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High-performance dielectric capacitor represents an emerging technological goal for energy storage in modern electrical and electronic systems. In this work, we report a lead-free film capacitor based on the Bi(Mg1/2Ti1/2)O3 modified BiFeO3-Sr0.7Bi0.2TiO3 relaxor. A large recoverable energy storage density of 77.5 J/cm3, together with an efficiency of 56.1% is achieved in the film with 15 mol. % Bi(Mg1/2Ti1/2)O3 in composition. The film also exhibits excellent fatigue endurance with a reduction less than 3% over 1 × 108 cycles in both recoverable energy storage density and efficiency. Such good properties are ascribed to the improved electrical insulation and breakdown strength and the enhanced relaxor behavior by introducing the bismuth-based perovskite-like compound.

Polymer dielectrics with a high energy density, an outstanding breakdown strength, and a low dielectric loss are currently in great demand in the field of film capacitors. Here, on the basis of fundamental understanding of dielectric relaxation in cellulose, environmentally friendly regenerated cellulose-based dielectrics were fabricated by manipulating their intrinsic hydrogen bonding network, in which hydroxyl groups of cellulose were reacted with epichlorohydrin (ECH) to simultaneously reduce the density of the intra- and intermolecular hydrogen bonding networks and the crystallinity for activating the movement of polar groups. As a result, when the molar ratio of ECH to glucose units of cellulose is 1:1, the regenerated cellulose-based dielectrics exhibited the highest dielectric constant of 9.7 at 103 Hz with the dielectric loss in an order of 10−2 and an energy density of 2.16 J/cm3 with a high charge–discharge efficiency of >85% at 200 MV/m. This methodology presented here provides a promising avenue for designing and improving the dielectric properties of cellulose-based dielectrics.

Polymer-based dielectrics are widely applied in the fields of electronics and electrical power systems due to the high breakdown strength, excellent flexibility, and unique self-healing capability. However, the low stored energy density and unsatisfactory heat management of polymer dielectrics hinder the development of polymer-based film capacitors. In this research, artificial composites with improved capacitive energy storage and thermal conductivity are fabricated by blending the two-dimensional semiconductive MXene sheets with a polyimide (PI) matrix. Remarkably, a PI based composite with 1 wt. % MXene sheets increases its dielectric permittivity from ≈3.27 to ≈3.53 and enhances its discharged energy density from ≈1.93 to ≈2.38 J/cm3 while maintaining its low dielectric loss of 80%. Meanwhile, a high in-plane thermal conductivity of 0.418 W m−1 K−1 is achieved for PI/MXene composites with 5 wt. % MXene. In addition, the distribution of temperature field inside the composites has been investigated by a finite element method. These results represent a strategy in polymer dielectrics to achieve simultaneous high energy density and thermal conductivity, which may also have potential for applications in high temperature environments.

Dielectric capacitors deliver the highest power density and operating voltage among known energy storage devices that are integrable in modern electronic and electrical systems. Ferroelectric polymers are promising dielectric energy storage media for film capacitors due to their superiority in excellent dielectric properties, high breakdown strength, and flexibility. Polymer-based nanocomposites by incorporating high-dielectric-constant nanofillers into the ferroelectric polymer matrix exhibit great potential for superior energy storage performances. This Perspective focuses on the development and progress of high-energy-density ferroelectric polymers and their nanocomposites. First, approaches are proposed to tune the ferroelectric hysteresis for suppressed dielectric and energy losses in ferroelectric polymers, which is the premise to achieve high energy density and high efficiency. Second, the energy storage properties of ferroelectric nanocomposites greatly depend on multiple factors such as nanofiller features, polymer/filler interfaces, and spatial composite structures, and effective strategies enabling enhancements of the dielectric constant and breakdown strength in nanocomposites are discussed. In the last part, some existing challenges and future perspectives are proposed to develop high-energy-density ferroelectric polymer-based materials for energy storage applications.

