Breakdown Field Research Articles

Optimization of BaZr0.35Ti0.65O3 ferroelectric thin films on energy storage performance by adjusting annealing duration

BaZr0.35Ti0.65O3 (BZT35) ferroelectric thin films were synthesized via the sol-gel process. The phase, morphology and energy storage performance of BZT35 films of various annealing durations were studied, and the effect of annealing duration on these properties was thoroughly discussed. The size of grains in the film increases as the annealing duration prolongs, leading to an increased polarization strength. However, the breakdown field strength descends progressively with increasing annealing duration due to the increase in surface roughness. When annealed for 30 min, the film achieves the maximum polarization difference (16.1 μC/cm2) due to smaller grain size while maintaining good crystallinity, and a large breakdown field strength (3.9 MV/cm) because of its a dense structure and smooth surface. Consequently, this sample exhibits the optimal energy storage performance (Wrec = 31.54 J/cm³ and η = 91 %). The exceptional properties of BZT35 film suggest a promising application in energy storage.

Critical factors for enhancing electrical performance in LaGdO3 capacitor

This study investigates the characteristics of metal/LaGdO3/Si capacitors using LaGdO3 as the dielectric material. LaGdO3 thin films were deposited using radio-frequency magnetron sputtering, and the effects of different process parameters, such as annealing temperature, electrode materials, and oxygen ratio, on the capacitance characteristics were investigated. Results showed that the presence of oxygen vacancies affects the dielectric constant, flat-band voltage, and breakdown field of LaGdO3 films. The optimal annealing temperature for the LaGdO3/Si stack was identified to be 600 °C, resulting in a dielectric constant of 13.9 and a flat-band voltage shift of 0.1 V. Introducing 10 % O2 during deposition effectively repaired oxygen vacancies in the film, while excessively high oxygen proportions resulted in a lower dielectric constant and a higher flat-band voltage shift. Moreover, the electrode material was found to affect the capacitance characteristics. The dielectric constants for Al/LaGdO3/Si, Ti/LaGdO3/Si, and Pt/Ti/LaGdO3/Si capacitors were 10.0, 16.3, and 17.3, respectively. The flat-band voltage shifts were −0.7, −0.42, and −0.03 V, with hysteresis voltages of 345, 117, and 32 mV, respectively. The Pt/Ti/LaGdO3/Si device exhibited the lowest oxide defect density, indicating superior interface quality and potentially enhanced device performance. In addition, the band diagrams for metal/LaGdO3/Si were constructed. This study demonstrates that oxygen vacancies and electrode materials are crucial factors influencing the capacitance characteristics of LaGdO3 films. The electrical properties of LaGdO3 films can be effectively improved by controlling process parameters, enhancing their potential for applications in capacitors and other electronic devices.

Influence of Y2O3 Doping on Phase Evolution and Dielectric Characteristics of ZrO2 Ceramics.

Improvements in phase stability and dielectric characteristics can broaden the applications of zirconia in ceramics. Herein, a series of Y2O3-stabilized zirconia (YSZ) ceramics are synthesized using solid-state sintering, followed by an investigation into their phase evolution, grain size, dielectric constant, and breaking field. As the Y2O3 content increases from 0 wt% to 4 wt%, the as-grown YSZ ceramics undergo a distinct phase transformation, transitioning from monoclinic to monoclinic + tetragonal and further to monoclinic + tetragonal + cubic, before finally returning to monoclinic + cubic. Significant changes occur in the internal microstructure and grain size of the ceramics as the phase composition alters, resulting in a reduction in grain size from 3.17 μm to 0.27 μm. Moreover, their dielectric constants exhibit an increasing trend as the Y2O3 content increases, rising from 3.92 to 13.2. Importantly, the dielectric breakdown field of these YSZ ceramics shows a similar variation to the phase evolution, ranging from 0.11 to 0.15 MV/cm. This study sheds light on the phase evolution and dielectric properties of YSZ ceramics, offering an efficient strategy for enhancing their dielectric performances.

