Ferroelectric Polarization Field Research Articles

The multifield regulation on resistance of PbPd0.9Co0.1O2/PMN-PT(001) laminate film

Spin gapless semiconductor (SGS) presents abundant electric and magnetic properties and is highly sensitive to external factors, such as current, electric field, magnetic field, and stress. This paper reports on a PbPd0.9Co0.1O2/PMNPT(001) laminate thin film with the “SGS/ferroelectrics” structure, which exhibits significant current-induced resistance (I-ER) effect. More importantly, the colossal static electric-field-induced resistance (E-ER) effect in such a laminate film was observed for the first time. The introduction of lattice defects (Pb vacancies) induces a local electric field, electron spin ordering state, and ferroelectric polarization field effect to explain the excellent physical properties. The reported laminate thin film composite exhibits promising application potential in spintronic devices, composite sensor units, storage systems, and other low-energy semiconductor electronic device fields. This work proposes an alternative way to investigate the novel properties for spin gapless semiconductors and expand the research fields of multi-field modulation effect in magnetoelectric composites.

Ferroelectric-Optoelectronic Hybrid System for Photodetection.

Photodetectors (PDs), as functional devices based on photon-to-electron conversion, are an indispensable component for the next-generation Internet of Things system. The research of advanced and efficient PDs that meet the diverse demands is becoming a major task. Ferroelectric materials can develop a unique spontaneous polarization due to the symmetry-breaking of the unit cell, which is switchable under an external electric field. Ferroelectric polarization field has the intrinsic characteristics of non-volatilization and rewritability. Introducing ferroelectrics to effectively manipulate the band bending and carrier transport can be non-destructive and controllable in the ferroelectric-optoelectronic hybrid systems. Hence, ferroelectric integration offers a promising strategy for high-performance photoelectric detection. This paper reviews the fundamentals of optoelectronic and ferroelectric materials, and their interactions in hybrid photodetection systems. The first section introduces the characteristics and applications of typical optoelectronic and ferroelectric materials. Then, the interplay mechanisms, modulation effects, and typical device structures of ferroelectric-optoelectronic hybrid systems are discussed. Finally, in summary and perspective section, the progress of ferroelectrics integrated PDs is summed up and the challenges of ferroelectrics in the field of optoelectronics are considered.

Ferroelectric field effect transistors for electronics and optoelectronics

Ferroelectric materials have shown great value in the modern semiconductor industry and are considered important function materials due to their high dielectric constant and tunable spontaneous polarization. A ferroelectric field effect transistor (FeFET) is a field effect transistor (FET) with ferroelectric polarization field introduced to regulate carriers in semiconductors. With the coupling of ferroelectric and semiconductor, FeFETs are attractive for advanced electronic and optoelectronic applications, including emerging memories, artificial neural networks, high-performance photodetectors, and smart sensors. In this review, representative research results of FeFETs are reviewed from the perspective of structures and applications. Here, the background and significance of ferroelectrics and FeFETs are given. Furthermore, methods of building FeFETs in different structures and physical models describing the characteristics of FeFET are introduced. Important applications of FeFETs in electronics and optoelectronics are presented, with a comparison of performance between FeFETs and FETs without ferroelectrics, including memories and memristive devices, photodetectors, negative capacitance FETs, sensors, and multifunctional devices. Finally, based on the above discussions, promising applications and challenges of FeFETs are summarized.

Highly sensitive photodetector based on two-dimensional ferroelectric semiconducting β-InSe/graphene heterostructure

A 2D ferroelectric β-InSe/graphene heterostructure was fabricated by mechanical exfoliation, and the carrier dynamics crossing the heterostructure interface has been systematically investigated by Raman, photoluminescence, and transient absorption measurements. Due to the efficient interfacial photo excited electron transfer and photogating effect from trapped holes, the heterostructure devices demonstrate superior performance with a maximum responsivity of 2.12 × 104 A W−1, detectivity of 1.73 × 1014 Jones, and fast response time (241 μs) under λ = 532 nm laser illumination. Furthermore, the photo responses influenced by the ferroelectric polarization field are investigated. Our work confirms a ferroelectric β-InSe/graphene heterostructure as an outstanding material platform for sensitive optoelectronic applications.