As one of the key components of an electromagnetic pulse simulator, the peaking capacitor is coaxially constructed with a laminate structure utilizing alternative thin metal rings and polymer film dielectrics, which is designed as a part of the antenna. This paper presents a coaxial film capacitor with a novel structure to improve its flashover performance. First, the relationship between the capacitance and the capacitor’s structural parameters are deduced, and a theoretical basis of lengthening the polymer film dielectrics to enhance the flashover performance is discussed. Based on the theoretical analysis, two 150 pF, 3-layer coaxial film capacitors with different extended lengths for the polymer film dielectrics (10 and 60 mm) are designed and developed. For the capacitor with a 60 mm extended film dielectric, the polymethylmethacrylate rings are adhered to the thin metal rings to support the polymer film dielectrics using a soft adhesive. Electric field analyses show that a longer extended length could decrease the surface field at the edge of the polymer film dielectric by as much as 93%. Comparative insulation experiments show that the flashover voltage for the improved capacitor is 89.9% higher than the original one. The influence of the capacitor’s polymer extensions (including the polymer supporting rings and the film dielectrics) on the radiating field of a cone antenna is analyzed numerically, and the results show that only slight changes are introduced into the radiating field. Finally, a designed 350 pF, 20-layer coaxial film capacitor with lengthened film dielectrics is presented.As one of the key components of an electromagnetic pulse simulator, the peaking capacitor is coaxially constructed with a laminate structure utilizing alternative thin metal rings and polymer film dielectrics, which is designed as a part of the antenna. This paper presents a coaxial film capacitor with a novel structure to improve its flashover performance. First, the relationship between the capacitance and the capacitor’s structural parameters are deduced, and a theoretical basis of lengthening the polymer film dielectrics to enhance the flashover performance is discussed. Based on the theoretical analysis, two 150 pF, 3-layer coaxial film capacitors with different extended lengths for the polymer film dielectrics (10 and 60 mm) are designed and developed. For the capacitor with a 60 mm extended film dielectric, the polymethylmethacrylate rings are adhered to the thin metal rings to support the polymer film dielectrics using a soft adhesive. Electric field analyses show that a longer extended length cou...

Dielectric thin film capacitors, storing large charge density, are useful in electric energy storing devices. Highly oriented lead-free BaZr0.20Ti0.80O3 (BZT20) thin films were grown on a conducting bottom layer La0.7Sr0.3MnO3 deposited on a MgO (100) substrate under an oxygen atmosphere using a pulsed laser deposition technique. X-ray diffraction studies indicate that BZT20 films were stabilized in a (100) oriented tetragonal phase. Microstructural studies on thin films indicate a smooth film (a roughness of ∼1.25 nm) with a thickness of around 320 nm. The structural sensitive A1(TO2) Raman band exhibits a discontinuous change across the tetragonal-cubic phase transition temperature Tc ∼ 275 K. The appearance of the broad Raman band in the cubic (Pm−3m) phase at an elevated temperature suggests the activation of symmetry forbidden Raman active bands. The temperature dependent band frequency and integrated intensity of the structural sensitive A1(TO2) band show anomaly across Tc. Temperature dependent dielectric studies (100–650 K) carried out in a wide range of frequencies 102–106 Hz on a fabricated Pt/BZT20/LSMO metal-insulator-metal capacitor suggest a broad dispersive peak of around 290 K. The polarization relaxation follows the Vogel-Fulcher relation with an activation energy of Ea = 0.047 eV and a freezing temperature of Tf = 246 K. The slim polarization P-E loops with a remanent polarization of ∼89.6 μC/cm2 and an EC value of ∼0.29 MV/cm were observed, suggesting its local ferroelectric ordering in corroboration with Raman and dielectric findings. From the P-E loop analysis, a large energy storage density of 31.9 J/cm3 and an energy storage efficiency of 56% were obtained. Our experimental results revealed that the BZT20 thin film capacitors have potential for energy storage device applications.

Polyvinylidene fluoride (PVDF) based fluoropolymers are promising materials for capacitors in pulsed power applications because of their high dielectric constant compared to other polymers. High energy losses, such as conduction losses or ferroelectric losses, impose great challenges for large-scale commercialization. Here, we present a systematic study on the high field electrical conduction of biaxially oriented PVDF films. The conductivity shows a surprising initial decrease, followed by a gradual increase, with increasing electric field. The unexpected decrease in conductivity arises from ferroelectric switching, and the electric field of the transition point in conductivity is consistent with the switching field for polarization reversal. This suggests that PVDF films with pre-aligned ferroelectric domains could simultaneously exhibit reduced high field conduction losses and ferroelectric losses.

Developing lead-free film dielectric capacitors with high-performance of energy storage density, efficiency, fatigue endurance, and thermal stabilities is desirable. Here, we report energy storage properties in (1-x)BaTiO3-xBi3.25La0.75Ti3O12 thin films. It is revealed that a 0.6BaTiO3-0.4Bi3.25La0.75Ti3O12 thin film with a thickness of 280 nm and a crystallization temperature of 650 °C shows a breakdown strength of 3.23 MV/cm with a large polarization value and dielectric constant. An ultrahigh energy storage density of 61.1 J/cm3 and an efficiency of 84.2% are simultaneously achieved at room temperature. Additionally, excellent fatigue endurance after 6 × 109 cycles and good thermal stability up to 150 °C are observed, implying excellent energy storage performance in 0.6BaTiO3-0.4Bi3.25La0.75Ti3O12 thin films.