Synthesis of low-k SiONC thin films by plasma-assisted molecular layer deposition with tetraisocyanatesilane and phloroglucinol

Low-k SiONC thin films with excellent thermal stabilities were deposited using plasma-assisted molecular layer deposition (PA-MLD) with a tetraisocyanatesilane (Si(NCO)4) precursor, N2 plasma, and phloroglucinol (C6H3(OH)3). By adjusting the order of the N2 plasma exposure steps within the PA-MLD process, we successfully developed a deposition technique that allows accurate control of thickness at the Ångström level via self-limiting reactions. The thicknesses of the thin films were measured through spectroscopic ellipsometry (SE). By tuning the N2 plasma power, we facilitated the formation of –NH2 sites for phloroglucinol adsorption, achieving a growth per cycle of 0.18 Å cycle−1 with 300 W of N2 plasma power. Consequently, the thickness of the films increased linearly with each additional cycle. Moreover, the organic linkers within the film formed stable bonds through surface reactions, resulting in a negligible decrease in thickness of approximately −11% even upon exposure to a high annealing temperature of 600 °C. This observation was confirmed by SE, distinguishing the as-prepared film from previously reported low-k films that fail to maintain their thickness under similar conditions. X-ray photoelectron spectroscopy (XPS) and current–voltage (I–V) and capacitance–voltage (C–V) measurement were conducted to evaluate the composition, insulating properties, and dielectric constant according to the deposition and annealing conditions. XPS results revealed that as the plasma power increased from 200 to 300 W, the C/Si ratio increased from 0.37 to 0.67, decreasing the dielectric constant from 3.46 to 3.12. Furthermore, there was no significant difference in the composition before and after annealing, and the hysteresis decreased from 0.58 to 0.19 V owing to defect healing, while maintaining the leakage current density, breakdown field, and dielectric constant. The low dielectric constant, accurate thickness control, and excellent thermal stability of this MLD SiONC thin film enable its application as an interlayer dielectric in back-end-of-line process.

Enhancing the performance of SiC-based varistors through the use of SPS processing and fluxes

SiC varistors, which are used as surge arrestors in high power/high energy applications, often contain high levels of porosity (∼25 %) which can degrade varistor performance. Starting with SiC-clay varistors (∼43 µm grain size SiC) we employed spark plasma sintering (SPS) and flux additions (to enable liquid phase sintering) to reduce the level of porosity and understand its impact on the microstructure and the electrical properties. Sintering by SPS at 1200 °C for 5 min increased the density to 94 % theoretical, increasing energy density capability by almost a factor of 10 (to ∼1100 J cm−3), but the non-linear coefficient (α) fell by 40 % (to 3.5) and breakdown field (Eb) fell by 75 % (to ∼200 V cm−1). Varistors prepared with nepheline syenite as a flux (replacing clay) which were pressureless sintered at 1200 °C had maximum densities of 80 %. The samples in which all the clay was replaced by the flux exhibited exceptional energy density performance (over 10,000 J cm−3) but suffered reductions in other parameters. Using small grain size SiC (∼3 µm) and 40 % syenite flux yielded consistently superior properties: low power range α value 12.2, high power range α value 32.5, breakdown field ∼5880 (V cm−1) and very low leakage currents ∼10−3 (mA/cm2).

Impact of H-Related Chemical Bonds on Physical Properties of SiNx:H Films Deposited via Plasma-Enhanced Chemical Vapor Deposition

