Low Leakage Current Density Research Articles

Structural and dielectric investigation of thermal treated TiO2/ZrO2 composite thin films grown by chemical beam vapor deposition

TiO2/ZrO2 (TZ) composite binary oxides thin films were synthesized by Chemical Beam Vapor Deposition technique with a combinatorial approach, followed by annealed at 600 °C for 1 h. Three different element compositions were used in the composite films, with TiO2/ZrO2 ratio of ∼80/20, ∼70/30 and ∼60/40 at.%. X-ray diffraction analysis indicated that the Zirconium titanate crystalline phase was predominated in the TZ composite films, particularly those with higher concentration of ZrO2. The TZ film with ∼60/40 at.% exhibited a maximum dielectric constant of ∼35, a loss tangent of ∼3 and a low leakage current density of ∼1.7 × 10−9A/cm2. These results suggest that the synergistic combination of TiO2 and ZrO2 makes them a potential candidate for capacitor applications.

5.1 Å EOT and low leakage TiN/Al2O3/Hf0.5Zr0.5O2/Al2O3/TiN heterostructure for DRAM capacitor

Further scaling of dynamic random-access memory (DRAM) faces critical challenges because of the lack of materials with both high dielectric constant and low leakage. In this work, engineering Hf1−xZrxO2 (HZO) films to the morphotropic phase boundary (MPB) and inserting Al2O3 interface layers with a wide bandgap are utilized to overcome this bottleneck. By tuning Zr composition and the woken-up process, the ratio of tetragonal and orthorhombic phases is manipulated to achieve the desired high dielectric constant MPB state. On this basis, Al2O3 ultrathin layers are inserted to further enhance the dielectric constant as well as reduce the leakage current. As a result, a high dielectric constant of ∼ 46.7 (equivalent oxide thickness ∼ 5.1 Å) and low leakage current density (<10−7 A/cm2 at ±0.5 V) are achieved in TiN/Al2O3 (0.2 nm)/Hf0.5Zr0.5O2 (5.6 nm)/Al2O3 (0.3 nm)/TiN capacitors. Furthermore, long dielectric breakdown time of the heterostructure confirms its application potential. These results are useful for developing next generation DRAM capacitor devices.

Design and Fabrication of High-Efficiency, Low-Power, and Low-Leakage Si-Avalanche Photodiodes for Low-Light Sensing.

Since the advent of impact ionization and its application in avalanche photodiodes (APD), numerous application goals have contributed to steady improvements over several decades. The characteristic high operating voltages and the need for thick absorber layers (π-layers) in the Si-APDs pose complicated design and operational challenges in complementary metal oxide semiconductor integration of APDs. In this work, we have designed a sub-10 V operable Si-APD and epitaxially grown the stack on a semiconductor-on-insulator substrate with a submicron thin π-layer, and we fabricated the devices with integrated photon-trapping microholes (PTMH) to enhance photon absorption. The fabricated APDs show a substantially low prebreakdown leakage current density of ∼50 nA/mm2. The devices exhibit a consistent ∼8.0 V breakdown voltage with a multiplication gain of 296.2 under 850 nm illumination wavelength. We report a ∼5× increase in the EQE at 850 nm by introducing the PTMH into the device. The enhancement in the EQE is evenly distributed across the entire wavelength range (640-1100 nm). The EQE of the devices without PTMH (flat devices) undergo a notable oscillation caused by the resonance at specific wavelengths and show a strong dependency on the angle of incidence. This characteristic dependency is significantly circumvented by introducing the PTMH into the APD. The devices exhibit a significantly low off-state power consumption of 0.41 μW/mm2 and stand fairly well against the state-of-the-art literature. Such high efficiency, low leakage, low breakdown voltage, and extremely low-power Si-APD can be easily incorporated into the existing CMOS foundry line and enable on-chip, high-speed, and low-photon count detection on a large scale.