Flexible dielectric polymer films with high energy storage density and high charge-discharge efficiency have been considered as promising materials for electrical power applications. Here, we design hierarchical structured nanocomposite films using nonlinear polymer poly(vinylidene fluoride-HFP) [P(VDF-HFP)] with inorganic h-boron nitride (h-BN) nanosheets by electrospinning and hot-pressing methods. Our results show that the addition of h-BN nanosheets and the design of the hierarchical multilayer structure in the nanocomposites can remarkably enhance the charge-discharge efficiency and energy density. A high charge-discharge efficiency of 78% and an energy density of 21 J/cm3 can be realized in the 12-layered PVDF/h-BN nanocomposite films. Phase-field simulation results reveal that the spatial distribution of the electric field in these hierarchical structured films affects the charge-discharge efficiency and energy density. This work provides a feasible route, i.e., structure modulation, to improve the...

We evaluate different switching behaviors of lead zirconate titanate (PZT) thin film capacitors with two different geometries: one, a square 100×100 μm; the second, a ribbon (1.6 μm width but with approximately the same total area), as a function of temperature T, and applied electric field E. The ribbon capacitor shows a stronger dependence (by ca. 70%) of activation field on T and E. This is interpreted as a chemical reduction of edge material in the long-perimeter ribbons due to plasma etching. In order to understand and model the different domain switching of these two types of PZT capacitor, we also investigate impedance spectra at various temperatures from 27 to 470 °C. From ac conductance spectra, both square- and ribbon-type capacitors have similar trap levels, 0.38±0.02 eV. From analysis of conductivity spectra, we find that the ribbon capacitor contains an additional 0.19±0.02 eV trap level attributed to H–O dipoles due to hydrogen reduction; the latter trap results in domain pinning, which is i...

Self-clearing metallized film capacitor technology offers the highest energy density among high voltage capacitor technologies. The primary limitation of this technology under pulse discharge conditions is failure of the plasma sprayed end connections. Transient nonlinear finite element analysis with coupled electric and thermal fields is applied to quantify the temperature rise around a contact spot along the end connection as a function of discharge current, contact spot size, time and distance between contact spots along the contact edge. An analytic approximation is developed to compute these parameters which agrees to within a few percent with the finite element analysis.

We have performed Sawyer–Tower hysteresis measurements on micron sized Pb(Zr,Ti)O3 (PZT) capacitors prepared on Pt/Ti/SiO2/Si substrates and patterned with a focused ion beam. Owing to a numerical compensating technique, we show that the increase of both linear dielectric constant er and maximum polarization Pmax, when decreasing the size of the capacitors, is artificial and mainly due to the parasitic effect of the probing setup. Moreover, a suitable method is proposed to accurately determine and correct for the additional parasitic capacitance in parallel with the standard capacitor. Under these conditions, the dielectric and ferroelectric properties of micron sized PZT capacitors are found to be quite similar to those measured on a large contact, i.e., the device properties are area independent.

Fatigue-free and highly c-axis oriented Bi4−xPrxTi3O12 (BPrT, x=0.85) thin films were grown on Pt/TiO2/SiO2/Si (100) substrates using the method of metalorganic sol decomposition. The BPrT film capacitor with a top Pt electrode showed significantly improved values of the remanent polarization (Pr) and the nonvolatile charge as compared to those of the Bi4−xLaxTi3O12 (x=0.75) film capacitor, recently known as a promising candidate for nonvolatile memories. The 2Pr value of the BPrT capacitor was 40 μC/cm2 at an applied voltage of 10 V while the net nonvolatile charge was as high as 20 μC/cm2 and remained essentially constant up to 4.5×1010 read/write switching cycles at a frequency of 1 MHz. In addition to these, the capacitor showed excellent charge-retention characteristics with its sensing margin of 16 μC/cm2 and a strong resistance against the imprinting failure.

Thickness dependence of leakage current behavior in Pt/(Ba,Sr)TiO3/Pt film capacitors was investigated by fabricating epitaxial (Ba,Sr)TiO3 thin films having different thicknesses of 55–225 nm but with an identical interface state on Pt(001)/MgO(001) substrates by a radio-frequency magnetron sputtering technique. In the 55-nm-thick film, the Schottky emission is found to be a main leakage mechanism over a wide electric field range. In sharp contrast, instead of the Schottky emission, the Fowler–Nordheim tunneling dominates particularly in the thicker films (⩾90 nm) at high electric fields. According to the energy band model proposed to explain these results, the major leakage conduction mechanism is likely to be associated with overlapping of the depletion layers formed at the top and bottom interfaces.

Environmentally benign Bi3.25La0.75Ti3O12 (BLTO) thin film capacitors were prepared by a cost effective chemical solution deposition method for high energy density storage device applications. Low annealing temperature annealed BLTO thin films showed very slim hysteresis loops with high maximum and small remnant polarization values. Increasing the applied electric field to 2040 kV/cm, the optimized BLTO thin films show a high recoverable energy density of 44.7 J/cm3 and an energy efficiency of 78.4% at room temperature. Additionally, the BLTO thin film capacitors exhibited excellent fatigue endurance after 4 × 108 cycles and a good thermal stability up to 140 °C, proving their strong potential for high energy density storage and conversion applications.