SiNx:H film deposition via plasma-enhanced chemical vapor deposition has been widely used in semiconductor devices. However, the relationship between the chemical bonds and the physical and chemical properties has rarely been studied for films deposited using tools in terms of the actual volume production. In this study, we investigated the effects of the deposition conditions on the H-related chemical bonding, physical and chemical properties, yield, and quality of SiNx:H films used as passivation layers at the 28 nm technology node. The radiofrequency (RF) power, electrode plate spacing, temperature, chamber pressure, and SiH4:NH3 gas flow ratio were selected as the deposition parameters. The results show a clear relationship between the H-related chemical bonds and the examined film properties. The difference in the refractive index (RI) and breakdown field (EB) of the SiNx:H films is mainly attributed to the change in the Si–H:N–H ratio. As the Si–H:N–H ratio increased, the RI and EB showed linear growth and exponential downward trends, respectively. In addition, compared with the Si–H:N–H ratio, the total Si–H and N–H contents had a greater impact on the wet etching rates of the SiNx:H films, but the stress was not entirely dependent on the total Si–H and N–H contents. Notably, excessive electrode plate spacing can lead to a significant undesired increase in the non-uniformity and surface roughness of SiNx:H films. This study provides industry-level processing guidance for the development of advanced silicon nitride film deposition technology.

Quantification of the strong, phonon-induced Urbach tails in β-Ga2O3 and their implications on electrical breakdown

In ultrawide bandgap (UWBG) nitride and oxide semiconductors, increased bandgap (Eg) correlates with greater ionicity and strong electron–phonon coupling. This limits mobility through phonon scattering, localizes carriers via polarons and self-trapping, broadens optical transitions via dynamic disorder, and modifies the breakdown field. Herein, we use polarized optical transmission spectroscopy from 77 to 633 K to investigate the Urbach energy (Eu) for many orientations of Fe- and Sn-doped β-Ga2O3 bulk crystals. We find Eu values ranging from 60 to 140 meV at 293 K and that static (structural defects plus zero-point phonons) disorder contributes more to Eu than dynamic (finite temperature phonon-induced) disorder. This is evidenced by lack of systematic Eu anisotropy, and Eu correlating more with x-ray diffraction rocking-curve broadening than with Sn-doping. The lowest measured Eu are ∼10× larger than for traditional semiconductors, pointing out that band tail effects need to be carefully considered in these materials for high field electronics. We demonstrate that, because optical transmission through thick samples is sensitive to sub-gap absorption, the commonly used Tauc extraction of a bandgap from transmission through Ga2O3 >1–3 μm thick is subject to errors. Combining our Eu(T) from Fe-doped samples with Eg(T) from ellipsometry, we extract a measure of an effective electron–phonon coupling that increases in weighted second order deformation potential with temperature and a larger value for E||b than E||c. The large electron–phonon coupling in β-Ga2O3 suggests that theories of electrical breakdown for traditional semiconductors need expansion to account not just for lower scattering time but also for impact ionization thresholds fluctuating in both time and space.

Hybrid mechanism of electrical breakdown in ferroelectric materials under high-pressure shock loading

The unique ability of ferroelectrics to generate high voltage under shock loading is limited by electrical breakdown within the shock-compressed ferroelectric material. Breakdown is a hybrid process of initiation and growth. The possible mechanisms of electrical breakdown in ferroelectric films and bulk ceramics subjected to high-pressure shock loading are discussed and experiments designed to elucidate which mechanisms govern breakdown. Gigapascal shock loading experiments were performed on poled Pb0.99(Zr0.95Ti0.05)0.98Nb0.02O3 ferroelectric film specimens in the range of 32–156 μm thickness to determine the dependence of the breakdown field on thickness and on film specimens in the range of 4–16 mm length to determine the dependence of the breakdown field on the duration of shock compression. The resulting breakdown-field vs thickness and breakdown-field vs shock transit time dependencies are consistent with a hybrid electron emission initiation and Joule heating microchannel growth mechanism. Further analysis of data previously obtained on shock-compressed 0.27Pb(In1/2Nb1/2)O3–0.47Pb(Mg1/3Nb2/3)O3–0.26PbTiO3 ferrvoelectric single crystals and Pb(Zr0.65Ti0.35)O3, Pb0.99(Zr0.52Ti0.48)0.99Nb0.01O3, Pb0.99(Zr0.95Ti0.05)0.98Nb0.02O3 bulk ceramics is consistent with this dual mechanism. It appears that neither chemical composition nor microstructure (single crystal vs polycrystalline) of the ferroelectric material has a significant effect on the breakdown mechanism in shocked ferroelectrics.