Evolution of High Dielectric Permittivity in Low-Temperature Solution Combustion-Processed Phase-Pure High Entropy Oxide (CoMnNiFeCr)O for Thin Film Transistors

An investigation of dielectric permittivity on the sintered high entropy oxide (HEO) capacitor composed of Co, Cr, Fe, Mn, and Ni (i.e., (CoCrFeMnNi)O) developed using solution combustion synthesis is performed. Stabilization of the phase in HEO is extremely important as it has a direct influence on the properties. In order to explore phase stabilization, in-depth studies of thermal, structural, morphological, and compositional analyses are carried out. The optimized processing parameters are further implemented on depositing (CoCrFeMnNi)O dielectric thin films followed by a thin film transistor. Irrespective of the reaction medium, the precursors undergo combustion at a low temperature below 250 °C, resulting in amorphous HEO. Upon crystallization at 500 °C, no secondary impurity oxides were detected and phase-stabilized to a spinel structure (Fd3m). A homogeneous distribution of all five cations without any segregation and a completely disordered occupancy of the cations were displayed by the bulk and thin films of HEOs. The spinel (CoCrFeMnNi)O exhibited high permittivity, with values approximately 7.3 × 102 (in bulk) and 3 × 101 (in a thin film), measured at 1 kHz owing to the entropy stabilization effect of HEO. Due to their high permittivity and low leakage current density (∼10–8 A/cm2), the (CoMnNiFeCr)O thin film was integrated into thin film transistors (TFTs) with molybdenum disulfide-channel. TFTs showed a field effect mobility of 8.8 cm2 V–1 s–1, an on–off ratio of approximately 105, a threshold voltage of −1.5 V, and a subthreshold swing of 0.38 V/dec. The low voltage operation (<5 V) of these TFTs makes solution combustion-derived HEO (CoMnNiFeCr)O a potential candidate in microelectronics and optoelectronics applications.

Multipurpose organic–inorganic hybrid dielectrics with photothermal crosslinking of zirconium-oxo clusters

Metal-oxo cluster molecules serve as effective building blocks in various applications, such as linkers for organic-inorganic hybrid materials, photoresists for extreme ultraviolet lithography, direct printing ink for micro/nanofabrication, and dielectrics for microelectronics. In this study, we investigate solution-based hexanuclear zirconium-oxo (Zr6-oxo) clusters and their thin-film fabrication process through efficient photothermal treatment to activate and polymerize the clusters. Various annealing conditions are analyzed by varying the temperature and deep ultraviolet light irradiation time. Under optimized conditions, the Zr6-oxo cluster thin-films are robust dielectrics with high breakdown strength and extremely low leakage current density (3.28 × 10−9 A/cm2 at 2 MV/cm). The excellent dielectric performance of Zr6-oxo cluster thin-films and direct patterning via a simple etching procedure make it a more accessible approach to developing micro/nanopatterned dielectric layers. The proposed method facilitates the use of Zr6-oxo clusters with simple processing rather than complex multiprocessing. In addition, the observations suggest that other metal-oxo cluster thin-film systems can be investigated using similar approaches.

Ferroelectric and piezoelectric properties of lead-free Li0.06(K0.5Na0.5)0.94NbO3 thin films

Lead-free ([Formula: see text][Formula: see text])NbO3 (KNN) and [Formula: see text]([Formula: see text][Formula: see text])[Formula: see text]NbO3 (LKNN) thin films were fabricated by a sol-gel method. The effects of Li substitution on crystal structure, microstructure and electrical properties of KNN film were systematically studied. Li doping can enhance the ferroelectric and piezoelectric properties of KNN film. Compared with pure KNN film, the LKNN film possesses larger remanent polarization ([Formula: see text] [Formula: see text] 9.3 [Formula: see text]C/[Formula: see text]) and saturated polarization ([Formula: see text] [Formula: see text] 41.2 [Formula: see text]C/[Formula: see text]) and lower leakage current density ([Formula: see text]A/[Formula: see text] at 200 kV/cm). Meanwhile, a typical butterfly shaped piezoelectric response curve is obtained in the LKNN film with a high piezoelectric coefficient ([Formula: see text] [Formula: see text] 105 pm/V). Excellent fatigue resistance ([Formula: see text][Formula: see text] switching cycles) and aging resistance ([Formula: see text] 180 days) demonstrate the long-term working stability of LKNN film. These findings indicate that KNN-based lead-free piezoelectric films have a broad application prospect in microelectromechanical systems (MEMS).

