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The properties of ferroelectric materials, which were discovered almost a century ago 1 , have led to a huge range of applications, such as digital information storage 2 , pyroelectric energy conversion 3 and neuromorphic computing 4 , 5 . Recently, it was shown that ferroelectrics can have negative capacitance 6 – 11 , which could improve the energy efficiency of conventional electronics beyond fundamental limits 12 – 14 . In Landau–Ginzburg–Devonshire theory 15 – 17 , this negative capacitance is directly related to the double-well shape of the ferroelectric polarization–energy landscape, which was thought for more than 70 years to be inaccessible to experiments 18 . Here we report electrical measurements of the intrinsic double-well energy landscape in a thin layer of ferroelectric Hf 0.5 Zr 0.5 O 2 . To achieve this, we integrated the ferroelectric into a heterostructure capacitor with a second dielectric layer to prevent immediate screening of polarization charges during switching. These results show that negative capacitance has its origin in the energy barrier in a double-well landscape. Furthermore, we demonstrate that ferroelectric negative capacitance can be fast and hysteresis-free, which is important for prospective applications 19 . In addition, the Hf 0.5 Zr 0.5 O 2 used in this work is currently the most industry-relevant ferroelectric material, because both HfO 2 and ZrO 2 thin films are already used in everyday electronics 20 . This could lead to fast adoption of negative capacitance effects in future products with markedly improved energy efficiency. A ferroelectric thin film that behaves as a single domain is found to exhibit both negative capacitance and the predicted double-well polarization–energy relationship.

Negative capacitance is a newly discovered state of ferroelectric materials that holds promise for electronics applications by exploiting a region of thermodynamic space that is normally not accessible 1 – 14 . Although existing reports of negative capacitance substantiate the importance of this phenomenon, they have focused on its macroscale manifestation. These manifestations demonstrate possible uses of steady-state negative capacitance—for example, enhancing the capacitance of a ferroelectric–dielectric heterostructure 4 , 7 , 14 or improving the subthreshold swing of a transistor 8 – 12 . Yet they constitute only indirect measurements of the local state of negative capacitance in which the ferroelectric resides. Spatial mapping of this phenomenon would help its understanding at a microscopic scale and also help to achieve optimal design of devices with potential technological applications. Here we demonstrate a direct measurement of steady-state negative capacitance in a ferroelectric–dielectric heterostructure. We use electron microscopy complemented by phase-field and first-principles-based (second-principles) simulations in SrTiO 3 /PbTiO 3 superlattices to directly determine, with atomic resolution, the local regions in the ferroelectric material where a state of negative capacitance is stabilized. Simultaneous vector mapping of atomic displacements (related to a complex pattern in the polarization field), in conjunction with reconstruction of the local electric field, identify the negative capacitance regions as those with higher energy density and larger polarizability: the domain walls where the polarization is suppressed. Imaging steady-state negative capacitance in SrTiO 3 /PbTiO 3 superlattices with atomic resolution provides solid microscale support for this phenomenon.

In this letter, we demonstrate an efficient non‐volatile Boolean logic based on a single Schottky barrier and ferroelectric FinFET (SB‐Fe FinFETs) has been proposed and experimentally demonstrated. Ferroelectric HZO and metallic source and drain (MSD) were adopted r for non‐volatile and ambipolar characteristics on the devices. Benefiting from the designed multi‐level reading operation and the non‐volatile ambipolar characteristics, complete Boolean logic functions have been demonstrated on single SB‐Fe FinFET. Furthermore, thanks to the single gate pulse for both input B and read operation, all Boolean logic functions can be implemented in two steps. Robust output current and high speed for the logic functions are identified in the experimental results, indicating the technology promising for future logic‐in‐memory applications. In this letter, benefiting from the designed computing operation method and the metallic source and drain structure, a single Fe‐FinFET device realising 16 Boolean logic functions in two steps is reported. Furthermore, high speed (100 ns) and ultra‐low power (0.12 fJ) are also confirmed on the devices, indicating that the technology is promising for future logic‐in‐memory applications.

Ferroelectric memory is a promising candidate for next‐generation nonvolatile memory owing to its outstanding performance such as low power consumption, fast speed, and high endurance. However, the ferroelectricity of conventional ferroelectric materials will be eliminated by the depolarization field when the size drops to the nanometer scale. As a result, the miniaturization of ferroelectric devices was hindered, which makes ferroelectric memory unable to keep up with the development of integrated‐circuit (IC) miniaturization. Recently, a two‐dimensional (2D) In2Se3 was reported to maintain stable ferroelectricity at the ultrathin scale, which is expected to break through the bottleneck of miniaturization. Soon, devices based on 2D In2Se3, including the ferroelectric field‐effect transistor, ferroelectric channel transistor, synaptic ferroelectric semiconductor junction, and ferroelectric memristor were demonstrated. However, a comprehensive understanding of the structures and the ferroelectric‐switching mechanism of 2D In2Se3 is still lacking. Here, the atomic structures of different phases, the dynamic mechanism of ferroelectric switching, and the performance/functions of the latest devices of 2D In2Se3 are reviewed. Furthermore, the correlations among the structures, the properties, and the device performance are analyzed. Finally, several crucial problems or challenges and possible research directions are put forward. We hope that this review paper can provide timely knowledge and help for the research community to develop 2D In2Se3 based ferroelectric memory and computing technology for practical industrial applications. Two‐dimensional (2D) In2Se3 is a novel ferroelectric capable of fighting against the depolarization field at nanoscale. Thus, 2D In2Se3‐based low‐power consumption, high‐density ferroelectric devices are promising candidates for data storage applications. This review summarizes the major advances in 2D In2Se3, including structures, properties, phase/switching transitions, and device performance. Prospects for its future development and research directions are also presented.

