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Influence of charge accumulation at the grain boundary on the electrical behavior of a ferroelectric field-effect transistor
摘要： A phase field method was used to investigate the influence of charge accumulation at the grain boundary on the electrical behavior of a ferroelectric field-effect transistor containing a polycrystalline gate. Both the domain structure and the electrical behavior of the ferroelectric field-effect transistor were found to depend on the coefficient χ, which represents the charge accumulation at the grain boundary. With increasing χ, both the width of the memory window of the capacitance–voltage curves and the on-state source–drain current decreased, while the off-state source–drain current increased. This can be explained in terms of the weakening polarization effect in the grain interior owing to the presence of a built-in electric field caused by the accumulated charge at the grain boundary.
关键词： electrical behavior,charge accumulation,phase field method,grain boundary,ferroelectric field-effect transistor
更新于2025-09-09 09:28:46
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Reference Module in Materials Science and Materials Engineering || Liquid Crystals Under High Pressure
摘要： From a historical perspective, the first high pressure experiments were carried out soon after the discovery of liquid crystals, although the field became more active much later. Despite being considered as equivalent thermodynamic variables, temperature (T) and pressure (P) act differently on liquid crystals (LC), with the former affecting the rotational and vibration energy dependent parameters, and the latter altering the intermolecular distances. This feature, in combination with the fact that relatively low pressures bring about significant changes in the properties of LCs, has provided impetus for the studies described here. These investigations have not only augmented the knowledge on LCs obtained at atmospheric pressure, but have provided valuable insights into the understanding of complex fluids (Chandrasekhar and Shashidhar, 1979; Pollmann, 1999; Urban, 2014); the studies have been carried out using apparatus such as optical transmission, DTA, calorimetry, dielectric, NMR, XRD, volumetry, and Raman, detailed in these articles. For the description of the structures of the LC mesophases, numbering more than 40, the reader may refer to the article.
关键词： ferroelectric properties,mesomorphism,liquid crystals,nematic-isotropic transition,high pressure
更新于2025-09-09 09:28:46
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Manipulating the Ferroelectric Domain States and Structural Distortion in Epitaxial BiFeO3 Ultrathin Films via Bi Nonstoichiometry
摘要： Exploring and manipulating the domain configurations in ferroelectric thin films are of critical importance for the design and fabrication of ferroelectric heterostructures with novel functional performance. In this study, BiFeO3 (BFO) ultrathin films with various Bi/Fe ratios from Bi-excess to Bi-deficient have been grown on (La0.7Sr0.3)MnO3 (LSMO) covered SrTiO3 substrates by laser molecular beam epitaxy system. Atomic force microscopy and piezoresponse force microscopy measurements show that both the surface morphology and ferroelectric polarization of the films are relevant to the Bi nonstoichiometry. More significantly, the Bi-excess thin films show upward (from substrate to film surface) uniform ferroelectric polarization, while a Bi-deficient thin film exhibits downward uniform polarization, which means the as-grown polarization of the BFO thin films can be controlled by changing Bi contents. Atomic-scale structural and chemical characterizations and second harmonic generation measurements reveal that two different kinds of structural distortion and interface atomic configuration in the BFO/LSMO heterostructures can be induced by the change of Bi nonstoichiometry, leading to the two opposite as-grown ferroelectric polarizations. It has also been revealed that the band gap of the BFO thin films can be modulated via Bi nonstoichiometry. These results demonstrate that Bi nonstoichiometry plays a key role on the ferroelectric domain states and physical properties of BFO thin films, and also open a new avenue to manipulate the structure and ferroelectric domain states in BFO thin films.
关键词： BiFeO3 ultrathin films,interface atomic configuration,ferroelectric domain states,Bi nonstoichiometry,structural distortion
更新于2025-09-09 09:28:46
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Extraordinary dielectric properties at heterojunctions of amorphous ferroelectrics
摘要： Materials having a high dielectric constant are needed for a variety of electrical applications from transistors to capacitors. Ferroelectric amorphous-oxide (glass) alkali-ion electrolytes of composition A2.99Ba0.005ClO (A = Li, Na) are shown by two different types of measurement and different consistent analysis to have extraordinarily high dielectric constants varying from 109 at 25°C to 1010 at 220°C if the glass is properly conditioned. These anomalously high dielectric properties coexist with alkali-ion conductivities at 25°C that are equivalent to those of the best organic-liquid electrolytes of a Li-ion cell, and cyclic voltammetry (CV) in a Au/glass electrolyte/Au cell is stable from ?10 to +10 V. A model to interpret microscopically all the key features of the CV curves shows that the electric-double-layer capacitors (EDLCs) that form at the gold/electrolyte interfaces in the Au/glass electrolyte/Au heterojunction reverse polarization at an applied voltage V = ± 2.1 V resulting in three almost equivalent discharging capacitances for a single physical capacitor from -10 to +10 V.