Low Leakage in High‐k Perovskite Gate Oxide SrHfO3

AbstractReducing the leakage current through the gate oxide is becoming increasingly important for power consumption reduction as well as reliability in integrated circuits as the semiconducting devices continue to scale down. Here, this work reports on the high‐k dielectric SrHfO3(SHO) based devices with ultralow leakage current density via pulsed laser deposition (PLD). The ultralow current density is achieved by optimizing the growth conditions and the associated structural properties. In the optimized conditions, the dielectric properties of the 50‐nm‐thick SHO capacitors are measured: high dielectric constant (κ = 32), low leakage current density (&lt;10−8A cm−2at 2 MV cm−1), and large breakdown field (EBD &gt; 4 MV cm−1). The surprisingly low leakage current density of SHO is ascribed to the large bandgap (≈6 eV), the large conduction band offset (CB offset &gt; 3 eV) with respect to the semiconductor, and the low density of defect states inside the bandgap. The optimized SHO dielectric with high dielectric constant and ultralow leakage current density is proposed for future low‐power consumption devices based on Si as well as perovskite oxide semiconductors.

Low-temperature processable and photo-crosslinkable polyimide gate dielectric for flexible thin-film transistor

A fully soluble and photo-crosslinkable gate dielectric (6 F-SPI-Cinnamoyl: 6 F-SPI-CM) was synthesized. First, hydroxyl group substituted polyimide (6 F-SPI-Hydroxyl: 6 F-SPI-OH) polymer was prepared using monomers, 5-(2,5-dioxytetrahydrofuryl)-3-methyl-3-cyclohexene-1,2-dicarboxylic anhydride (DOCDA) and 4,4’-(perfluoropropane-2,2-diyl)dianiline (6FHAB) through polycondensation reaction. And, then 6 F-SPI-OH was further reacted with cinnamoyl chloride to prepare a photo-crosslinkable 6 F-SPI-CM. The thin film of photo-crosslinked 6 F-SPI-CM (C-6F-SPI-CM) showed the extremely low leakage current density of <1.0 x10−11 A/cm2. In addition, 6 F-SPI-CM was easily patterned by selective UV-light exposure. A flexible pentacene thin-film transistor (TFT) on polyethersulfone (PES) substrate with photo-crosslinked 6 F-SPI-CM as a gate dielectric showed a field effect mobility of 0.11 cm2/Vs with no hysteresis behavior.

Effect of Heat Treatment on Zirconium Oxide High‐k Gate Dielectric in Silicon‐Based Metal Oxide Semiconductor Capacitors

Herein, zirconia thin films are successfully prepared on silicon substrates using the sol–gel method, and the microstructure, optical, and electrical properties of zirconia high‐k gate dielectric films are analyzed at different annealing temperatures. X‐ray diffraction results show that ZrO2 films crystallize above 500 °C and the grain size increases with the increase of annealing temperature; X‐ray photoelectron spectroscopy analysis confirms that metal–oxygen bonds can be effectively formed and defects in the films are eliminated by annealing treatment, with significant changes in the valence band shift (ΔEv) and conduction band shift (ΔEc) with increasing annealing temperature. Analysis of the optical properties of the films by UV‐Vis confirms that all zirconia films have high transmittance, with the bandgap increasing from 5.54 to 5.74 eV with increasing annealing temperature. Atomic force microscope and field emission scanning electron microscope show that the film quality is better and the root mean square roughness of the zirconia films increases from 0.551 to 1.190 nm and the film thickness decreases from 176.19 to 58.73 nm with increasing annealing temperature. Electrical performance tests show that proper annealing is effective in improving electrical properties, such as obtaining a larger dielectric constant (k) and a lower leakage current density.