Surface breakdown discharges are one probable failure mechanism of metallized polymeric film capacitors used in power systems, traction drives, and other technological applications. To assess whether surface breakdown discharges may undergo considerable elongation on the electrode surface to affect significantly capacitor performance, an equivalent electric circuit model is developed for metallized polymer film capacitors under the thermal equilibrium condition. With the aid of a surface field gradient mechanism, propagation of surface plasmas is studied and the necessary condition for their possible elongation is obtained. Numerical examples of a metallized film capacitor are used to demonstrate that surface breakdown plasmas and their elongation are unlikely to affect capacitor performance in a significant fashion. Then the generic problem of plasma propagation is restudied under thermally nonequilibrium conditions. Based on a heat conduction formulation in the one-dimensional limit, a temperature gradient mechanism is proposed to explain the possible elongation of breakdown plasmas on an electrode surface. Numerical examples are again used to deduce that thermally nonequilibrium surface plasmas are unlikely to evolve into catastrophic flashover arcs to fail film capacitors.

The nonlinear response of ferroelectric BaxSr1−xTiO3 films to microwave electric field intensity up to ∼3×106 V/m was studied. Two techniques were used for this investigation: (i) 10 GHz pulsed power measurements, and (ii) 4 GHz intermodulation distortion (IMD) measurements. The nonlinear distortion of the resonant curve under microwave pulsed power and generation of the third-order IMD products in microwave resonators using ferroelectric film planar capacitors were measured. The use of microwave pulses and continuous signals enabled the separation of the nonlinear dielectric response from the heating response of the ferroelectric films and the microwave nonlinear parameters of the ferroelectric films to be determined. It is shown that up to a specified value of microwave voltage amplitude the nonlinear response of BaxSr1−xTiO3 film capacitors can be predicted from the small signal capacitance–voltage characteristics. Formulas to estimate power handling capability connected with the field dielectric nonli...

A new physical model for a humidity-sensitive metal–insulator–semiconductor (MIS) capacitor with porous thin film is proposed. The model is used to determine water adsorption isotherm and calculate pore-size distribution of the film. The relative-humidity dependences of the capacitance and resistance of the film were measured. The effects of frequency on the dielectric constant of the film and the current of the MIS structure under various relative humidities were investigated.

Experimental and modeling results for resistance degradation in thin Ba0.5Sr0.5TiO3 (BST) film capacitors with platinum (Pt) electrodes are reported. The main experimental results are as follows. Under a constant applied voltage, the current density is observed to increase with time until it reaches a maximum value. Once the maximum value is reached, the current density becomes constant with time. The barrier height at the BST/Pt (cathode) interface is observed to decrease after prolonged electrical stressing. The resistance degradation effect is observed to be reversible, particularly at elevated temperatures. Based on the experimental results, a quantitative model for resistance degradation is proposed. In this model, the increase in the current density is attributed to a decrease in the barrier height at the cathode and this decrease is assumed to have a stretched exponential dependence on time. Using experimentally determined parameters, the model calculates the current density as a function of time at various temperatures. The calculated results are verified and the model is shown to be self-consistent. Hence the model provides an accelerated method for determining the lifetime of thin BST films at the operating conditions for advanced memory applications.

In earlier publications, we have demonstrated that La0.5Sr0.5CoO3 electrodes dramatically improve the phase stability and electrical properties of lead based ferroelectric capacitors. This study evaluates the influence of deviation from the cationic stoichiometry, La/Sr=1, on the ferroelectric properties. Polycrystalline Pb(Nb0.04Zr0.18Ti0.78)O3 based capacitors were fabricated with La0.5Sr0.5CoO3 as the bottom electrode and either La0.5Sr0.5CoO3 or La0.85Sr0.15CoO3 as the top electrode. The as-grown capacitors with La0.85Sr0.15CoO3 as the top electrode were slightly asymmetric about the voltage axis. However, the asymmetry did not increase when the capacitors were subjected to single side pulses and temperature. Both capacitor structures showed good fatigue (no fatigue up to 1011 cycles), retention, and imprint characteristics. Detailed pulse width and voltage dependent measurements were also carried out to further understand the impact of the change in electrode composition. The polarization values at 1...

In this paper, the extraction of doping profiles in ferroelectric thin-film capacitors using ferroelectric capacitance–voltage (CV) measurements is studied. For a ferroelectric field-dependent permittivity model, the doping profile relation to measured CV curves for ferroelectric thin-film capacitors is found to be analogous to the well-known result of metal–semiconductor Schottky junctions with an easily determined effective dielectric constant. Computer simulation shows the electrical doping concentration of ferroelectric thin-film capacitors can be profiled accurately with the proposed model. Limitations of the model are investigated.