关键词： amorphous-oxide,ferroelectric,alkali-ion electrolytes,dielectric constant,electric-double-layer capacitors,cyclic voltammetry
更新于2025-09-09 09:28:46
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Fractional effects on solitons in a 1D array of rectangular ferroelectric nanoparticles
摘要： In this paper, we present non-local effects on solitons in a one-dimensional (1D) array of ferroelectric nanoparticles. Using the discrete tangent hyperbolic method, several fractional function solutions are obtained such as fractional hyperbolic, trigonometric and rational function solutions. As results, we derive many solitons such as dark, bright and rogue waves. We show that the fractional parameter α has an effect on the width and on the amplitude of the above-obtained solitons. Their width and their amplitude are modified by the value of the fractional parameter α. Fractional derivative has a memory effect on ferroelectric nanoparticles. Applications of the obtained results are also presented.
关键词： Ferroelectric nanoparticles,discrete tangent hyperbolic method,fractional effect,solitons
更新于2025-09-09 09:28:46
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A Novel Study: The Effect of Graphene Oxide on the Morphology, Crystal Structure, Optical and Electrical Properties of Lanthanum Ferrite Based Nano Electroceramics Synthesized by Hydrothermal Method
摘要： Lanthanum Ferrite based nanocomposites were prepared with various Graphene oxide contents by the hydrothermal method. The crystalline structure, morphological properties, electrical and optical properties of samples were investigated. X-ray diffraction results indicate that all the nano electroceramics are polycrystalline with an Orthorhombic structure. Results from scanning and transmission electron microscopes indicate that the Bismuth ferrite/Graphene oxide powders have nanostructure. The optical band gaps of the nano electroceramics were calculated for the various amount of Graphene oxide. The electrical properties of samples were investigated with the temperature depend on conductivity measurements. The measurement shows that the electrical conductivity changes with increasing temperature and graphene oxide dopants of all samples. Activation energy values of the nanocomposites decrease with increasing graphene oxide content. The dielectric properties of Lanthanum Ferrite/Graphene Oxide nanocomposites (real and imaginer) with respect to frequency variation (1 KHz–5 MHz) were measured at room temperature. The relative permittivity, dielectric loss and alternating current conductivity values of the samples were estimated. It is show that relative permittivity, dielectric loss and alternating current conductivity increase with increasing frequency. The polarization-electric field hysteresis loop of all Lanthanum Ferrite/Graphene Oxide nano electroceramics was measured at the room temperature. The loop shows proper saturation with enhanced saturation polarization and coercive electric field. The obtained findings suggest that the physical and electrical properties of Lanthanum Ferrite/Graphene Oxide nano electroceramics can be changed by Graphene Oxide doping. These materials can be used for a variety of technological applications in the field of dielectric and ferroelectric.
关键词： Dielectric Properties,Graphene Oxide,Lanthanum Ferrite,Ferroelectric,Hydrothermal Method
更新于2025-09-09 09:28:46
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Polarization-Direction Dependence of Thermodynamic Stability of Ferroelectric BiAlO <sub/>3</sub> (0001) Polar Surfaces
摘要： Polar surfaces of ferroelectric oxides are of great importance for both fundamental and practical interest. In this report, we present a theoretical study to determine the thermodynamic stability and electronic properties of ferroelectric BiAlO3(0001) surfaces. According to the calculated surface phase diagram, we predict that the equilibrium stoichiometries are distinct for the oppositely polarized BiAlO3 surfaces under the same chemical conditions. In addition to nonstoichiometry of the surface chemical compositions, we find that anomalous filling of the surface states can also result in surface metallization in order to compensate the remarkable surface polarity. Besides providing atomic-scale understanding of the BiAlO3(0001) surfaces, we also put forward the practical implications in novel magnetoelectric devices and advanced surface chemistry.
