has been investigated by analyzing the variation of hysteresis loops under various electric fields and frequencies. As the electric field amplitude E0 continuously increases, the hysteresis area ⟨A⟩ clearly reflects three stages of polarization reversal. The complete scaling relations of domain reversal dynamics were determined. For rhombohedral PIN–47PMN–29PT crystals, the dynamic hysteresis area follows the law of ⟨A⟩ ∝ f −0.38816E05.21244 in the first E0-stage and ⟨A⟩ ∝ f 0.03553E00.37126 in the third E0-stage. For tetragonal PIN–37PMN–39PT crystals, the dynamic hysteresis area follows the law of ⟨A⟩ ∝ f −0.09054E02.74854 in the first E0-stage and ⟨A⟩ ∝ f −0.15504E02.06936 in the third E0-stage. The negative α indicates that with the alternating velocity of the increasing periodic electric field, more and more domain reversals fail to follow with the alternating electric field. However, rhombohedral PIN–47PMN–29PT crystals possess a positive α in the third E0-stage, indicating that 71° and 109° domains can keep pace with varying E0 more easily. The positive β indicates that when the electric field frequency is fixed, more and more domains begin to reverse with the intensity of the increasing electric field. In addition, the function of ⟨A⟩ ∝ f αE0β cannot be applied to the second E0-stage, where the non-180° domain rotation starts occurring but 180° domain rotation has not finished yet. [ABSTRACT FROM AUTHOR]

Multiferroic magnetoelectric (ME) composites have been continually attracting researchers' attention because of the significant potential for building functional devices. Unlike conventional ME devices under quasi-static or low-power excitation, e.g., sensors, energy harvesters, and random memories, high-power ME devices like recently proposed ME antennas will perform complex dynamic behavior. The voltage-driven nonlinearity in 1–1-typed ME resonators was reported from the perspective of frequency-response curve in our last work. Here, we described both theoretically and experimentally a previously unobserved jumping and hysteresis effect in its magnetic bias characteristic. A direct link between the bias-response and the frequency-response characteristics was also experimentally provided to analyze the origin of the nonlinear behavior in the bias-response curve. In addition, the cubic spring constant k3 was theoretically calculated and compared to qualitatively explain the difference of our obtained threshold voltage that generated the first and second jumping resonances in the dual-peak bias-response curve. In contrast to our previous research, this work reveals the loading direction of the applied magnetic bias field, which plays a significant role when we consider the selection of an optimized bias field for high-power ME devices. Moreover, the sharp jumping in the bias-response curve is also a potential for opening dimensions for ME community. [ABSTRACT FROM AUTHOR]

The pyroelectricity of polar materials provides great potential for electricity generation from waste heat. The pyroelectric effect of the material can be magnificently enhanced at a first-order phase transformation due to the abrupt jump in spontaneous polarization within a narrow temperature range. Here, we show that the performance of energy conversion by phase transformation is inversely resonant with the hysteresis of thermally driven structural transformations in a (Ba1−xSrx) (Hf0.02Ce0.005Ti0.975)O3 system, corresponding to a singular lattice distortion mode satisfying the crystallographic compatibility condition. Among the finely tuned Sr compositions from 0.04 to 0.10, we discovered that Sr0.07 composition is a promising material candidate in this material system for pyroelectric energy conversion. Our work suggests a rational strategy of material development for pyroelectric energy conversion applications. [ABSTRACT FROM AUTHOR]

Graphene is utilized as a sensitive probe to explore the surface polarization phenomenon in SrTiO3 in this work. A ferroelectric-like hysteresis effect induced by the external electric field stimuli as well as a pyroelectric effect caused by the light stimuli is observed and discussed through the quasi-static/transient evolution of graphene current at a constant bias voltage. The existence of electric dipoles at the surface of SrTiO3 is confirmed. Dipoles are dependent on the external electric field, and there is an electric field induced remanent polarization after high electric field treatment. The pyroelectric phenomenon caused by the light illumination indicates that the electric dipoles naturally exist at the SrTiO3 surface even though there is no external electric field. [ABSTRACT FROM AUTHOR]