Thin-film ferroelectric capacitors consisting of PbZr0.53Ti0.47O3 sandwiched between La0.5Sr0.5CoO3 electrodes have been deposited using pulsed laser deposition. The combination of oxidic perovskite-type materials results in capacitors with a coercive field (Ec) which is comparable with values for bulk ceramics. Textured thin-film capacitors with a columnar microstructure show lower switching voltages than epitaxial films. No thickness dependence of Ec and a good endurance up to 1011 cycles have been observed for epitaxial as well as textured capacitors with oxidic electrodes. In contrast, capacitors with a metallic top electrode show an increase of Ec with decreasing thickness of the ferroelectric layer. We show that charge injection can explain the experimentally observed increase of Ec with decreasing ferroelectric layer thickness. An overview is given of the growth conditions needed for PbZr0.53Ti0.47O3 films, because the precise stoichiometry is of the utmost importance for the capacitor quality. © 1997 American Institute of Physics.

Bi3.15Nd0.85Ti3O12 (BNdT) thin films were deposited on Pt∕Ti∕SiO2∕Si substrates using a sol-gel process. The film annealed at 750°C is composed of grains of 50–100nm in diameter. The fine grains show nearly random orientations. “Micropores” were frequently observed at the junctions of the grains and they are mostly amorphous, while sometimes containing very fine crystalline particles with sizes of only a few nanometers. The BNdT film capacitors with a Pt top electrode showed excellent ferroelectric properties. The remanent polarization and the coercive field were in the range of 41–43μC∕cm2 and 70–84kV∕cm, respectively. The BNdT capacitors did not show any significant fatigue up to 5×109 switching cycles at a frequency of 1MHz.

Strong space charge response is observed in SiC ceramic capacitors at low frequencies up to 0.1MHz. It leads to a dielectric constant of 2 910 000 at 100Hz. The critical temperature is observed near 773K. The losses decrease with increasing temperature. Strong frequency dependence of the dielectric properties is also detected. The SiC ceramic capacitor might be suitable as high-temperature by-pass capacitor in low voltage circuits.

We report on the measurement of switchable pulse polarization of micron and submicron ferroelectric capacitors contacted using an atomic force microscope. Fast square pulses with rise time on the order of tens of nanoseconds are used to obtain the switchable polarization (ΔP) of discrete polycrystalline Pb(ZrTi)O3 capacitors of 21.5, 0.69, and 0.19 μm2 prepared by sputtering and reactive ion etching. Our studies show that the switching characteristics of these capacitors are well behaved, indicating that high-speed and high-density ferroelectric memory capacitors are not limited by scaling down the capacitor area.

The electrical characteristics of SrTiO3/Al2O3 (160 nm up/90 nm down) laminated film capacitors using the sol-gel process have been investigated. SrTiO3 is a promising and extensively studied high-K dielectric material, but its leakage current property is poor. SrTiO3/Al2O3 laminated films can effectively suppress the demerits of pure SrTiO3 films under low electric field, but the leakage current value reaches to 0.1 A/cm2 at higher electric field (>160 MV/m). In this study, a new approach was applied to reduce the leakage current and improve the dielectric strength of SrTiO3/Al2O3 laminated films. Compared to laminated films with Au top electrodes, dielectric strength of laminated films with Al top electrodes improves from 205 MV/m to 322 MV/m, simultaneously the leakage current maintains the same order of magnitude (10−4 A/cm2) until the breakdown occurs. The above electrical characteristics are attributed to the anodic oxidation reaction in origin, which can repair the defects of laminated films at hig...

For Pb(ZrxTi1−x)O3 (PZT) thin‐film capacitors to be used in ferroelectric nonvolatile memories, they must have low polarization fatigue and low leakage currents. PZT capacitors fabricated in our laboratory with RuO2 electrodes exhibit excellent polarization fatigue characteristics, but they have large and variable leakage currents (typically 10−3–10−4 A/cm2 at 1 V). On the other hand, PZT capacitors with Pt electrodes have low leakage currents (typically

A significant increase in the efficiency of modern metallized film capacitors has been achieved by the application of special segmented nanometer-thick electrodes. The proper design of the electrode segmentation guarantees the best efficiency of the capacitor's self-healing (SH) ability. Meanwhile, the reported theoretical and experimental results have not led to the commonly accepted model of the SH process, since the experimental SH dissipated energy value is several times higher than the calculated one. In this paper, we show that the difference is caused by the heat outflow into polymer film. Based on this, a mathematical model of the metallized electrode destruction is developed. These insights in turn are leading to a better understanding of the SH development. The adequacy of the model is confirmed by both the experiments and the numerical calculations. A procedure of optimal segmented electrode design is offered.

Neodymium-doped Bi4Ti3O12 (BNT) films are evaluated for use as lead-free thin-film piezoelectrics in microelectromechanical systems. Bi4Ti3O12, Bi3.25La0.75Ti3O12, and Bi3.25Nd0.75Ti3O12 films were fabricated by chemical solution deposition on Pt/TiOx/SiO2/Si substrates. Nd substitution promoted random orientation with low (00l) diffraction peaks. The 1-μm-thick Bi3.25Nd0.75Ti3O12 film annealed at 750 °C exhibited a remanent polarization of 26 μC/cm2. Typical butterfly field-induced strain loops were obtained in the BNT film capacitors. The electrically induced strain is 8.4×10−4 under the bipolar driving field of 220 kV/cm. These results show that BNT is a promising candidate for use in lead-free thin-film piezoelectrics.