Observation of MOSFET-like behavior of a TFT based on amorphous oxide semiconductor channel layer with suitable integration of atomic layered deposited high-k gate dielectrics

A series of different high κ dielectrics such as HfO2, ZrO2, and Al2O3 thin films were studied as an alternative material for the possible replacement of traditional SiO2. These large areas, as well as conformal dielectrics thin films, were grown by the atomic layer deposition technique on a p-type silicon substrate at two different deposition temperatures (150 and 250 °C). Atomic force microscopic study reveals that the surface of the films is very smooth with a measured rms surface roughness value of less than 0.4 nm in some films. After the deposition of the high κ layer, a top metal electrode was deposited onto it to fabricate metal oxide semiconductor capacitor (MOSCAP) structures. The I–V curve reveals that the sample growth at high temperatures exhibits a high resistance value and lower leakage current densities. Frequency-dependent (100 kHz to 1 MHz) C–V characteristics of the MOSCAPs were studied steadily. Furthermore, we have prepared a metal oxide semiconductor field-effect transistor device with Al-doped ZnO as a channel material, and the electrical characteristic of the device was studied. The effect of growth temperature on the structure, surface morphology, crystallinity, capacitance, and dielectric properties of the high κ dielectrics was thoroughly analyzed through several measurement techniques, such as XRD, atomic force microscopy, semiconductor parameter analysis, and ultraviolet-visible spectroscopy.

Optimizing Photonic Annealing Technique for High-k Dielectric of Full-Solution-Processed Oxide Thin Film Transistor

In this article, it is demonstrated that the photonic annealing process of ultraviolet (UV) irradiation or rapid thermal annealing (RTA)-assisted LA technique can effectively enhance the bias and illumination stability of full-solution-processed oxide thin film transistor (TFT). Although both post-annealing treatments have comparable effects, UV irradiation has relatively less heat loss and time consumption of only 3 min, compared to the RTA process that heats at a temperature of 400 °C and holds 10 min. Depending on the laser annealing (LA)/UV technique, the amorphous hafnium-aluminum oxide (HAO) dielectric thin film exhibits a smooth surface with an rms value of 0.293 nm, a high optical bandgap of 6.19 eV, and good dielectric performance with high dielectric constants of 12.9, low leakage current densities, and high breakdown field of about 4 MV/cm. Moreover, full-solution-processed indium-tin-oxide (ITO)–HAO–tungsten-zinc-tin-oxide (WZTO) TFT shows excellent overall properties with the mobility ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu $ </tex-math></inline-formula> ) of 10.65 cm <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{{2}}\cdot \text{V}^{-{1}}\cdot \text{s}^{-{1}}$ </tex-math></inline-formula> , subthreshold swing (SS) of 198 mV/dec. And the device has good bias and illumination stability, especially the threshold voltage ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${V}_{T}$ </tex-math></inline-formula> ) shifts are all less than 3 V under positive bias illumination stress (PBIS) and negative bias illumination stress (NBIS) testing for 10000 s. These indicate the potential for the photonic annealing process of the UV-assisted LA technique on improving the stability of the full-solution-processed TFTs, which is attributed to high-throughput fabrication for large-area, transparent, and flexible electronics.

Effect of ‘Mo’ doping into BiMnO3 on structural, dielectric, and leakage current properties

The simultaneous existence of more than one ferroicorder (ferroelectric, magnetic and ferroelastic) i.e., multiferroism in materials is the center of attention of the current materials researchers. Multiferroism is rare in the materials due to the different chemistry of the ferroic orders and highly useful in various device applications such as in spintronics. In this connection, BiMnO3 is one of the multiferroic materials among the number of available multiferroic materials. It shows ferroelectricity as well as antiferromagnetic nature simultaneously . In the present work, efforts have been made to synthesize the BiMnO3 in pure phase as well as with the doping of ‘Mo’ in the ratio of 2 %, 4 %, and 8 % via solid-state reaction route and denoted by BMM0, BMM2, BMM4, and BMM8, respectively. The structural analysis confirms the monoclinic structure along with some impurities and also confirms the polycrystalline nature of all the samples. Impurities reduce with the ‘Mo’ doping into BiMnO3. The dielectric and leakage current density measurements confirm the high dielectric constant, low dielectric loss, and low leakage current density values in the samples as increment in the ‘Mo’ content into the pure BiMnO3 phase. The BMM8 has the dielectric constant (∼2265 at 1 kHz and ∼ 385 at 10 kHz), dielectric loss (∼2.32 at 1 kHz and ∼ 2.66 at 10 kHz), and leakage current density (∼3.73 × 10-4 A/cm2 at 2 V and ∼ 1.00 × 10-3 A/cm2 at 3 V).