The presence of mobile ions in perovskites is well known to influence the device electrostatics leading to a wide variety of anomalous characteristics related to hysteresis, efficiency degradation, low frequency capacitance, large signal switching, etc. Accordingly, the ion mobility is understood to a have a critical influence on the associated time constants/delays. Quite contrary to this broadly accepted thought, here we suggest that the time delays associated with large signal switching could show a universal behavior dictated by electronic dipoles, rather than ionic dipoles. Due to the resultant sudden and dramatic collapse of a contact layer depletion region, large signal switching delays are independent of ion mobilities. Furthermore, our detailed numerical simulations, supported by experimental results, indicate that terminal currents show a near steady state behavior well ahead of the relaxation of ionic distributions. These results have interesting implications toward the understanding and optimization of perovskite based electronic devices, including solar cells, LEDs, resistive memories, and ferroelectric memories. [ABSTRACT FROM AUTHOR]

A long-standing puzzle in the understanding of magnetic materials is the "Permalloy problem," i.e., why the particular composition of Permalloy, Fe 21.5 Ni 78.5 , achieves a dramatic drop in hysteresis and concomitant increase in initial permeability, while its material constants show no obvious signal of this behavior. In fact, the anisotropy constant κ1 and the magnetostriction constants λ 100 , λ 111 all vanish at various nearby, but distinctly different, compositions than Fe 21.5 Ni 78.5 . These compositions are in fact outside the compositional region where the main drop in hysteresis occurs. We use our newly developed coercivity tool [A. Renuka Balakrishna and R. D. James, Acta Mater. 208, 116697 (2021)] to identify a delicate balance between local instabilities and magnetic material constants that lead to a dramatic decrease in coercivity at the Permalloy composition Fe 21.5 Ni 78.5 . Our results demonstrate that specific values of magnetostriction constants and anisotropy constants are necessary for the dramatic drop of hysteresis at 78.5% Ni. Our findings are in agreement with the Permalloy experiments and provide theoretical guidance for the development of other low hysteresis magnetic alloys. [ABSTRACT FROM AUTHOR]

Controlling the hysteresis effect in organic field-effect transistors (OFETs) is imperative to attain reliable devices that can be applied to complicated circuits for practical applications. In this Letter, we compare two naphthalene tetracarboxylic diimide (NDI) derivatives, namely, N,N′-bis(4-trifluoromethoxybenzyl) naphthalene-1,4,5,8-tetracarboxylic acid diimide (NDI-BOCF3) and N,N′-bis(hexyl) naphthalene-1,4,5,8-tetracarboxylic acid diimide (NDI-C6), which are comprised of different side chains and exhibit significant variations in the hysteresis of electronic transfer potential caused by the electronic traps. Among them, NDI-BOCF3 manifests negligible hysteresis in OFETs, while the counterparts based on NDI-C6 show notable hysteresis. This work presents insight into the hysteresis phenomenon of NDIs in OFETs, which depends on various critical factors, including interfacial trap density, molecular structure, thin film growth mode, and surface energy. Particularly, NDI-C6 demonstrates two orders of magnitude higher interfacial trap density than that of NDI-BOCF3. Moreover, NDI-BOCF3 thin film displays small surface energy and higher surface coverage on the substrate, but the results are diametrically opposite in the case of NDI-C6. Considering these observations, we propose that the introduction of OCF3 group in NDI not only endues a well-matched surface energy that promotes uniform distribution of the thin film on n-Octyltrichlorosilane-modified SiO2 substrate but also provides a water-spelling feature which leads to fewer H2O/O2 absorption in the resulting thin films. Our findings offer a fundamental guideline to rationally design n-type organic semiconductors for the development of efficient OFETs with negligible hysteresis. [ABSTRACT FROM AUTHOR]