Fatigue-free 14 mol % La-modified PbTiO3 (PLT) thin films were grown on Pt/Ti/SiO2/Si substrates using pulsed-laser deposition and crystallized by furnace annealing at 600 °C. The 220-nm-thick PLT film capacitors with a Pt top electrode showed excellent ferroelectric properties. The remanent polarization (2Pr) and the coercive field (2Ec) were about 20 μC/cm2 and 70 kV/cm, respectively, and the PLT capacitors did not show any noticeable fatigue up to 3×109 read/write switching cycles at a frequency of 1 MHz and switching voltage of 5 V. By comparing the microstructures, electric, and dielectric properties with those of pure PbTiO3 thin films, the suppression of oxygen vacancies and/or charged defects, and the coral-like microstructures developed in PLT films were attributed to its fatigue-free feature.

Impedance spectroscopy measurements were carried out in situ on lead zirconate titanate capacitors 1.2×1.2 μm2 in size on a Samsung 4 Mbit 6 in, wafer. We show here that large dielectric loss appears at low frequencies, which is a constriction effect due to the porosity of the platinum electrode. Porous platinum electrodes facilitate an oxygen electrode reaction. The effect may be removed by annealing the platinum electrode at moderate temperature (300 °C). Such an anneal should thus be considered an essential step in the fabrication of a ferroelectric thin-film capacitor on Pt.

The capacitance of Pt/PbZr0.5Ti0.5O3/Pt capacitors versus the strength of applied ac electric field E has been measured for samples that fatigued at different square pulse switching cycles. Based on the in-series capacitor model, the variation of interface capacitance and bulk ferroelectric capacitance at different stages of fatigue were treated separately. A simplified method was derived to calculate the initial dielectric constant and Rayleigh constant for the bulk ferroelectric film from the ac electric field dependence of the sample capacitance. It was found that the initial dielectric constant and Rayleigh constant for the bulk ferroelectric film changed a little when the number of cycles is less than 3×106, whereas it decreased remarkably when the number of cycles is greater than 3×106. The suppression of polarization was attributed to pinning of the domain walls at the electrode/ferroelectric interface.

The measured switched polarization properties of integrated Pb(Zr,Ti)O3 (PZT) capacitors arrays have been found to show a small dependence on individual capacitor size in the range from 0.17 and 100 μm2. These thin (90 nm) PZT capacitors have low voltage switching properties with polarization saturation of

Fatigue-free and highly c-axis oriented Bi3.15Sm0.85Ti3O12 (BSmT) thin films were grown on Pt/TiO2/SiO2/Si(100) substrates using the method of metalorganic sol decomposition. The BSmT film capacitor with a top Pt electrode showed significantly improved values of the remanent polarization (2Pr) and the nonvolatile charge as compared to those of the Bi4−xLaxTi3O12 (x=0.75) film capacitor, recently known as the most promising candidate for nonvolatile memories. The 2Pr value of the BSmT capacitor was 49 μC/cm2 at an applied voltage of 10 V while the net nonvolatile switching charge was as high as 20 μC/cm2 and remained essentially constant up to 4.5×1010 read/write switching cycles at a frequency of 1 MHz. In addition to these, the capacitor demonstrated excellent charge–retention characteristics with its sensing margin of 17 μC/cm2 and a strong resistance against the imprinting failure.

Fatigue-free and highly c-axis oriented Bi3.25La0.75Ti3O12 (BLT) thin films were grown on Pt/Ti/SiO2/Si(100) substrates using metalorganic solution decomposition. Films annealed above 500 °C were characterized by strong c-axis preferential growth with an in-plane alignment of grains. The BLT film capacitors with a Pt top electrode showed excellent ferroelectric properties. The remanent polarization (2Pr) and the coercive field (Ec) were in the range of 26–28 μC/cm2and 50–75 kV/cm, respectively. More importantly, the BLT capacitors did not show any significant fatigue up to 3.5×1010 read/write switching cycles at a frequency of 1 MHz.

