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Operation principle of bistable ferroelectric diode. (a) Schematic mechanism of injection barrier lowering and current injection. The ferroelectric, semiconductor and electrodes are indicated by blue, red, and gray planes, respectively. The top electrode at y = 120 nm is the injecting contact characterized by an injection barrier of 0.7 eV. The collecting bottom electrode at y = 0 nm is grounded. Blue and yellow arrows indicate electric fields and current flow, respectively. +/− indicate polarization charge. (b) Current density and (c) hole density (10log-scale) of a ferroelectric diode in the on-state.
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Memory is a prerequisite for many electronic devices. Organic non-volatile memory devices based on ferroelectricity are a promising approach towards the development of a low-cost memory technology based on a simple cross-bar array. In this review article we discuss the latest developments in this area with a focus on the most promising opto-electro...
Citations
... PVDF and its copolymers are well known for good piezoelectric properties, chemical resistiveness, biocompatibility, mechanical strength and easy processability over inorganic piezoelectric materials. The application of these materials includes mechanical energy harvesting, sensors, actuators and memory devices [15][16][17][18]. It is a semi-crystalline polymer with repeating monomer unit of (-CH 2 -CF 2 -) which crystallizes into mainly four crystalline phases of α, β, γ and δ [19][20][21]. ...
Metal halide perovskites (MHPs) are highly emerging materials for their applications in the field of photovoltaics and optoelectronics. However, beyond these applications, the MHPs have been proven to be excellent candidates for the fabrication of self-powered nanogenerators on their own or in conjunction with piezoelectric polymers such as poly(vinylidene-fluoride) (PVDF). More so, lead-free MHPs are the need of hour, which opens up the possibility of a sustainable future. Additionally, in piezoelectric composite films containing MHP, it is possible to utilize the coupling of photoexcitation, semiconducting and piezoelectric properties, which leads to the piezo-phototronic effect. Here, we report the fabrication of Cs2SnI6-PVDF (CSIP) composite, where the synthesis of Cs2SnI6 nanoparticles was realized in an in-situ approach. Notably, the Cs2SnI6 nanoparticles nucleates 100% electroactive β- and γ-phases in PVDF which gives rise to the intrinsic piezoelectric nature of the lead free composite film. Furthermore, to decipher the interfacial interaction between Cs2SnI6 and PVDF first principle DFT study was performed which unravels the non-bonding interaction between the Cs2SnI6 and PVDF. The piezo-phototronic effect was successfully realized in the CSIP film indicating its promising use in the piezotronics sensor. Moreover, the CSIP films were utilized as a piezoelectric nanogenerator, which shows superior piezoelectric output voltage of 9 V and current of 5 μA. It can also be utilized in human physiological signal monitoring, as well as a pressure sensor. Hence, the combined properties of semiconducting, photoexcitation and piezoelectricity in the CSIP films can be utilized in both mechanical energy harvesting and piezotronics sensing applications.
... Ferroelectric materials (FEM) are considered as a candidate material platform for achieving next-generation edge computing thanks to their minimized thickness and enhanced electrical control. FEM are also promising candidates for important applications, such as three-dimensional (3D) cross-point memories, 9,10 hardware-based neural networks, 11 in-memory computing, 12,13 as well as optical and optoelectronic devices, including optical waveguides 14 and piezoelectric sensors. 15 Ferroelectric (FE) memory operations, based on the reversible switching between one orientation state to another in a nitride/ oxide-based material, showing marked contrast in electrical resistivity, generally requires less energy and offers shorter switching times as well as larger maximum switching endurance. ...
The ever-increasing importance of applications based on machine-learning has driven the need to develop delicate energy-efficient electronic hardware. Compared to traditional von-Neumann architectures, which contain separate main-memory and storage units, nonvolatile edge computing utilizes the same device structure for data storage and rapid operations, therefore promising to decrease the energy costs of data-centered computing significantly. Although various research has focused on exploration of new device architectures, engineering material systems suitable for these device designs remains challenging. Ferroelectric materials (FEM) are leading contenders for these systems because of their excellent materials and electronic properties. Here, we demonstrate how the role of composition and distortion in structural signatures of FEM can be studied using density functional theory (DFT). The previously unreported origins of vacancies and distortions are revealed, and we show that the stable AlScN model with wurtzite structure is described by small/negligible vacancy concentrations and minimal localized distortions. Additionally, the low vacancy populations formed can be explained by the need to remove energetically-unfavorable anti-bonding Al–N and Sc–N interactions near the Fermi level. Theoretical studies elucidate a vacancy-facilitated decrease in leakage currents. These results provide deeper insights that can help to rationalize the design of next-generation low-power electronic systems.
... Nowadays, the range of ferroelectric applications is still widening, including gas sensing devices [6], photovoltaics [7][8][9], and medical implementations [10,11], which opens perspectives for the design and exploration of new materials. New ferroelectrics with suitable mechanical properties are desired, for example, for applications in all-organic, flexible, and large-area electronic devices [12][13][14][15]. The studies in this area are also motivated by regulations on environment and requirements of sustainable development. ...