Ferroelectricity enhanced self-powered solar-blind UV photodetector based on Ga2O3/ZnO:V heterojunction

Ferroelectric materials with spontaneous polarization can change the direction of the depolarizing field by applying the external electric field, showing great potential in regulating the photoelectric process. In this work, self-powered solar-blind ultraviolet (UV) photodetectors (PDs) based on Ga2O3/ZnO:V heterojunction were fabricated by the pulsed laser deposition method. The photoresponse behaviors of the Ga2O3/ZnO:V PDs can be modulated by the induced ferroelectric polarization field in ZnO:V. In the downward poling state, the Ga2O3/ZnO:V PD showed a responsivity of 95.53 mA/W and a detectivity of 1.18 × 1012 Jones to 260 nm light, which were 3.2 times higher than that of the unpoled state. Moreover, the rise/decay time was shortened from 10.3 μs/1.76 ms to 6.2 μs/0.43 ms. The improved performance of the Ga2O3/ZnO:V PD had been attributed to the increase of the built-in electric field and the widening of the depletion region under the influence of the depolarization field, which could be beneficial to the separation and transport of photogenerated carriers at the heterojunction interface. This work could be of great value for the design and fabrication of ferroelectricity-enhanced self-powered UV photodetectors.

High-Performance Photocatalytic Reduction of Nitrogen to Ammonia Driven by Oxygen Vacancy and Ferroelectric Polarization Field of SrBi4 Ti4 O15 Nanosheets.

Photo-responsive semiconductors can facilitate nitrogen activation and ammonia production, but the high recombination rate of photogenerated carriers represents a significant barrier. Ferroelectric photocatalysts show great promise in overcoming this challenge. Herein, by adopting a low-temperature hydrothermal procedure with varying concentrations of glyoxal as the reducing agent, oxygen vacancies (Vo) are effectively produced on the surface of ferroelectric SrBi4 Ti4 O15 (SBTO) nanosheets, which leads to a considerable increase in photocatalytic activity toward nitrogen fixation under simulated solar light with an ammonia production rate of 53.41µmol g-1 h-1 , without the need of sacrificial agents or photosensitizers. This is ascribed to oxygen vacancies that markedly enhance the self-polarization and internal electric field of ferroelectric SBTO, and hence, facilitate the separation of photogenerated charge carriers and light trapping as well as N2 adsorption and activation, as compared to pristine SBTO. Consistent results are obtained in theoretical studies. Results from this study highlight the significance of surface oxygen vacancies in enhancing the performance of photocatalytic nitrogen fixation by ferroelectric catalysts.

Insight into the effect of pH on the ferroelectric polarization field applied in photoelectrochemical water oxidation

The polarization field of ferroelectric materials can increase the performance of a photoelectrode by manipulating the band bending at the solid-liquid interface. However, the effect of pH of an electrolyte to the ferroelectric polarization field when applied to photoelectrochemical water oxidation is still not clear. In this work, hematite and tetragonal barium titanate nanoparticles are synthesized to construct a ferroelectric-semiconductor hybrid photoanode. We find that the photocurrent density of the positive polarized photoanode is improved about 30% in the near neutral electrolyte. However, this effect is disappeared in the high pH electrolyte. The ferroelectric polarization field is beneficial to improve the surface states and the donor density in the space charge layer of the photoanode to enhance the hole collection ability and the water oxidation kinetics in a near neutral electrolyte. Through the molecular dynamic simulation, we find that the adsorption capacity of OH− groups on the polarized barium titanate is reduced at high pH value, thus weakens the impact of the ferroelectric polarization field. Our work can maximize the utilization of the ferroelectric materials by selecting the pH value of the electrolyte and provides a new insight into the mechanism of ferroelectrics on photoelectrochemical reactions.