SiO2: A Novel Electrolyte for High-Performance All-Solid-State Electrochromic Devices

For the practical application of electrochromic devices (ECDs), the development and preparation of high-performance electrolyte materials is one of the urgent problems to be solved. In this work, an all-solid-state ECD with the integrated structure of glass/ITO/WO3/Li/SiO2/NiO/ITO has been prepared by the magnetron sputtering method. The amorphous SiO2 film prepared by pulsed direct current reactive magnetron sputtering was used as the electrolyte layer in the ECD for the first time and shows promising potential due to its ultrahigh transparency, good intrinsic electronic insulation, and loose structure for fast ion conduction. The ECD exhibits low leakage current density (8.5 μA cm–2 for bleaching and 43.4 μA cm–2 for coloring), high optical modulation (ΔT = 71.9% at 707 nm), fast response speed (1.1 s for the bleaching process and 8.5 s for the coloring process), excellent cycle stability, and high coloration efficiency (126.4 cm2 C–1). This work not only indicates that SiO2 as a dielectric material can be used as the electrolyte layer in all-solid-state ECDs but also provides new avenues in the selection of electrolyte materials for the preparation of high-performance ECDs.

Process temperature-dependent interface quality and Maxwell-Wagner interfacial polarization in atomic layer deposited Al2O3/TiO2 nanolaminates for energy storage applications.

Considering the excellent tunability of electrical and dielectric properties in binary metal oxide based multi-layered nanolaminate structures, a thermal atomic layer deposition system is carefully optimized for the synthesis of device grade Al2O3/TiO2 nanolaminates with well-defined artificial periodicity and distinct interfaces, and the role of process temperature in the structural, interfacial, dielectric and electrical properties is systematically investigated. A marginal increase in interfacial interdiffusion in these nanolaminates, at elevated temperatures, is validated using X-ray reflectivity and secondary ion mass spectrometry studies. With an increase in deposition temperature from 150 to 300 °C, the impedance spectroscopy measurements of these nanolaminates exhibited a monotonic increment in dielectric constant from ∼95 to 186, and a decrement in dielectric loss from ∼0.48 to 0.21, while the current-voltage measurements revealed a subsequent reduction in leakage current density from ∼2.24 × 10-5 to 3.45 × 10-7 A cm-2 at 1 V applied bias and an improvement in nanobattery polarization voltage from 100 mV to 700 mV, respectively. This improvement in dielectric and electrical properties at elevated processing temperature is attributed to the reduction in impurity content along with the significant enhancement in sublayer densities and the conductivity contrast driven Maxwell-Wagner interfacial polarisation. Additionally, the devices fabricated at 300 °C exhibited a higher capacitance density of ∼22.87 fF μm-2, a low equivalent oxide thickness of ∼1.51 nm, and a low leakage current density of ∼10-7 A cm-2 (at 1 V bias), making this nanolaminate a promising material for high-density energy storage applications. These findings highlight the ALD process temperature assisted growth chemistry of Al2O3/TiO2 nanolaminates for superior dielectric performance and multifaceted applications.