We have investigated the individual switching of nanoscale capacitors by piezoresponse force microscopy. Nanoscale epitaxial ferroelectric capacitors with terabyte per inch square equivalent density were fabricated by the deposition of top electrodes onto a pulsed laser deposited lead zirconate titanate thin film by electron beam evaporation through ultrathin anodic aluminum oxide membrane stencil masks. Using bias pulses, the nanoscale capacitors were uniformly switched and proved to be individually addressable. These film-based nanoscale capacitors might be a feasible alternative for high-density mass storage memory applications with near terabyte per inch square density due to the absence of any cross-talk effects. (C) 2010 American Institute of Physics. [doi:10.1063/1.3474960] Alexander von Humboldt Foundation (Y.K. and B.J.R.) KRCF through the project “Development of Advanced Industrial Metrology” German Science Foundation (DFG) Korean Research Foundation Author has checked copyright DM, 29/11/2013

Conduction has been studied in ultrathin nitrided oxide, re‐oxidized nitrided oxide, and nitrogen‐annealed nitrided oxide film capacitors in which the nitridation step was performed by a low‐partial‐pressure nitridation technique. Results indicate that, as well as some degree of barrier lowering due to the build‐up of nitrogen at the injecting interface, a trap‐assisted mechanism could be responsible for the enhanced conduction exhibited by the nitrided oxide devices. A simplified closed‐form trap‐assisted tunneling model is employed that produces a fit to the data with a trap depth of 2.1 eV. The difference between this trap model and a model requiring numerical integration was negligibly small (∼2%).

The degradation behavior of integrated Pt/SrBi2Ta2O9/Pt capacitors by hydrogen impregnation during the intermetal dielectric deposition and passivation is investigated. The hydrogen ions generated as a reaction byproduct from the SiH4-based deposition processes of the dielectric films induce reduction in the remanent polarization (Pr) as well as the imprint behavior of the small size capacitors (2×2 μm2). The degree of degradation is quite dependent on the size of the individual capacitors. The smaller capacitors underwent more serious degradation implying that the hydrogen ions impregnate into the SBT layer mainly along the etched side area of the capacitors not through the top Pt electrode. Metallization adopting TiN/Al/TiN/Ti multilayer is very effective in suppressing the hydrogen impregnation. In particular, the Ti layer appears to block the hydrogen penetration. Therefore, the optimized metallization scheme, wider metal lines than the top electrode area by 1 μm, successfully protects the integrated ...

We report on ferroelectric properties of polycrystalline sol-gel derived Pb(Nb, Zr, Ti)O3 (PNZT) thin films with SrRuO3 (SRO) electrodes. The processing temperature of the bottom electrode was varied between 550 and 850 °C. The polarization of the ferroelectric capacitors was dependent on the processing temperature of the bottom electrode. The capacitors exhibit low switching fields (40 kV/cm), high resistivity (1011 Ω cm at 3 V) and high remanent polarization values (19 μC/cm2 at 3 V), desirable properties for high-density ferroelectric memories. The activation field for these capacitors was measured to be ∼350 kV/cm and the polarization values exhibited a shallow dependence on the pulse width from 1 s to 1 μs. Fatigue, logic state retention, and dynamic imprint tests indicate robust capacitors from a memory viewpoint.

The rate of resistance degradation of thin (

The need for miniaturization without compromising cost and performance continues to motivate research in advanced capacitor devices. In this report, multilayer ceramic capacitors based on relaxor BaTiO3-Bi(Zn1/2Ti1/2)O3 (BT-BZT) were fabricated and characterized. In bulk ceramic embodiments, BT-BZT has been shown to exhibit relative permittivities greater than 1000, high resistivities (ρ > 1 GΩ-cm at 300 °C), and negligible saturation up to fields as high as 150 kV/cm. Multilayer capacitor embodiments were fabricated and found to exhibit similar dielectric and resistivity properties. The energy density for the multilayer ceramics reached values of ∼2.8 J/cm3 at room temperature at an applied electric field of ∼330 kV/cm. This represents a significant improvement compared to commercially available multilayer capacitors. The dielectric properties were also found to be stable over a wide range of temperatures with a temperature coefficient of approximately −2000 ppm/K measured from 50 to 350 °C, an important...

In this work, we demonstrate an approach to improve the recoverable energy-storage performance and piezoelectric response of 0.4Bi(Ni1/2Zr1/2)O3-0.6PbTiO3 (BNZ-PT) relaxor-ferroelectric film capacitors by utilizing the seeding layers engineering. Highly (100)-oriented BNZ-PT films were prepared through alternatively introducing PbO seeding layers, and the effects of PbO seeds on microstructure and electrical properties were investigated in details. Compared to the films without seeds, the PbO-seeded BNZ-PT films exhibit significant enhancement in dielectric and piezoelectric properties as well as energy-storage performance. The maximum energy-storage density of 56.1±2.4 J/cm3 and a piezoelectric coefficient as high as 125±10 pm/V have been achieved in the highly (100)-oriented BNZ-PT films at 2167 kV/cm, which are increased by 40.6% and 50.6% compared to the films without seeds, respectively. The observed tremendous enhancement of energy-storage performance and piezoelectric response can be attributed to ...