High-detectivity tin disulfide nanowire photodetectors with manipulation of localized ferroelectric polarization field

Abstract Tin sulfide semiconductor nanowires (NWs) have been widely investigated for photodetection applications because of their good optical and electrical properties. Herein, we synthesized n-type SnS2 NWs and then fabricated SnS2 NW photodetectors with a ferroelectric polymer side-gate. The strong electric field induced by ferroelectric polymer can effectively suppress the dark current and improve the detectivity in SnS2 NW photodetectors. The photodetectors after polarization depletion exhibit a high photoconductive gain of 4.0 × 105 and a high responsivity of 2.1 × 105 A W−1. Compared with devices without polarization depletion, the detectivity of polarization-depleted photodetectors is improved by at least two orders of magnitude, and the highest detectivity is 1.3 × 1016 Jones. Further, the rise and fall time are 56 and 91 ms respectively, which are about tens of times faster than those without polarization depletion. The device also shows a good spectral response from ultraviolet to near-infrared. This study demonstrates that ferroelectric materials can enhance optoelectronic properties of low-dimensional semiconductors for high-performance photodetectors.

Effect of ferroelectric polarization field on different carrier migration in photoanode

Spontaneous polarization field in ferroelectric can improve the oxidation kinetics and photocurrent of a photoanode in photoelectrochemical water splitting. But the impact of ferroelectric polarization field on the migration of different charge carriers which have different mobility and diffusion length is still unknown. In this work, we synthesized tetragonal BaTiO3 nanoparticles by solvothermal method successfully and fabricated the hybrid photoanode composed by monoclinic WO3 and BaTiO3 for solar water oxidation. Density functional theory calculations showed that the mobility of electron was faster than that of the hole in WO3, and had a longer diffusion length. We demonstrated that the polarization field of ferroelectric had a greatly impact upon holes migration compared with electrons, thus the thin hybrid photoanode after poling by bias presented a significant improvement of photocurrent (210.5%) under the back-side illumination, and a remarkable augment of charge separation efficiency (94%) and oxidation kinetics (69%) at 1.23 V. Our work provided a deeper understanding of how ferroelectric polarization field affected the photoelectrochemical water oxidation and a general pathway towards enhancing minority carrier collection in photoanode.

Hafnium-zirconium oxide interface models with a semiconductor and metal for ferroelectric devices.

Density functional theory (DFT) is employed to investigate ferroelectric (FE) hafnium–zirconium oxide stack models for both metal–insulator–metal (MIM) and metal–insulator–semiconductor (MIS) structures. The role of dielectric (DE) interlayers at the ferroelectric interfaces with metals and semiconductors and the effects of thickness scaling of FE and DE layers were investigated using atomic stack models. A high internal field is induced in the FE and DE layers by the FE polarization field which can promote defect generation leading to limited endurance. It is also shown that device operation will be adversely affected by too thick DE interlayers due to high operating voltage. These DFT models elucidate the underlying mechanisms of the lower endurance in experimental MIS devices compared to MIM devices and provide insights into the fundamental mechanisms at the interfaces.

High nonvolatile modulation of resistance on a ferroelectric PbZr0·2Ti0·8O3 /Nd0.3Sm0.25Sr0·45MnO3 liquid-gated electric-double-layer transistors

Abstracts A ferroelectric polarization field electric-double-layer transistor based on the PbZr0·2Ti0·8O3 (PZT)/Nd0.3Sm0.25Sr0·45MnO3 (NSSMO) structure gated by ionic-liquid was established. The electrostatic modulation on the NSSMO channel was performed by applying electric field, while the respective non-volatile field effect upon the polarization field of PZT was investigated. Interestingly, a nonvolatile modulation on the resistance of NSSMO channel was observed, depending on the ferroelectric polarization field from PZT layer. Moreover, a large modulation of electrical conductivity of the NSSMO channel was achieved when applying a bias voltage of +3 V. This result indicates that a high nonvolatile electrostatic effect can be achieved in complex oxides devices under ferroelectric polarization field.

Enhanced carrier separation in ferroelectric In2Se3/MoS2 van der Waals heterostructure

Enhanced carrier separation in ferroelectric In2Se3/MoS2 van der Waals heterostructure and external electric field effects.

Multimechanism Synergistic Photodetectors with Ultrabroad Spectrum Response from 375 nm to 10 µm.