Self-Assembled Au/P3HT, High-k Bilayer Dielectric-Based Solution Processed Low Voltage OTFT for Multiparametric Ammonia Sensor at Room Temperature

A self-assembled, fully solution-processed, bilayer (TiO2/HfO2) dielectric-based thin film transistor (TFT) has been fabricated and explored for highly sensitive ammonia gas at room temperature (RT—25 °C). The bilayer dielectric film has been grown over a heavily boron-doped silicon substrate (p++ Si), and the thickness of each layer has been optimized by spin coating rotation speed and spin time to find a high-quality gate oxide. The obtained dielectric has a high areal capacitance of 0.926 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{F}$ </tex-math></inline-formula> /cm2, low rms roughness of 0.914 nm, and low leakage current density of ~1 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{A}$ </tex-math></inline-formula> /cm2, high dielectric constant of ~42, which are much more favorable for the high-performance organic TFT (OTFT). The incorporation of the TiO2 layer in between the p++ Si and HfO2 layer enhances the areal capacitance and minimizes the rms roughness (TiO2 minimizes the no. of interface trap states at the dielectric/semiconductor interface) of the bilayer dielectric film, thereby improving the charge transfer mechanism. The developed high- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${k}$ </tex-math></inline-formula> bilayer solution-processed dielectric layer has been utilized to develop a low voltage operated (−1.5 V) OTFT for ammonia (NH3) gas at RT. The fabricated OTFT device utilized the solution-processed floating film transfer method (FTM) to grow the Au(gold) doped P3HT film as a sensing/organic semiconductor channel (OSC) layer. The Au/P3HT sensing layer shows a quick response/recovery time (5/17 s), with a high sensing response of 55% (5 ppm) toward the NH3 analyte. The study aims to find a low-voltage, solution-processed, cost-efficient OTFT device for a high-performance gas sensor at RT.

A novel hierarchical porous activated carbon-organic composite cathode material for high performance aqueous zinc-ion hybrid supercapacitors

Zinc-ion hybrid supercapacitors (ZIHSCs) are among the most promising electrochemical energy storage technologies because of their high energy density, environmental sustainability, low price, and inherent security. Hence, we have developed a novel energy storage system that uses a hierarchical porous activated carbon with redox-active organic materials as an active hybrid cathode material for ZIHSCs. The large surface area of chitosan-derived activated carbon (Ch-C), the fast electron transfer mechanism of bis-glycinyl naphthalene diimide (H2BNDI), and zinc's bivalent nature all together contribute to the high energy density of redox-active zinc-ion hybrid supercapacitors (RAZIHSCs). The fabricated device exhibited an outstanding energy output of 250 Wh kg−1 @ 0.1 A g−1 and a power output of 9.5 kW kg−1 @ 10 A g−1 due to the additional pseudocapacitive behaviour arising out of the redox-active H2BNDI material. Additionally, 100% coulombic efficiency and 80% capacitance retention are still attained after 10000 cycles at a high current density of 5 A g−1. As a result of the complex chemical reactions between Zn2+-ions and H2BNDI moiety in the composite cathode, the proposed RAZIHSCs demonstrated a lower self-discharge rate (23% in 25 h) with extremely low leakage current density (15 mA g−1).

Microstructure, charge carrier conduction mechanism model, dielectric properties and leakage current analysis of Dy2FeMnO6 nanomaterial

The structure, microstructure, charge transport properties, dielectric properties, and leakage current density of Dy2FeMnO6 synthesized by the auto combustion method are investigated in this study. The monoclinic crystal structure of the sample with space group P21/n was observed. The CoO6 and MnO6 octahedra were found distorted and tilted. The calculation of the bond valence sum confirmed the +3 and + 3/+4 oxidation states of Fe and Mn, respectively. The average crystallite, particle, and grain sizes were 43.01, 94, and 187.68 nm, respectively. The anticipated stoichiometry of the constituent elements was confirmed by energy–dispersive X–ray spectra. The frequency–dependent conductivity obeyed Jonscher’s power law, and the frequency exponent associated with this law increased with temperature, indicating the non–overlapping small polaron tunnelling (NSPT) mechanism for charge conduction. The enhancement of the dielectric loss tangent with temperature was consistent with the dc conductivity. The frequency dependence of dielectric properties was explained using Havriliak–Negami formalism. The sample followed Vogel–Fulcher law, which is similar to the relaxor ferroelectrics, and the ferroelectricity increased with frequency. Conduction, migration, and dielectric relaxation all have similar activation energies. The sample exhibited low leakage current density, which followed Schottky emission with a barrier height of 0.02(4) eV. The obtained results were compared with other rare–earth–based double perovskites.