Flexible Si-based Hf[sub.0.5] Zr[sub.0.5] O[sub.2] (HZO) ferroelectric devices exhibit numerous advantages in the internet of things (IoT) and edge computing due to their low-power operation, superior scalability, excellent CMOS compatibility, and light weight. However, limited by the brittleness of Si, defects are easily induced in ferroelectric thin films, leading to ferroelectricity degradation and a decrease in bending limit. Thus, a solution involving the addition of an ultra-thin Al buffer layer on the back of the device is proposed to enhance the bending limit and preserve ferroelectric performance. The device equipped with an Al buffer layer exhibits a 2Pr value of 29.5 μC/cm[sup.2] (25.1 μC/cm[sup.2] ) at an outward (inward) bending radius of 5 mm, and it experiences a decrease to 22.1 μC/cm[sup.2] (16.8 μC/cm[sup.2] ), even after 6000 bending cycles at a 12 mm outward (inward) radius. This outstanding performance can be attributed to the additional stress generated by the dense Al buffer layer, which is transmitted to the Si substrate and reduces the bending stress on the Si substrate. Notably, the diminished bending stress leads to a reduced crack growth in ferroelectric devices. This work will be beneficial for the development of flexible Si-based ferroelectric devices with high durability, fatigue resistance, and functional mobility.

In this study, a ferroelectric layer was formed on a ferroelectric device via plasma enhanced atomic layer deposition. The device used 50 nm thick TiN as upper and lower electrodes, and an Hf[sub.0.5] Zr[sub.0.5] O[sub.2] (HZO) ferroelectric material was applied to fabricate a metal–ferroelectric–metal-type capacitor. HZO ferroelectric devices were fabricated in accordance with three principles to improve their ferroelectric properties. First, the HZO nanolaminate thickness of the ferroelectric layers was varied. Second, heat treatment was performed at 450, 550, and 650 °C to investigate the changes in the ferroelectric characteristics as a function of the heat-treatment temperature. Finally, ferroelectric thin films were formed with or without seed layers. Electrical characteristics such as the I–E characteristics, P–E hysteresis, and fatigue endurance were analyzed using a semiconductor parameter analyzer. The crystallinity, component ratio, and thickness of the nanolaminates of the ferroelectric thin film were analyzed via X-ray diffraction, X-ray photoelectron spectroscopy, and transmission electron microscopy. The residual polarization of the (20,20)*3 device heat treated at 550 °C was 23.94 μC/cm[sup.2] , whereas that of the D(20,20)*3 device was 28.18 μC/cm[sup.2] , which improved the characteristics. In addition, in the fatigue endurance test, the wake-up effect was observed in specimens with bottom and dual seed layers, which exhibited excellent durability after 10[sup.8] cycles.

Ferroelectrics, known for their reversible spontaneous electric polarization, have garnered significant interest in both fundamental physics and applications, such as non-volatile memories and sensors. To address the scattered nature of contemporary ferroelectric research, we write this review which extensively outlines the developments and recent progress on the most studied ferroelectrics, including lead-based and lead-free ferroelectrics, low-dimensional HfO 2 -based ones, high-entropy relaxor ones, and multiferroics. The tuning methods for these ferroelectrics, including strain, doping, and constructing interfaces, are also systematically discussed. In addition, we also summarize the applications of ferroelectrics, including ferroelectric diodes and ferroelectric tunnel junctions, synaptic devices, domain-wall-based devices, and photoelectric devices, highlighting their significant potential for advanced electronic and optoelectronic devices. This review gives a comprehensive summary of ferroelectrics and offers insights into future research.

Understanding the suppression of ferroelectricity in perovskite thin films is a fundamental issue that has remained unresolved for decades. We report a synchrotron x-ray study of lead titanate as a function of temperature and film thickness for films as thin as a single unit cell. At room temperature, the ferroelectric phase is stable for thicknesses down to 3 unit cells (1.2 nanometers). Our results imply that no thickness limit is imposed on practical devices by an intrinsic ferroelectric size effect.

Spaldin and Fiebeg elaborate the major challenges for future research on magnetoelectric multiferroics. These include advances in fundamental theoretical concepts--such as integration of the concept of ferrotoroidicity, characterized by a spontaneous magnetization vortex, into the group of primary ferroics--that should lead to a more concise picture of the different forms of ferroic ordering and the relations between them.

Ferroelectric oxide materials have offered a tantalizing potential for applications since the discovery of ferroelectric perovskites more than 50 years ago. Their switchable electric polarization is ideal for use in devices for memory storage and integrated microelectronics, but progress has long been hampered by difficulties in materials processing. Recent breakthroughs in the synthesis of complex oxides have brought the field to an entirely new level, in which complex artificial oxide structures can be realized with an atomic-level precision comparable to that well known for semiconductor heterostructures. Not only can the necessary high-quality ferroelectric films now be grown for new device capabilities, but ferroelectrics can be combined with other functional oxides, such as high-temperature superconductors and magnetic oxides, to create multifunctional materials and devices. Moreover, the shrinking of the relevant lengths to the nanoscale produces new physical phenomena. Real-space characterization and manipulation of the structure and properties at atomic scales involves new kinds of local probes and a key role for first-principles theory.