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Textured Poling of the Ferroelectric Dielectric Layer for Improved Organic Field-Effect Transistors
摘要： Polymer ferroelectrics are playing an increasingly active role in flexible memory application and wearable electronics. The relaxor ferroelectric dielectric, poly(vinylidene fluoride trifluorethylene (PVDF-TrFE), although vastly used in organic field-effect transistors (FETs), has issues with gate leakage current especially when the film thickness is below 500 nm. This work demonstrates a novel method of selective poling the dielectric layer. By using solution-processed 6,13-bis(triisopropylsilylethynyl)pentacene (TIPS-pentacene) as the organic semiconductor, it is shown that textured poling of the PVDF-TrFE layer dramatically improves FET properties compared to unpoled or uniformly poled ferroelectric films. The texturing is achieved by first vertically poling the PVDF-TrFE film and then laterally poling the dielectric layer close to the gate electrode. TIPS-pentacene FETs show on/off ratios of 105 and hole mobilities of 1 cm2 Vs?1 under ambient conditions with operating voltages well below ?5 V. The electric field distribution in the dielectric layer is simulated by using finite difference time domain methods.
关键词： poling,organic semiconductor,ferroelectric dielectric,field-effect transistors,transport
更新于2025-09-19 17:15:36
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Synthesis and investigation of structural, optical, dielectric and electronic properties of a new hybrid: [C13H21N2O2](Cd(SCN)3)
摘要： A new ferroelectric relaxor: [C13H21N2O2](Cd(SCN)3) procainium tris(thiocyanato) cadmiate(II) was synthesized and studied by single-crystal XRD. This compound crystallizes in the orthorhombic system with acentric space group Pna21. The crystal structure is formed of discrete ionic entities (C13H21N2O2)+ and [Cd(SCN)3]?. The cadmium atom has 3N3S hexa coordinated octahedral geometry. The sulfur atoms and the nitrogen atoms are in facial mode (fac). Each pair of cadmium atoms is triply bridged by μ-1,3-SCN–bridge. Consequently, a linear polymeric chain is formed. The procainium cations are bonded to these chains by hydrogen-bonding contacts and π–ring interaction. DSC measurement shows that this compound exhibits a diffuse ferro–paraelectric phase transition around 356 K. Dielectric study exhibits a relaxor behavior characterized by the transition temperature shifts toward higher temperature with the rise of frequency. This behavior was validated by the Vogel–Fulcher relationship and the modified Curie–Weiss law. The diffuseness parameter was γ = 1.96. The optical band gap Eg = 2.20 eV was estimated by diffuse reflection spectroscopy (DRS) investigation.
关键词： Ferroelectric relaxor,Structure,Conductivity,Modulus,Vogel–Fulcher model
更新于2025-09-19 17:15:36
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Switching dynamics and modeling of multi-domain Zr-Doped HfO2 ferroelectric thin films
摘要： HfO2-based ferroelectrics have attracted attention as promising materials for advanced memory applications owing to their negative capacitance effect, high scalability, and full-CMOS compatibility. Accordingly, the switching dynamics of HfO2 thin films have been actively discussed and simulated using the Landau-Khalatnikov equation (LK model). Although the simulated results agree with experimental results in many studies, there is a slight dissimilarity near the coercive field in the polarization-electric field curve. For accurate and general modeling, a new model that combines the conventional LK model and Euler's equation was proposed in this work. The model was examined under single-domain and multi-domain conditions. The simulated curves using the Landau-Euler method better fit with measured curves than those using the LK model.
关键词： polarization-electric field curve,HfO2,Switching dynamics,Ferroelectric
更新于2025-09-19 17:15:36
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[IEEE 2018 IEEE International Electron Devices Meeting (IEDM) - San Francisco, CA, USA (2018.12.1-2018.12.5)] 2018 IEEE International Electron Devices Meeting (IEDM) - Demonstration of High-speed Hysteresis-free Negative Capacitance in Ferroelectric Hf<inf>0.5</inf>Zr<inf>0.5</inf>O<inf>2</inf>
摘要： We report the experimental observation of hysteresis-free negative capacitance (NC) in thin ferroelectric Hf0.5Zr0.5O2 (HZO) films through high-speed pulsed charge-voltage measurements. Hysteretic switching is suppressed by the addition of thin Al2O3 layers on top of the HZO to prevent the screening of the polarization. We observe an S-shaped polarization-electric field dependence without hysteresis in agreement with Landau theory, which enables direct extraction of NC modeling parameters for ferroelectric HZO. Hysteresis-free NC is demonstrated down to 100 ns pulse widths limited only by our measurement setup. These results give critical insights into the physics of ferroelectric NC and practical NC device design using ferroelectric HZO.