Mn doping as a simple strategy for improving energy storage in BaBi4Ti4O15 thin films

To obtain high energy storage density in ferroelectric films, polarization and breakdown field Eb are two crucial factors. The inversely coupled relationship between polarization and Eb is commonly observed and it remains a challenge to realize high Eb without deteriorating polarization. Selecting a suitable element doping should largely enhance the Eb since of the optimization of microstructures as well as the decrease in defects, meanwhile the doping should induce extra polarization contribution from lattice distortion. In this work, we reported that Eb can be largely enhanced via Mn doping in BaBi4Ti4O15 thin films due to grain refining, densification, and oxygen vacancy reduction. Interestingly, the polarization is not deteriorated since of the Mn doping effect induced extra polarization from the lattice distortion. Consequently, an ultrahigh energy storage density of 96 J/cm3 with a high efficiency of 76.6% was achieved in BaBi4Ti3.95Mn0.05O15 thin films with excellent stability and reliability. This work will provide a simple and effective route to improve the energy storage in dielectric capacitors.

Largely enhanced high‐temperature energy storage performance of P(VDF‐HFP) dielectric films via calcium niobate nanosheets

AbstractThe capacitive energy‐storage capacity of most emerging devices rapidly diminishes with increasing temperature, making high‐temperature dielectrics particularly desirable in modern electronic systems. In this work, calcium niobate (Ca2Nb3O10, CNO) nanosheets have been added into poly(vinylidene fluoride‐hexafluoropropylene) (P(VDF‐HFP), PVHP), forming PVHP/CNO nanocomposites with exceptional temperature stability and ultrahigh energy storage density. Especially, at 80°C and 450 MV/m, the PVHP/0.3 wt%CNO nanocomposite shows an excellent Wrec of 10.81 J/cm3 which is higher than previous PVDF‐based composite films at high temperatures. Because of the high dielectric permittivity of CNO nanosheets and the way that the parallel organization of the nanosheets blocks the course of electrical trees, nanocomposites exhibit greater dielectric constants and breakdown field strengths simultaneously. These findings, will be helpful in the development of flexible, high‐energy‐density capacitors that have stable performance at high temperatures.Highlights A record‐high high‐temperature Wrec is obtained. Excellent temperature stability from 25 to 80°C is achieved. The incorporation of Ca2Nb3O10 nanosheets significantly enhances Eb.

Microstructure, optical, dielectric, and nonlinear properties of Cd1-xBi2x/3Cu3Ti4O12 ceramics

Microstructure features along with optical, dielectric and nonlinear properties of Cd1-xBi2x/3Cu3Ti4O12 (x = 0, 0.3, 0.6, 0.9, and 1.0) ceramics were investigated systematically. With increase in Bi3+ doping content, Cd1-xBi2x/3Cu3Ti4O12 structure sightly distorted and eventually formed more stable configuration. Bi3+ doping also caused grain refinement and increased compactness of ceramics, whereas Bi-rich phase appeared at grain boundaries. Optical band gap (Eg) decreased due to increase in defect concentration. Dielectric loss (tanδ) dropped with increase in Bi3+ doping content while dielectric constant (ɛ′) remained high. The most optimal dielectric characteristics (the lowest tanδ of ∼0.033, giant ɛ′ of ∼10028 at 10 kHz and room temperature, the highest nonlinear coefficient (α of 4.62) and breakdown field strength (Eb of up to ∼9.23 kV/cm) were achieved at x = 0.9. Impedance spectra revealed semiconducting grains and insulating grain boundaries. Dielectric response evolution in Cd1-xBi2x/3Cu3Ti4O12 ceramics was described using internal barrier layer capacitor model. Electric modulus values indicated that low-frequency relaxation originated from grain boundaries. High energy barrier of grain boundaries was beneficial for enhancement of nonlinear properties of ceramics. Thus, Bi3+ doping improved both dielectric and nonlinear characteristics of Cd1-xBi2x/3Cu3Ti4O12 ceramics.