The charge density wave (CDW) state in van der Waals systems shows interesting scaling phenomena as the number of layers can significantly affect the CDW transition temperature, TCDW. However, it is often difficult to use conventional methods to study the phase transition in these systems due to their small size and sensitivity to degradation. Degradation is an important parameter, which has been shown to greatly influence the superconductivity in layered systems. Since the CDW state competes with the onset of superconductivity, it is expected that TCDW will also be affected by the degradation. Here, we probe the CDW phase transition by the mechanical resonances of suspended 2H-TaS2 and 2H-TaSe2 membranes and study the effect of disorder on the CDW state. Pristine flakes show the transition near the reported values of 75 K and 122 K, respectively. We then study the effect of degradation on 2H-TaS2, which displays an enhancement of TCDW up to 129 K after degradation in ambient air. Finally, we study a sample with local degradation and observe that multiple phase transitions occur at 87 K, 103 K, and 118 K with a hysteresis in temperature in the same membrane. The observed spatial variations in the Raman spectra suggest that variations in crystal structure cause domains with different transition temperatures, which could result in the hysteresis. This work shows the potential of using nanomechanical resonance to characterize the CDW in suspended 2D materials and demonstrates that the degradation can have a large effect on transition temperatures. [ABSTRACT FROM AUTHOR]

In this paper, we demonstrate thermal bi-stability and hysteresis in hetero-phase molybdenum diselenide (h-MoSe2) consisting of 2H semiconducting MoSe2 and molybdenum oxide (MoOx) phases. h-MoSe2 exhibits pinched hysteresis in the current-voltage characteristics, with the lobe area increasing with decreasing temperature. High and low resistance states were encoded into the sample by thermal manipulation. Cooling the sample below room temperature (RT) drives it to a low resistance state ("1" state), whereas heating above RT switches it to a high resistance state ("0" state). The ratio between "1" and "0" resistance states was found to be greater than 2000 with arbitrary long retention time at room temperature. The results are discussed in terms of temperature-induced adsorption/desorption of water vapor and its interplay with the charge transfer in MoSe2. Our study indicates that h-MoSe2 can be a potential candidate for application in alternate memory devices such as thermal memory and memristors. [ABSTRACT FROM AUTHOR]

All-inorganic halide perovskites (AIHPs) have become one of the most promising materials for commercial perovskite photovoltaics owing to their enhanced efficiency and thermodynamic stability. Output instability, such as current hysteresis, is stressed in organic-inorganic hybrid perovskite photovoltaics but is neglected in AIHP solar cells. Here, the origin and suppression of current hysteresis in AIHP solar cells are addressed from a microscopic viewpoint. The incorporation of fullerene into AIHP films efficiently suppresses ion migration, which alleviates the macroscopic current hysteresis in solar cells. This result is confirmed by both Kelvin probe force microscopy and conductive atomic force microscopy measurements. Our results provide an advanced understanding of the microscopic properties of AIHPs but also clearly clarify how to suppress the macroscopic current hysteresis, which further inspires the optimization of solar cells up to the levels of organic–inorganic hybrid counterparts. [ABSTRACT FROM AUTHOR]

The electrocaloric effect (ECE) in dielectrics is characterized by the isothermal entropy change ΔS and adiabatic temperature change ΔT induced by changes of external electric fields. The Maxwell relation, which relates changes of polarization P with temperature T (pyroelectric coefficient) under a fixed electric field E to ΔS for finite intervals in E, provides a convenient way to deduce the ECE from polarization data P(T, E). Hence, this method, known as the indirect method, is widely used in ECE studies in ferroelectrics. Here, we first present the thermodynamic consideration for the Maxwell relation. We then use the indirect method and P(T, E) from bipolar and unipolar polarization curves to deduce the ECE in the normal ferroelectric phase of a P(VDF-TrFE) copolymer. The deduced ECE using the P(T, E) from bipolar polarization curves exhibits a giant negative ECE. In contrast, the directly measured ECE in the same polymer shows the weak and normal ECE. We discuss the constraints of the indirect method and its relation to the polarization–electric field curves measured in practical ferroelectric materials. [ABSTRACT FROM AUTHOR]