Enhancement of breakdown strength in relaxor ferroelectric Ba(Zr0.3Ti0.7)O3 thin film via manipulating growth oxygen pressure

Improving the energy storage performance of dielectric capacitors has always been a spotlight. Large polarization and high breakdown strength are two key parameters for achieving excellent energy storage performance. Herein, in Ba(Zr0.3Ti0.7)O3 (BZT) thin films an ultrahigh breakdown strength of 7.94 MV/cm is achieved due to the low leakage current density by regulating the growth oxygen pressure at a low level of 5 Pa. A combination of remarkable recoverable energy storage density (Wrec) of 89.9 J/cm3 and high efficiency (η) of 71.6% is successfully realized. Furthermore, the energy storage and insulation properties display superb fatigue endurance up to 107 cycles, indicating that the BZT film-based dielectric capacitors are quite competitive in the field of electronic power.

Significantly enhanced hybrid improper ferroelectricity of Ca3Ti2O7 ceramics by the oxygen vacancy engineering

Ca3Ti2O7 materials with hybrid improper ferroelectricity call tremendous interest due to their great potential in designing novel room-temperature single-phase multiferroics with a strong magnetoelectric coupling effect. However, achieving Ca3Ti2O7-based ceramics with superior room-temperature ferroelectricity remains a crucial challenge. Herein, Ca3Ti2O7 ceramics were prepared by a tartaric acid sol–gel method and sintered in air and oxygen atmospheres, respectively. It was found that the long-time high-temperature sintering in air could lead to the formation of CaTiO3/Ca3Ti2O7/CaTiO3 sandwich structure, and oxygen-enriched sintering could effectively avoid the formation of CaTiO3 phase on the surface. The superior hybrid improper ferroelectricity is attained in Ca3Ti2O7 ceramics sintered in oxygen atmosphere with a higher remnant polarization (3.63 μC/cm2) and lower coercive electric field (72.6 kV/cm) obtained by positive-up and negative-down method, which is better than the ceramic sample sintered in air. The significantly better ferroelectricity is benefited from the synergistic effects of its larger distortion of oxygen octahedron, larger grain size, and lower oxygen vacancy concentration. Due to its low leakage current density, Ca3Ti2O7 ceramics sintered in oxygen atmosphere exhibit the remanent polarization as high as 7.40 μC/cm2 under the conditions of 1 Hz and 200 kV/cm obtained by dynamic hysteresis measurement mode. Furthermore, there are obvious stripe ferroelectric domains, which provide direct evidence for the excellent hybrid improper ferroelectricity of Ca3Ti2O7 ceramics. These findings demonstrate that the oxygen vacancy engineering is an effective strategy to improve hybrid improper ferroelectricity of Ca3Ti2O7 materials.

Impact of Ferroelectric Layer Thickness on Reliability of Back‐End‐of‐Line‐Compatible Hafnium Zirconium Oxide Films

Due to its ferroelectricity, hafnium oxide has attracted a lot of attention for ferroelectric memory devices. Amongst different dopant elements, zirconium is found to be beneficial due to the relatively low crystallization temperature of hafnium‐zirconium‐oxide (HZO), thus it is back‐end‐of‐line (BEoL) compatible. The thickness of HZO has a significant impact on ferroelectric device reliability. High operation temperatures and high endurance are important criteria depending on the application. Herein, various HZO thicknesses (7, 8, and 10 nm) in MFM (metal‐ferroelectric‐metal) capacitors are investigated at varying operation temperatures (25 to 175 °C) at varying electric fields (±3 to ±5.4 MV cm−1) with respect to polarization, leakage current, endurance, and retention. 7 nm HZO showed promising results with an endurance of 107 cycles, with a low leakage current density, and almost no retention loss after 10 years. Extrapolated results at operation conditions (±2 MV cm−1 and 10 MHz) showed an endurance of 1010 cycles.