Defects and oxygen impurities in ferroelectric wurtzite Al1−xScxN alloys

III-nitrides and related alloys are widely used for optoelectronics and as acoustic resonators. Ferroelectric wurtzite nitrides are of particular interest because of their potential for direct integration with Si and wide bandgap semiconductors and unique polarization switching characteristics; such interest has taken off since the first report of ferroelectric Al1−xScxN alloys. However, the coercive fields needed to switch polarization are on the order of MV/cm, which are 1–2 orders of magnitude larger than oxide perovskite ferroelectrics. Atomic-scale point defects are known to impact the dielectric properties, including breakdown fields and leakage currents, as well as ferroelectric switching. However, very little is known about the native defects and impurities in Al1−xScxN and their effect on the dielectric and ferroelectric properties. In this study, we use first-principles calculations to determine the formation energetics of native defects and unintentional oxygen incorporation and their effects on the polarization switching barriers in Al1−xScxN alloys. We find that nitrogen vacancies are the dominant native defects, and unintentional oxygen incorporation on the nitrogen site is present in high concentrations. They introduce multiple mid-gap states that can lead to premature dielectric breakdown and increased temperature-activated leakage currents in ferroelectrics. We also find that nitrogen vacancy and substitutional oxygen reduce the switching barrier in Al1−xScxN at low Sc compositions. The effect is minimal or even negative (increases barrier) at higher Sc compositions. Unintentional defects are generally considered to adversely affect ferroelectric properties, but our findings reveal that controlled introduction of point defects by tuning synthesis conditions can instead benefit polarization switching in ferroelectric Al1−xScxN at certain compositions.

Magnetic field breakdown of electron hydrodynamics

Magnetic field breakdown of electron hydrodynamics

Superior energy storage performance achieved in tungsten bronze SBCN-based ceramics through tape-casting

Simultaneously integrating outstanding energy storage density and good energy storage efficiency in advanced ferroelectrics is crucial to implementing the application of dielectrics in high-power pulse devices. In this work, (Sr0.5Ba0.5)2Ca0.5Nb5-xSbxO15 ceramics were designed and prepared by adopting the B sites substitution engineering together with combining strategies of tape-casting method and two-step sintering process. Benefiting from the refined grain size and high density, the breakdown field of (Sr0.5Ba0.5)2Ca0.5Nb4.8Sb0.2O15 (SBCNS0.2) was promoted to 400 kV/cm. By the substitution of Sb5+ in the B sites, the weaker interaction force of Sb-O bond in BO6 octahedral polar unit induced the occurrence of polar nanoregions (PNRs) at room temperature to strengthen the dielectric relaxation behavior. Then it is noteworthy that SBCNS0.2 ceramics simultaneously obtained excellent recoverable energy density (Wrec, 3.9 J/cm3), energy storage efficiency (η, 90.5 %), power density (PD, 156.0 MW/cm3), and current density (CD, 1356.7 A/cm2). In addition, the SBCNS0.2 ceramics exhibited an ultrafast discharge time (t0.9, 67 ns). These results reveal prospective potential of unfilled tungsten bronze SBCNS0.2 ceramics in power capacitor applications and provide an effective strategy for improving excellent energy storage properties from the perspective of preparation methods.