Heavy-metal-free ferroelectrics are sought as environmentally compatible alternatives to commonly used inorganic oxides. Here, we demonstrate direct evidence of the ferroelectric properties of a hybrid organic-inorganic material, dimethylglycinium-dimethylglycine chloride. At room temperature, the compound crystallizes in the polar space group P21 and exhibits a switchable spontaneous polarization of 1.9 μC cm⁻². Ferroelectric properties are preserved in a wide temperature range up to about 401 K, where the crystal undergoes the transition to the paraelectric phase of the space group P21/c. The temperature-dependent single-crystal X-ray diffraction study and the calorimetric data indicate an order-disorder contribution to the transition mechanism, which is consistent with the critical slowing down of the dielectric relaxation observed near the Curie point. The spontaneous polarization results from ionic displacements that are induced by changes in the disordering of the dimeric cations. In the ferroelectric phase, the crystal exhibits remarkable piezoelectric activity. The electromechanical and elastic properties of the material were thoroughly characterized.
... 1−6 Mechanical flexibility also enables them for the emerging flexible/wearable electronics. However, only polymer ferroelectrics (PFs), i.e., poly(vinylidene fluoride) (PVDF) and its copolymer P(VDF-TrFE), 7,8 are intensely studied, which are significantly limited by their large coercive field (∼500 kV cm −1 ) and a relatively small spontaneous polarization P s (∼10 μC cm −2 ). Although, some novel molecular ferroelectrics (MFs) with excellent properties even comparable to their inorganic counterparts were revealed in the past decade, 9−13 MF-based micro/nanomemory devices and arrays for integrated device application are still rarely reported. ...
... Ferroelectric liquid crystalline (FLC) materials, that the spontaneous polarization can be reversed by applying of an external reverse electric field, can respond to desired properties for specific applications such as memory devices [19][20][21][22]. Ferroelectricity in calamitic LCs is formed through molecular chirality [23][24][25][26]. ...
The synthesis and mesomorphic properties of novel chiral imine-based rod-like molecules carrying a (S)-3,7-Dimethyloctyloxy unit and a n-decyloxy chain at terminals have been reported. Novel molecules, (S)-5-n-decyloxy-2-[[[4′-(3,7-dimethyloctyloxy)phenyl]imino]methyl]phenol (5) and (S)-4-n-decyloxybenzylidene-4′-(3,7-dimethyloctyloxy)aniline (6), differ from each other by the presence of a lateral hydroxy group on aryl aldehyde. The both structures have been identified by ¹H-NMR, ¹³C-NMR, FT-IR spectroscopy, and MS-QTOF. The mesomorphism of molecules have been investigated by optical polarizing microscopy as well as differential scanning calorimetry. The presence of a lateral hydroxy group leads to a notable mesophase stability up to 37 °C in the chiral tilted smectic (SmC*) mesophase interval as compared to imine analog 6 due to intramolecular hydrogen bonding. Therefore, the investigation of dielectric and impedance parameters as well as electro-optic behavior of chiral rod-like compound 5 derived from salicylaldimine-core have been carried out. The real and imaginary dielectric constant, conductivity mechanism, impedance, and dielectric relaxation mechanism of new chiral compound 5, exhibiting an enantiotropic SmC* mesophase which shows a ferroelectric switching with PS values in the range of 220–100 nC cm⁻², have been investigated in the frequency range between 100 rad/s and 10⁶ rad/s at different temperatures altering from 25 to 85 °C.
... Interestingly, the photovoltaic generation curve of thin BFPT films (Fig. 4e) resembles the charge and discharge of a capacitor component of RC circuits, attesting the ferroelectric capacitive behavior of the BFPT compound. In fact, ferroelectric compounds behave similarly to a capacitor [41]. Possibly, when photovoltaic electric charges are generated, they change the internal configurations of the electric fields, which act in the ordering of electrical dipoles and create additional power barriers to electron-hole recombination. ...
In this manuscript the multifunctional multiferroic 0.6BiFeO3-0.4PbTiO3 (BFPT) thin films are presented as an interesting alternative for multifunctional photovoltaic applications. The compound is chemically and structurally stable at high temperatures and consequently reliable to work under difficult operating conditions, such as sunlight radiation. Nanostructured single-phased BFPT thin films were processed and their electric, dielectric, structural, and optics properties were characterized in this work. The films were used as active layers in a heterostructured photovoltaic arrangement, which proves their photovoltaic behavior. Interesting physical properties, as intrinsic photovoltage production (~ 1 mV/cm2) with excitation power (300 W) were associated to the high dielectric constant (> 220 at 1 kHz and room temperature), the existence of long-range electrical conductivity processes, and the presence of two band gap energies (at 3.95 eV and 2.51 eV) in the BFPT compound that enhance the light absorption with consequent photovoltaic generation in the visible light region.