We report the activation field characteristics of (La,Sr)CoO3/Pb(Nb,Zr,Ti)O3/(La,Sr)CoO3 capacitors with areas varying from 13 to 9600 μm2. Switching properties such as maximum current and switching time depend on the capacitor area and measuring circuit elements, but the activation field is independent of capacitor area and measuring circuit parameters. Area independence of activation fields is also confirmed in (Pb,La)(Zr,Ti)O3 thin film capacitors. Two different approaches have been used to determine the activation field, yielding similar results. It is concluded that activation field is an intrinsic property and is a good quantitative measure of the ferroelectric switching properties.

In this letter, we report the results for capacitance versus frequency measurements on a set of Ba0.5Sr0.5TiO3 (BST) capacitors with platinum electrodes (Pt) and varying BST film thicknesses. The study shows that Pt/BST interfacial capacitance is independent of frequency whereas the bulk dielectric constant has a power law dependence on frequency. Also, the bulk dielectric constant is observed to decrease whereas the interfacial capacitance increases with increasing temperature. In addition, we report the dependence of dielectric dispersion on BST film thickness and temperature. Calculations are performed which provide insights into the observed dispersion effects.

Low-temperature (200 °C) sputter deposition of SrTiO3 (STO) thin films by using ultrahigh-density ceramic target enabled us to fabricate capacitors on polyimide-isoindroquinazoline dione (PIQ)- or benzocyclobutene (BCB)-coated alloy substrates. Complex impedances of the capacitors were analyzed. Capacitances of the 0.01 mm2 area capacitors with 200-nm-thick STO films were around 22 pF and were not dependent on frequency up to 8 GHz. Leakage-current densities of the films were lower than 10−6 A/cm2 at an applied voltage of 10 V and dielectric loss tangents were lower than 10−6.

The SrTiO3 ultrathin film capacitors were realized on Nb‐doped single‐crystal SrTiO3 substrates by chemical vapor deposition. The leakage current density of 10.4 nm thick SrTiO3 thin‐film capacitor was below 1×10−8 A/cm2 in the applied voltage range of −1.8 to +0.45 V, and its SiO2 equivalent thickness was 0.48 nm. The relative dielectric constant was over 160 for SrTiO3 thickness above 20 nm, but it decreased for SrTiO3 thickness below 20 nm. Dependence of leakage current on SrTiO3 film thickness was slight. These results could be explained by the existence of applied electric field concentration near the SrTiO3/electrode interface.

Fatigue of Pb(Zr0.52Ti0.48)O3 (PZT) thin‐film capacitors was studied under UV light (He‐Cd laser, λ=325 nm). The remanent polarization of the PZT film capacitors increased upon light illumination. Fatigue resistance was also improved under UV light. During fatigue test, the change in polarization of PZT films upon UV light illumination increased gradually with cycling. These results were examined within the framework of the polarization screening model, which is suggested as an essential process for fatigue. This leads to a conclusion that more charged defects are involved in the fatigue process through internal screening of polarization.

This letter discusses the reliability characteristics of metal‐oxide‐semiconductor capacitors with chemical‐vapor‐deposited Ta2O5 gate dielectric films. To be compatible with the conventional polycrystalline Si‐gate process, SiO2 or Si3N4 film was deposited on Ta2O5 as the top dielectric layer. It is found that under high‐field stress, interface state generation is enhanced with the presence of the top dielectric layers, probably due to the anode‐field increase caused by the positive‐charge buildup in the stacked dielectrics capacitors. The significant positive‐charge build‐up in capacitors with top dielectrics is believed to be due to the hole‐injection‐barrier from Ta2O5 to SiO2 or Si3N4 and/or damage creation in the Ta2O5 films.

Metal-Oxide-Semiconductor (MOS) capacitors with Bi2Te3 thin film sandwiched and embedded inside the oxide layer have been fabricated and studied. The capacitors exhibit ferroelectric-like hysteresis which is a result of the robust, reversible polarization of the Bi2Te3 thin film while the gate voltage sweeps. The temperature-dependent capacitance measurement indicates that the activation energy is about 0.33 eV for separating the electron and hole pairs in the bulk of Bi2Te3, and driving them to either the top or bottom surface of the thin film. Because of the fast polarization speed, potentially excellent endurance, and the complementary metal–oxide–semiconductor compatibility, the Bi2Te3 embedded MOS structures are very interesting for memory application.

The capacitive ferroelectric thermoelectric converter harvesting electrical energy through non-linear capacitance variation caused by changes in temperature is analyzed. The ferroelectric material used was the thin (0.5 μm) Ba0.3Sr0.7TiO3 film. On the basis of experimental dependencies of the ferroelectric film permittivity on temperature ranging from 100 K to 350 K under different electric fields up to 80 V/μm, the optimum values of operating temperatures and electric field for the energy harvesting optimization were determined. For the temperature oscillations of ±15 K around room temperature and electric field about 40 V/μm, the harvested energy was estimated as 30 mJ/cm3. It is shown that the use of thin ferroelectric films for rapid capacitance variation versus temperature and microelectromechanical systems for fast temperature modulations may be a relevant solution for creation of small power scale generators for portable electronics.