Broadening the spectral range of photodetectors is an essential topic in photonics. Traditional photodetectors are widely used; however, the realization of ultrabroad spectrum photodetectors remains a challenge. Here, a photodetector constructed by a hybrid quasi‐freestanding structure of organic ferroelectric poly(vinylidene fluoride–trifluoroethylene) (P(VDF‐TrFE)) with molybdenum disulfide (MoS2) is demonstrated. The 2D MoS2 with the ultrathin structure brings a great benefit of heat dissipation for the pyroelectric infrared detector. By coupling the mechanisms of pyroelectrics, photoconductor, and phototransistor effect, an ultrabroad spectrum response ranging from ultraviolet (375 nm) to long‐wavelength infrared (10 µm) is achieved. In the 2.76–10 µm spectral range, the 2D MoS2 is used to read and amplify the photocurrent induced by the pyroelectric effect of P(VDF‐TrFE). The sensitivity of the device in this spectral range is greatly enhanced. A high responsivity of 140 mA W−1, an on/off photocurrent switching ratio up to 103, and a quick response of 5.5 ms are achieved. Moreover, the ferroelectric polarization field dramatically enhances the photoconductive properties of MoS2 and restrains dark current and noise. This approach constitutes a reliable route toward realizing high‐performance photodetectors with a remarkable ultrabroad spectrum response, high responsivity, low power consumption, and room‐temperature operation.

Polarization-induced selective growth of Au islands on single-domain ferroelectric PbTiO3 nanoplates with enhanced photocatalytic activity

In this work, heterostructured Au@PbTiO3 nanoplates were synthesized successfully via a simple hydrothermal process. It is revealed that Au islands with the size of 8–20 nm selectively deposited on the positively polarized surface of the single-crystal and single-domain PbTiO3 nonaplates. The composite demonstrates an efficient photocatalytic performance toward degradation of Rhodamine B (RhB) solution under UV light. The possible mechanism is that the ferroelectric polarization efficiently separates the photogenerated electrons and holes and reduces the recombination of them. Then, the ferroelectric polarization field urged the electrons concentrated on the positively polarized surface and then transformed oxygen into superoxide radicals to enhance the photocatalytic activity. Recycled activity tests show that the heterostructured Au@PbTiO3 nanoplates would inhibit the photocorrosion behavior and provide high stability.

Graphene Dirac point tuned by ferroelectric polarization field

Graphene has received numerous attention for future nanoelectronics and optoelectronics. The Dirac point is a key parameter of graphene that provides information about its carrier properties. There are lots of methods to tune the Dirac point of graphene, such as chemical doping, impurities, defects, and disorder. In this study, we report a different approach to tune the Dirac point of graphene using a ferroelectric polarization field. The Dirac point can be adjusted to near the ferroelectric coercive voltage regardless its original position. We have ensured this phenomenon by temperature-dependent experiments, and analyzed its mechanism with the theory of impurity correlation in graphene. Additionally, with the modulation of ferroelectric polymer, the current on/off ratio and mobility of graphene transistor both have been improved. This work provides an effective method to tune the Dirac point of graphene, which can be readily used to configure functional devices such as p–n junctions and inverters.

Effects of Pb(Zr0.52Ti0.48)O3 polarization on the YBa2Cu3O7−x electrical transport and magnetization

The YBa2Cu3O7−x (YBCO) superconducting film of 70 nm thickness was prepared on a LaAlO3 (LAO) substrate via the sol–gel method, following which the Pb(Zr0.52Ti0.48)O3 (PZT) ferroelectric film possessing interfacial coherent structure was grown via pulsed laser deposition (PLD) method, and then the Pt top electrode was deposited onto the PZT film by DC sputtering, resulting in the Pt/PZT/YBCO tri-layer structure. The ferroelectric hysteresis characteristics and the effects of ferroelectric polarization field of PZT on the electrical properties and magnetization of YBCO were studied for the temperature range of 50–300 K. Results reveal that as the temperature decreases, the remanent polarization of Pt/PZT/YBCO remains nearly constant, while the coercive field increased. The R–T curve of YBCO shifts upwards (positive polarization) or downwards (negative polarization) due to the influence of PZT polarization, indicating that the ferroelectric polarization of PZT modulates the R–T curve of YBCO. When YBCO is in the superconducting state, the magnetization of YBCO decreases with increasing polarization of PZT, indicating that the polarization field of PZT has a modulation effect on the magnetization of YBCO. Further investigation on the J–V curve of Pt/PZT/YBCO revealed a threshold conduction voltage (Vt) and when the applied bias voltage was lower than Vt, the leakage current of Pt/PZT/YBCO was small, and when the applied voltage was higher than Vt, the leakage current rapidly increased. Meanwhile, the Vt increased with decreasing temperature and then markedly changes at the superconducting transition temperature of YBCO.