关键词： hysteresis-free,Hf0.5Zr0.5O2,ferroelectric,negative capacitance,pulsed measurements,Landau theory
更新于2025-09-19 17:15:36
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Giant Piezoelectricity of Ternary Perovskite Ceramics at High Temperatures
摘要： Here, novel ferroelectric ceramics of (0.95 ? x)BiScO3-xPbTiO3-0.05Pb(Sn1/3Nb2/3)O3 (BS-xPT-PSN) of complex perovskite structure are reported with compositions near the morphotropic phase boundary (MPB), and which exhibit a piezoelectric coefficient d33 = 555 pC N?1, a large-signal coefficient *d33 ≈ 1200 pm V?1 at room temperature, and a high Curie temperature TC of 408 °C. More interestingly, this ternary system exhibits a giant and stable piezoelectric response at 200 °C with a large-signal *d33 ≈ 2500 pm V?1, matching that of the costly relaxor-based piezoelectric single crystals at room temperature. The mechanisms of such giant piezoelectricity and its characteristic temperature dependence are attributed to the spontaneous polarization rotation and extension under an electric field and the MPB-related phase transition. The findings reveal that the BS-xPT-PSN ceramics constitute a new family of high-performance piezoelectric materials suitable for electromechanical transducers that can be operated at high temperatures (at 200 °C, or higher).
关键词： giant piezoelectricity,relaxor ferroelectric,high temperatures
更新于2025-09-19 17:15:36
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Electroactive materials with tunable response based on block copolymer self-assembly
摘要： Ferroelectric polymers represent one of the key building blocks for the preparation of flexible electronic devices. However, their lack of functionality and ability to simply tune their ferroelectric response significantly diminishes the number of fields in which they can be applied. Here we report an effective way to introduce functionality in the structure of ferroelectric polymers while preserving ferroelectricity and to further tune the ferroelectric response by incorporating functional insulating polymer chains at the chain ends of ferroelectric polymer in the form of block copolymers. The block copolymer self-assembly into lamellar nanodomains allows confined crystallization of the ferroelectric polymer without hindering the crystallinity or chain conformation. The simple adjustment of block polarity leads to a significantly different switching behavior, from ferroelectric to antiferroelectric-like and linear dielectric. Given the simplicity and wide flexibility in designing molecular structure of incorporated blocks, this approach shows the vast potential for application in numerous fields.
关键词： Block copolymer self-assembly,Tunable response,Ferroelectric polymers,Electroactive materials
更新于2025-09-19 17:15:36
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Effects of B-Site Substitution on Up-Conversion Luminescence and Ferroelectric Properties in Er3+-Doped Strontium Barium Niobate
摘要： An effective route to regulate up-conversion luminescence (UCL) and polarization properties has been developed in tetragonal tungsten bronze ferroelectrics of (Sr0.29Er0.01)Ba0.7Nb2-xMoxO6 (SBN-Ax, 0 ≤ x ≤ 0.1) and Sr0.3Ba0.7(Nb1.99-xMoxEr0.01)O6 (SBN-Bx, 0 ≤ x ≤ 0.1) ceramics. Through investigating the UCL spectra of SBN-Ax and SBN-Bx ceramics, markedly different enhancement effects of UCL intensity have been revealed which can be attributed to the peculiar structural feature of TTBs. Furthermore, temperature sensing, dielectric and ferroelectric properties have also confirmed to display B-site substitution-dependent intriguing behaviors.