The use of Si-based materials can increase the energy density of lithium ion batteries by at least 20% compared to the conventional graphite-based anodes. However, Si-containing anodes are susceptible to rapid degradation due to severe volume changes on lithiation/delithiation during cycling. This Perspective presents the current understanding of the phase transformations occurring on lithiation/delithiation of Si-based materials and specifically relates these to hysteresis. Challenges and strategies in the pursuit of higher capacity and longer cycle life anodes are discussed. Thermodynamic considerations are shown to represent an important step in the design of electrode materials with improved electrochemical performance. [ABSTRACT FROM AUTHOR]

In this Letter, we report a high-performance NiO/β-Ga2O3 pn heterojunction diode with an optimized interface by annealing. The electrical characteristics of the pn diode without annealing (PND) and with annealing (APND) are studied systematically. The APND device has a lower specific on-resistance of 4.1 mΩ cm2, compared to that of the PND, 5.4 mΩ cm2. Moreover, for the APND, a high breakdown voltage of 1630 V with lower leakage current is achieved, which is 730 V higher than that of the PND. The enhanced electrical performance of the APND leads to a record high power figure of merit of 0.65 GW/cm2 in Ga2O3-based pn diodes, which is among the best reported results in Ga2O3 power devices. In addition, the interface trap density of the diode decreases from 1.04 × 1012 to 1.33 × 1011 eV−1 cm−2 after annealing, contributing to much lower hysteresis. Simultaneously, the ideality factor n for the APND is steady at elevated temperatures due to the stable interface. The results of C − V characteristics reveal the bulk defects inside the nickel oxide film grown by sputtering, which are calculated by high- and low-frequency capacitance methods. X-ray photoelectron spectroscopy of NiO illustrates the reasons for the changes in the concentration of holes and defects in the film before and after annealing. This work paves the way for further improving the performance of Ga2O3 diode via interface engineering. [ABSTRACT FROM AUTHOR]

The Gibbs energy can yield fundamental insight into the material properties of ferroelectrics such as energy barriers and phase transitions. Particularly for newly emerging classes of ferroelectric and antiferroelectric materials, such as fluorite-structured HfO2 and ZrO2, the Gibbs energy can bridge theoretical calculations with experimental observations. Experimentally observed dynamic double hysteresis loops in thin film ZrO2 and Si-doped HfO2 capacitors are used to obtain a solution to the Gibbs energy by calculating the internal electric field with depolarization. By accounting for dipole-field interaction energies and static energies in the solution of the Gibbs energy of double-hysteresis ZrO2 and Si-doped HfO2, a characteristic triple-well with two polar and one nonpolar energy minima emerges. Macroscopic metastable polar and nonpolar phases close in free energy are shown to be in agreement with first-order phase transitions underlying double hysteresis in ZrO2 and Si-doped HfO2. The application of an external field is demonstrated to lower the free energy minimum of the polar phase below the nonpolar phase, providing macroscopic support that a first-order phase transition driven by an electric field is responsible for antiferroelectric behavior in doped HfO2 and ZrO2. Energy barriers for the nonpolar → polar phase transition from 0.75 to 4.3 meV per formula unit are calculated for ZrO2 and Si-doped HfO2. The macroscopic Gibbs energy profiles obtained through experimental measurements and device modeling connect the fundamental phenomenology of ferroelectrics and antiferroelectrics to electronic devices. [ABSTRACT FROM AUTHOR]

A method to reduction hysteresis loss of soft magnetic composites (SMCs) is reported in this Letter. It is found that the power loss of SMCs reduces about 1/3 at the expanse of less than 10% decreases of permeability when a transverse magnetic field is applied in the SMC core. This power loss reduction comes from the decrease in hysteresis loss of composites, and this reduction is influenced by transverse magnetization state. This hysteresis loss reduction is attributed to domain wall displacements and spin rotations being completely locked in the direction of the transverse field, and this effect has great application potential in high-power electrical systems. [ABSTRACT FROM AUTHOR]

We investigate the origin of the variation in resistive switching hysteresis of VO2 thin films. Using pulsed electrical measurements in textured VO2 thin film devices, we show that the hysteresis observed in I–V curves results from Joule heating effects, particularly in the low-resistance state. The hysteresis is reduced by increasing the cooling time between pulses. Based on a mechanism of Joule heating-induced metal-insulator transition, numerical simulations are performed, which agree with the experimental variation in the hysteresis. Finally, a framework for engineering the I–V curves of VO2 devices is proposed. [ABSTRACT FROM AUTHOR]