Ferroelectricity-modulated resistive switching in Pt/Si:HfO2/HfO2−x/Pt memory**Project supported by the National Natural Science Foundation of China (No. 11374182), the Natural Science Foundation of Shandong Province (No. ZR2012FQ012), and the Jinan Independent Innovation Projects of Universities (No. 201303019).

It is investigated for the effect of a ferroelectric Si:HfO2 thin film on the resistive switching in a stacked Pt/Si:HfO2/highly-oxygen-deficient HfO2−x/Pt structure. Improved resistance performance was observed. It was concluded that the observed resistive switching behavior was related to the modulation of the width and height of a depletion barrier in the HfO2−x layer, which was caused by the Si:HfO2 ferroelectric polarization field effect. Reliable switching reproducibility and long data retention were observed in these memory cells, suggesting their great potential in non-volatile memories applications with full compatibility and simplicity.

Ferroelectric Single-Crystal Gated Graphene/Hexagonal-BN/Ferroelectric Field-Effect Transistor.

The effect of a ferroelectric polarization field on the charge transport in a two-dimensional (2D) material was examined using a graphene monolayer on a hexagonal boron nitride (hBN) field-effect transistor (FET) fabricated using a ferroelectric single-crystal substrate, (1-x)[Pb(Mg1/3Nb2/3)O3]-x[PbTiO3] (PMN-PT). In this configuration, the intrinsic properties of graphene were preserved with the use of an hBN flake, and the influence of the polarization field from PMN-PT could be distinguished. During a wide-range gate-voltage (VG) sweep, a sharp inversion of the spontaneous polarization affected the graphene channel conductance asymmetrically as well as an antihysteretic behavior. Additionally, a transition from antihysteresis to normal ferroelectric hysteresis occurred, depending on the V(G) sweep range relative to the ferroelectric coercive field. We developed a model to interpret the complex coupling among antihysteresis, current saturation, and sudden conductance variation in relation with the ferroelectric switching and the polarization-assisted charge trapping, which can be generalized to explain the combination of 2D structured materials with ferroelectrics.

Ferroelectricity-induced resistive switching in Pb(Zr0.52Ti0.48)O3/Pr0.7Ca0.3MnO3/Nb-doped SrTiO3 epitaxial heterostructure

We investigated the effect of a ferroelectric Pb(Zr0.52Ti0.48)O3 (PZT) thin film on the generation of resistive switching in a stacked Pr0.7Ca0.3MnO3 (PCMO)/Nb-doped SrTiO3 (Nb:STO) heterostructure forming a p-n junction. To promote the ferroelectric effect, the thin PZT active layer was deposited on an epitaxially grown p-type PCMO film on a lattice-matched n-type Nb:STO single crystal. It was concluded that the observed resistive switching behavior in the all-perovskite Pt/PZT/PCMO/Nb:STO heterostructure was related to the modulation of PCMO/Nb:STO p-n junction’s depletion width, which was caused either by the PZT ferroelectric polarization field effect, the electrochemical drift of oxygen ions under an electric field, or both simultaneously.

Ferroelectric-field-induced spin-pinning effect in Pb(Zr0.5Ti0.5)O3∕La0.9Sr0.1MnO3 bilayers

The magnetic properties of Pb(Zr0.5Ti0.5)O3∕La0.9Sr0.1MnO3 bilayers epitaxially grown on Nb-doped SrTiO3 (001) substrate were studied. Bilayers with a fixed Pb(Zr0.5Ti0.5)O3 (PZT) layer thickness of 200nm and different La1−xSrxMnO3 layer thicknesses varying from 10to40nm show a divergence between field-cooled (FC) and zero-field-cooled (ZFC) temperature-dependent magnetization measurements. Moreover, the polarization state of the PZT ferroelectric layer induces a spin-pinning effect causing a variation of the M∕M(10K) ratio in ZFC measurement and the divergent temperature (Td) between FC and ZFC processes. The magnetic hysteresis loops measured in FC and ZFC processes confirm the spin-pinning effect induced from the ferroelectric polarization field, leading to an alternation of the hysteresis loop characteristics for samples polarized with different signs of voltage.