关键词： Magnetoelectric devices,Surface chemistry,Thermodynamic stability,Surface metallization,BiAlO3(0001) surfaces,Electronic properties,Ferroelectric oxides
更新于2025-09-09 09:28:46
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Recent Advances in Ferroelectric Nanosensors: Toward Sensitive Detection of Gas, Mechanothermal Signals, and Radiation
摘要： A spontaneous polarization that occurs below the Curie temperature is characteristic for ferroelectric materials. This polarization is sensitive to many external conditions such as an electric field, mechanical deformation, temperature, and chemical and biological factors. Therefore, bulk ferroelectric materials have been used for decades in sensors and actuators. Recently, special attention has been paid to ferroelectric nanostructures that represent better sensing properties than their bulk counterparts. This paper presents a comprehensive survey of applications of nanoferroelectrics in different types of sensors, e.g., gas sensors and piezoelectric, pyroelectric, and piezoresistive sensors of mechanothermal signals, as well as photodetectors, ionizing radiation detectors, and biosensors. The recent achievements and challenges in these fields are summarized. This review also outlines the prospects for future development of sensors based on nanosized ferroelectrics.
关键词： gas detection,ferroelectric,nanosensors,mechanothermal signals,radiation detection,biosensors
更新于2025-09-09 09:28:46
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Unveiling the dual role of chemically synthesized copper doped zinc oxide for resistive switching applications
摘要： In this study, efforts were devoted to unveiling the dual role of single crystalline Cu (5%) doped ZnO (Cu:ZnO) synthesized by a simple and low-cost chemical process and to investigate its efficacy on resistive switching (RS) applications. It was found that when Cu:ZnO was annealed at a lower temperature of 450 °C and integrated onto ITO/glass for RS applications, only oxygen mediated vacancies were responsible for its resistive switching. However, ferroelectric properties have been observed when the same Cu:ZnO was annealed at a higher temperature of 800 °C and integrated onto Nb doped SrTiO3. X-ray diffraction, high resolution transmission electron microscope, x-ray photoelectron spectroscopy, UV-VIS-near infrared spectrometer, and piezoelectric force microscopy (PFM) were employed to study the crystallinity, interfaces, chemical compositions, bandgap, and domains in Cu:ZnO thin films, respectively. The bandgap of Cu:ZnO was found to be 3.20 eV. PFM study exhibits the domain inversion with 180° polarization inversion by applying an external bias, evidencing its effectiveness for memory applications. When the electrical characteristics were concerned, the RS device based on this ferroelectric Cu:ZnO offers better performance, such as lower SET/RESET voltages (～1.40 V), higher retention (up to 106 s) without distortion, and higher ON/OFF ratio (2.20 × 103), as compared to the former lower temperature annealed Cu:ZnO devices. A band-diagram was proposed, and transport studies were developed to understand the operational mechanism of these devices. This study explains both the limits and scopes of Cu:ZnO RS devices and formulates an idea which may accelerate the design of future generation devices.
关键词： copper doped zinc oxide,memory applications,band-diagram,resistive switching,ferroelectric properties
更新于2025-09-09 09:28:46
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Structure Analysis and Ferroelectric Response of Bi <sub/>0.5</sub> Na <sub/>0.5</sub> TiO <sub/>3</sub> Nanopowder Synthesized by Sol–Gel Method
摘要： In this work, bismuth sodium titanate, Bi0(cid:2)5 ± xNa0(cid:2)5 ± y TiO3 (BNT, x(cid:3) y = ?0(cid:2)05–0.08) nanopowders were produced using the low-temperature sol–gel technique. The effects of de?cient and excess amounts of Bi and Na on BNT structure were systemically examined through X-ray powder diffraction (XRD), energy dispersive analysis (EDS) and scanning electron microscope (SEM). The optimized composition of the BNT nanopowder was pelletized and sintered at different temperatures (950 (cid:3)C–1150 (cid:3)C). Highly dense ceramics possessing pure perovskite phase was observed for the sample sintered at an optimum sintering temperature (1100 (cid:3)C). The ferroelectric properties were found to increase with an increase in sintering temperature up to 1100 (cid:3)C and then decrease. This study justi?es that Bi and Na non-stoichiometry (proper excess), processing and sintering temperatures play important role in the successful synthesis of BNT ceramics.
关键词： Nanopowders,Sol–Gel,Ferroelectric,Calcination Temperature
更新于2025-09-09 09:28:46