Fully Integrated Direct Current Triboelectric Nanogenerators Coupled with Charge Pump and Electric Field Enhancing Effect Enabling Improved Output Performance

AbstractDirect‐current triboelectric nanogenerators (DC‐TENGs) arising from electrostatic breakdown have garnered significant attention due to their advantages of rectification‐free operation, constant current output, and high output power density. Previous studies have primarily concentrated on improving its performance through structural design and parameter optimization, neglecting the potential benefits of external charge excitation. Here, a facile and universal strategy coupling charge pump and electric field enhancing effect with DC‐TENG (CE‐DC‐TENG) is proposed to improve the output performance of DC‐TENG. An alternating current TENG is used as the charge pump. A field‐enhancing conductive layer, which is introduced under the main DC‐TENG, is connected with the pump TENG to accumulate the charge and enhance the electric field for electrostatic breakdown. The effectiveness of this method is demonstrated by linear and rotary sliding mode TENGs. Furthermore, a fully integrated rotary sliding mode CE‐DC‐TENG is designed and fabricated, and it exhibits impressive performance with a 13‐fold higher power density of 1.56 W m−2 compared to conventional DC‐TENG. Moreover, it can directly power small electronics or be combined with a designed power management circuit for more efficient energy conversion. This work presents a new design strategy for improving the performance of DC‐TENG and facilitating its practical applications.

Study on Breakdown Characteristics and Attenuation Characteristics of Air Mixed Gas

Abstract Nowadays, the global demand for environmental protection and energy saving is getting higher and higher. In the past, SF6 gas was regarded as an environmentally unfriendly gas in the circuit breaker with SF6 gas as the insulating medium. In order to save energy and reduce emissions, this paper uses clean and environmentally friendly air as the arc extinguishing medium. The gas mixture studied contains N2, O2 and CO2. Through two approximate values of Boltzmann equation, we obtain the electron energy distribution function of air mixed gas under different electric field reduction conditions. By studying the changes of ionization and adsorption coefficients of particles under various collision conditions, we obtained the conversion breakdown field strength (E/N) Cr of air mixture. An arc attenuation model is built to characterize the arc attenuation characteristics using the prior transport characteristics as input. The arc attenuation process is broken down into three steps: heat recovery, pre-ignition, and arcing. All of these phases are determined by the changes in axial temperature and arc conductance over time. Analysis is done on the air and nitrogen thermal recovery and pre-dielectric recovery phases. This study explores the use of clean dielectrics to ensure optimum performance of primary equipment in the power system, based on current circumstances.

Giant electrocaloric effect and breakdown field strength in ferroelectric terpolymer nanocomposites by morphologically diverse nanostructures

Electrocaloric cooling is a method for flexible electronics and compact chips with a promising ability to subvert traditional vapor compression refrigeration technology. Nevertheless, most reported EC materials exhibit relatively low adiabatic temperature (ΔT) and low breakdown field strength (Eb) at room temperature, limiting their further applications. Here, we develop a ferroelectric nanocomposite, composed of relaxor terpolymer poly(vinylidene fluoride-trifluoroethylen-chlorofluoroethylene) (PVTC), ceramic nanofillers [0.68(BaZr0.2Ti0.8O3)-0.32(Ba0.7Ca0.3TiO3)] (BCZT), boron nitride nanosheets (BNNSs), and BiFeO3 nanofibers (BFO NFs) with different morphologies and vary components ratios. The most optimal 12BBBP nanocomposite demonstrates gigantic ECE values including an isothermal entropy change (ΔS) of 94.5 J·kg−1·K−1 and a ΔT of 13.5 K under 220 MV/m electric field at 303 K, ΔS and ΔT are 3.5 times and 2.2 times larger than PVTC under 100 MV/m. It also exhibits an excellent Eb with a value of 290 MV/m. The phase-field simulation is used to simulate Eb behavior of nanocomposites with fillers of different nano-morphologies under an electrostatic field. Simultaneously, the interfacial coupling and ferroelectric domain structures are also simulated based on the time-dependent Landau-Ginzburg-Devonshire (TLGD) theory through finite element analysis (FEA) to present a better explanation for ECE performance. The experimental and simulation results simultaneously denote the ferroelectric nanocomposite possesses outstanding ECE and high Eb performance, laying foundation for the ferroelectrics in fields of flexible electronics and compact chip cooling. Coupled with the facile processability of terpolymer and lead-free nature of electroactive ceramics, this work paves a new way to develop a scalable, environmentally friendly and high-performance EC materials for next generation of refrigeration.