... 1−4 For example, ferroelectric materials possess a spontaneous electric polarization that can be switched in an electric field (Figure 1a). 4 Likewise, exciton separation in organic solar cells relies on reducing the exciton binding energy (E c = e 2 /4πε 0 εr), where e is the elementary charge, ε 0 is the permittivity of free space, ε is the permittivity, and r is the distance between charges). 5 The most effective way to reduce the Coulombic attraction between the donor and acceptor is by increasing ε of the surrounding medium ( Figure 1b). ...
The polarity of all-cis-multifluorinated cyclohexanes can be fine-tuned by the number and relative orientation of fluoro substituents, giving rise to a series of compounds with strong dipole moments. Simulations provided the energetics, the dipole moments, and the respective molecular polarizabilities, while dielectric spectroscopy gave information on the dielectric permittivities and the molecular dynamics. In special cases, dipole moments in excess of 6 D and dielectric permittivities of over 300 were obtained by simulation and experiment. Melting temperatures within a given family of multifluorinated cyclohexanes were found to scale with the molecular volume. The less-symmetric all-cis-octafluorotetrahydronaphthalene did not readily crystallize, permitting an investigation of the molecular dynamics in an energetically unfavorable yet rigid and facially polarized isomer. The resulting dynamics above the glass temperature conform to the structural α-relaxation and to the celebrated Johari-Goldstein β-relaxation.
... 77 In addition, certain ferroelectric materials can be solution-processed and adopted in an ultimate memory system. 78 Ferroelectric polymers, such as poly(vinylidene fluoride) (PVDF) and its copolymer with trifluoroethylene P(VDF-TrFE), have received much attention in memory devices. Guo et al. demonstrated a flexible ferroelectric random access memory (FeRAM) devices based on a self-assembly array of P(VDF-TrFE) lamellae. ...
Emerging flexible artificial sensory systems using neuromorphic electronics have been considered as a promising solution for processing massive data with low power consumption. The construction of artificial sensory systems with synaptic devices and sensing elements to mimic complicated sensing and processing in biological systems is a prerequisite for the realization. To realize high-efficiency neuromorphic sensory systems, the development of artificial flexible synapses with low power consumption and high-density integration is essential. Furthermore, the realization of efficient coupling between the sensing element and the synaptic device is crucial. This Review presents recent progress in the area of neuromorphic electronics for flexible artificial sensory systems. We focus on both the recent advances of artificial synapses, including device structures, mechanisms, and functions, and the design of intelligent, flexible perception systems based on synaptic devices. Additionally, key challenges and opportunities related to flexible artificial perception systems are examined, and potential solutions and suggestions are provided.
... Using lateral ferroelectric-semiconductor heterostructures, Fig. 1(d) addresses the orthogonality challenge wherein the ferroelectric phase provides bistability and the semiconductor phase provides conduction. 49 It has been demonstrated that thin-films prepared from a solution with blends of P(VDF-TrFE) and regio-irregular poly(3-hexylthiophene), rir-P3HT, in a common solvent, distilled tetrahydrofuran (THF), exhibit the desired phase separated structure of vertical rir-P3HT columns in the P(VDF-TrFE) matrix, as schematically shown in Fig. 3(a). The chemical structure of rir-P3HT is given in Fig. 4(a). ...
Developing new memory concepts and devices has been one of the most productive fields of research for the past decade. There is a need for a nonvolatile memory technology based on resistance switching. An ideal memory element is a bistable rectifying diode that enables realization of a simple crossbar memory array with highest areal bit density. Ferroelectrics have been suggested to code digital information due to their intrinsic and stable binary electronic polarization. However, realization of a ferroelectric bistable rectifying diode is challenging since ferroelectricity and electrical conductivity are mutually exclusive and cannot coexist in a single compound. As a solution, lateral ferroelectric-semiconductor heterostructures have been suggested for the realization of ferroelectric diodes. Bistable rectifying diodes and their respective nonvolatile crossbar memory arrays based on ferroelectric-semiconductor lateral heterostructures have been successfully demonstrated with organic ferroelectrics and organic semiconductors. The present review focuses on the resistance switching in ferroelectric-semiconductor heterostructure rectifying diodes based on polymers and discusses the latest developments over the last decade.
... Based on the definition of ferroelectrics, their functionality is the electric bistability that draws an (ideally rectangular) hysteric loop between the electric displacement (D) and field (E) curve; it can be used for data storage devices such as the ferroelectric random access memory (FeRAM) and ferroelectric field-effect transistor (FeFET). [3][4][5] Other important applications are the condenser and capacitor because the dielectric permittivity (ε) obeying the Curie-Weiss law is maximized during the paraelectric-ferroelectric phase transition at the Curie temperature (T c ). Many functionalities of ferroelectrics are based on cross-correlation phenomena. ...