The accurate determination of electrocaloric coefficients in nanometer-thin, polycrystalline doped HfO2 is challenging and has led to very different values reported in the literature. Here, we apply two different methods in order to compare and analyze reversible and irreversible or metastable contributions to the electrocaloric effect. The indirect method is based on temperature-dependent ferroelectric hysteresis characteristics. Furthermore, we apply a direct method, where electrocaloric temperature variations are observed using a specialized test structure. A comparison of both methods reveals that the indirect method dramatically overestimates the response due to thermal fatigue effects, which are caused by the migration of charged defects to the electrode interfaces. The partial transition to the antiferroelectric-like tetragonal phase is not immediately reversed to the polar Pca 2 1 phase upon cooling. An electrocaloric coefficient of − 107 μ C m − 2 K − 1 is determined for a 20 nm thick Si-doped HfO2 film with the direct method, which corresponds to a Δ T of 4.4 K. [ABSTRACT FROM AUTHOR]

We characterize InSb quantum dots induced by bottom finger gates within a nanowire that is grown via the vapor–liquid–solid process. The gates are separated from the nanowire by an exfoliated 35 nm thin hexagonal BN flake. We probe the Coulomb diamonds of the gate-induced quantum dot exhibiting a charging energy of ∼ 2.5 meV and orbital excitation energies up to 0.3 meV. The gate hysteresis for sweeps covering 5 Coulomb diamonds reveals an energy hysteresis of only 60 μeV between upward and downward sweeps. Charge noise is studied via long-term measurements at the slope of a Coulomb peak revealing a potential fluctuation of ∼1 μeV/ Hz at 1 Hz. This makes h-BN a dielectric with the currently lowest gate hysteresis and lowest low-frequency potential fluctuations reported for low-gap III–V nanowires. The extracted values are similar to state-of-the-art quantum dots within Si/SiGe and Si/SiO2 systems. [ABSTRACT FROM AUTHOR]

Radiation effects on graphene field effect transistors (GFETs) with hexagonal boron nitride (h-BN) thin film substrates are investigated using 60Co gamma-ray radiation. This study examines the radiation response using many samples with varying h-BN film thicknesses (1.6 and 20 nm thickness) and graphene channel lengths (5 and 10 μm). These samples were exposed to a total ionizing dose of approximately 1 Mrad(Si). I-V measurements were taken at fixed time intervals between irradiations and postirradiation. Dirac point voltage and current are extracted from the I-V measurements, as well as mobility, Dirac voltage hysteresis, and the total number of GFETs that remain properly operational. The results show a decrease in Dirac voltage during irradiation, with a rise of this voltage and permanent drop in Dirac current postirradiation. 1.6 nm h-BN substrate GFETs show an increase in mobility during irradiation, which drops back to preirradiation conditions in postirradiation measurements. Hysteretic changes to the Dirac voltage are the strongest during irradiation for the 20 nm thick h-BN substrate GFETs and after irradiation for the 1.6 nm thick h-BN GFETs. Failure rates were similar for most GFET types during irradiation; however, after irradiation, GFETs with 20 nm h-BN substrates experienced substantially more failures compared to 1.6 nm h-BN substrate GFETs. [ABSTRACT FROM AUTHOR]

We present a theoretical proposal for the design of a thermal switch based on the anisotropy of the thermal conductivity of PbTiO3 and the possibility to rotate the ferroelectric polarization with an external electric field. Our calculations are based on an iterative solution of the phonon Boltzmann Transport Equation and rely on interatomic force constants computed within an efficient second-principles density functional theory scheme. We also characterize the hysteresis cycle of the thermal conductivity in the presence of an applied electric field and show that the response time would be limited by the speed of the ferroelectric switch itself and thus the switch can operate in the high-frequency regime. [ABSTRACT FROM AUTHOR]