Relaxation and energy storage properties of NaNb0.98Ta0.02O3 modulated (Na0.5Bi0.5)0.935Sr0.065TiO3 ceramics

Dielectric capacitors with excellent power density and rapid charge-discharge rates have received significant attention in the field of pulsed power. In this study, anti-ferroelectric NaNb0.98Ta0.02O3 was doped into (Na0.5Bi0.5)0.935Sr0.065TiO3 ceramics, resulting in a substantial improvement of the integrated energy storage performance of the ceramics. Multiscale testing confirmed that the ceramic system formed a dense solid solution with a single-phase perovskite structure. Increasing the content of NaNb0.98Ta0.02O3 effectively enhances the relaxation and energy storage properties of the ceramics, while reducing average grain size improves their breakdown field strength, leading to excellent electrical properties at 30 kV/mm field strength when x = 0.2 for this ceramic system - exhibiting recoverable energy storage density Wrec = 7.98 J/cm3 and energy storage efficiency η = 90 %. Furthermore, it demonstrates excellent stability over a wide frequency range (5–90 Hz): Wrec = 7.97 ± 2 % J/cm3, η = 89 ± 1 %; as well as stability over a wide temperature range (30–200 °C): Wrec = 7 ± 2 % J/cm3, η = 89 ± 1 %, along with a rapid charging-discharging rate t0.9 = 0.32 μs. These outstanding properties indicate great prospects for future applications of this ceramic system in the field of energy storage capacitors.

Engineering multi-ion doping by entropy for high energy storage density with high efficiency in amorphous thin film

In the field of stored energy materials, lead-free amorphous thin films have the advantages of high breakdown strength, excellent stability, environmental protection and pollution-free, and are a very competitive energy storage material. However, the difficulty of simultaneous optimization of polarization and breakdown strength has always been a difficulty in improving the energy storage properties of amorphous thin films. Entropy can be used to design multi-ion doping to improve the energy storage performance of amorphous film. Amorphous films with different entropy are prepared by sol-gel method doped with 50 % Zr4+ and 5 %, 10 %, 15 %, 20 % Bi(Mn0·5Ti0.5)O3. The Bi0·1Ba0·85Sr0·05Mn0·05Ti0·45Zr0·5O3 amorphous thin film prepared at medium entropy (S = 1.37) has a recoverable energy storage density of 107.4 J cm−3 at 8.42 MV cm−1, and the energy storage efficiency is 93.9 %. Under the interaction of multiple elements, entropy design can give full play to the advantages of composite effects, improve breakdown field strength and energy storage efficiency, and is a new method to enhance energy storage performance.

InN/InAlN heterostructures for new generation of fast electronics

N-polar InN/In0.61Al0.39N heterostructures are grown directly on sapphire by using metalorganic chemical vapor deposition. The thickness of Mg-doped In0.61Al0.39N is 340 nm, and the root-mean-square surface roughness of 20 nm thick InN is ∼3.2 nm. An optional AlN spike grown at 710 °C for 35 s is used either as an interlayer to separate the InAlN buffer from the InN channel or as a part of InAlN nucleation after sapphire nitridation. High-resolution transmission electron microscopy reveals approximately two monolayers of AlN if used as the interlayer. In this case, the concentration of screw and edge threading dislocations in partially strained InN decreased down to 6.5 × 109 and 38 × 109 cm−2, respectively. More importantly, the interlayer inclusion suppressed remote donor and alloy disorder scatterings, providing, at room temperature, the InN free electron mobility and concentration of 620 cm2/V s and 3 × 1013 cm−2, respectively. On the other hand, omitting the AlN spike by InAlN nucleation led to structural deteriorations while buffer resistivity increased to 1.7 kΩ/□. A current density of ∼12–16 A/mm, breakdown field of ∼75 kV/cm, and electron drift velocity of ∼2 × 107 cm/s were determined in InN by applying 10 ns voltage pulses on fabricated test resistors.