关键词： ferroelectric,luminescence,Ceramics
更新于2025-09-19 17:15:36
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Texture and phase variation of ALD PbTiO <sub/>3</sub> films crystallized by rapid thermal anneal
摘要： PbTiO3 (lead titanate) thin films were deposited by atomic layer deposition (ALD) and crystallized via rapid thermal anneal. The films were grown using lead bis(3-N,N-dimethyl-2-methyl-2-propanoxide) and tetrakis dimethylamino titanium as cation precursors. A combination of H2O and ozone was used as oxidizers. Phase-pure, stoichiometric PbTiO3 was confirmed using x-ray diffraction, Rutherford backscattering spectroscopy, and scanning transmission electron microscopy. Ferroelectric hysteresis loops obtained by patterning circular capacitors with areas of 4.92 × 10?4 cm2 indicate a Pmax = 48 μC/cm2, 2Pr = 60 μC/cm2, Ec1 = ?73 kV/cm, Ec2 = 125 kV/cm, and a leakage current density of 15 μA/cm2 at 138 kV/cm. Capacitance versus voltage measurements were used to obtain a maximum dielectric constant of 290 at 85 kV/cm and loss tangent under 4% tested in the range of ±275 kV/cm. ALD PbTiO3 grown with near-ideal cation ratios crystallized into randomly oriented perovskite grains when grown on a sputtered Pt-coated Si substrate. A variation of rapid thermal anneal temperatures, ramp rates, and nucleation layers was investigated and did not have a significant effect on perovskite grain orientation.
关键词： texture,ferroelectric,lead titanate,rapid thermal anneal,atomic layer deposition
更新于2025-09-19 17:15:36
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Suppressing depolarization by tail substitution in an organic supramolecular ferroelectric
摘要： Despite being very well established in the field of electro-optics, ferroelectric liquid crystals so far lacked interest from a ferroelectric device perspective due to a typically high operating temperature, a modest remnant polarization and/or poor polarization retention. Here, we experimentally demonstrate how simple structural modification of a prototypical ferroelectric liquid-crystal benzene-1,3,5-trisamide (BTA) – introduction of branched-tail substituents – results in materials with a wide operating temperature range and a data retention time of more than 10 years in thin-film solution-processed capacitor devices at room temperature. The observed differences between linear- and branched-tail compounds are analyzed using density functional theory (DFT) and molecular dynamics (MD) simulations. We conclude that morphological factors like improved packing quality and reduced disorder, rather than electrostatic interactions or intra/inter-columnar steric hindrance, underlay the superior properties of the branched-tailed BTAs. Synergistic effects upon blending of compounds with branched and linear side-chains can be used to further improve the materials’ characteristics.
关键词： liquid crystal,BTA,DFT,molecular dynamics,supramolecular,ferroelectric,polarization retention
更新于2025-09-19 17:15:36
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Large Piezoelectric Stability and Low Polarization Fatigue in 6Pb(Sc1/2Nb1/2)O3-70Pb(Mg1/3Nb2/3)O3-24PbTiO3 Crystals
摘要： The electrical properties and polarization fatigue of [001]-oriented 6Pb(Sc1/2Nb1/2)O3-70Pb(Mg1/3Nb2/3)O3-24PbTiO3 (6PSN-70PMN-24PT) crystals were investigated. Compared with binary Pb(Mg1/3Nb2/3)O3-PbTiO3 (PMN-PT) crystals, the ternary 6PSN-70PMN-24PT crystal showed a higher rhombohedral–tetragonal transition temperature (TR-T = 120°C) and a larger coercive field (Ec = 4 kV/cm). It was found that the piezoelectric constant (d33 ≈ 1200 pC/N) and electromechanical coupling coefficient (kt ≈ 61%) were weakly dependent on the thermal annealing temperature (Ta), maintaining over 90% of the original value at Ta < 120°C, indicating excellent piezoelectric thermal stability. Electric fatigue measurements showed that the ternary 6PSN-70PMN-24PT crystal exhibited slight fatigue characteristics below 105 bipolar cycles, while the binary PMN-PT crystal exhibited sudden polarization degradation when the cycle numbers were above 102 cycles. The improved fatigue stability for 6PSN-70PMN-24PT crystals was attributed to the large coercive field. The physical mechanisms of the enhanced coercive field and high transition temperature were discussed based on repulsive energy and polar domains.
关键词： piezoelectric stability,6PSN-70PMN-24PT,Ferroelectric crystal,fatigue
更新于2025-09-19 17:15:36