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A novel GaN current-aperture vertical electron transistor (CAVET) with an energy band pinning (EBP) structure (EBP-CAVET) is proposed and investigated by simulations. The EBP-CAVET is featured with hybrid contacts on the p-GaN layer, locally having Ohmic contact combined with Schottky gate metals in the longitudinal direction. The Ohmic contact is shorted to the source electrode and the Schottky gate metals are shorted to the gate electrode. The conduction band (E c) in the gate region is modulated by the alternately arranged contacts. In the Ohmic contact region, E c remains a fixed value, which acts as an energy band pinning and suppresses the variation of the E c in the gate region. In the on-state (V GS > 0 V) and blocking-state with high V DS , the EBP structure inhibits the E c shifting downwards in the gate region to achieve a high threshold voltage (V th), a low leakage current density (J dss), and a high breakdown voltage (BV). In the reverse conduction state (V DS < 0 V & V GS ≤ 0 V), the EBP structure suppresses the E c shifting upwards to achieve a low and independent of gate bias reverse turn-on voltage (V RT). The proposed EBP-CAVET achieves a high V th of 2.10 V, a V RT of 0.69 V, a low J dss of 3.1 × 10−11 A/cm2 at V DS = 1000 V, a high BV of 1660 V. Compared with an integrated Schottky barrier diode or fin diode in a field effect transistor (FET), the EBP structure occupies a much smaller chip area. Thus, the EBP-CAVET achieves a low specific ON-resistance (R on,sp) of 1.19 mΩ cm2 and an extremely high power-figure-of-merit (PFOM) up to 2.32 GW/cm2. Consequently, the proposed structure presents a new design concept and enhances the application potential for GaN CAVET with high V th and low reverse conduction loss. • A novel GaN CAVET with an energy band pinning structure (EBP-CAVET) is proposed to improve the forward characteristic and reverse conduction characteristic. • In the reverse conduction (V SD > 0V, V GS ≤ 0V),the EBP-CAVET realizes a low V RT and the V RT is independent of V GS. • The proposed EBP-CAVET achieves a high V th of 2.10 V, a lower J dss of 3.1 × 10−11 A/cm2, and a higher BV of 1660 V. • Since the EBP structure occupies a minimal chip area, the EBP-CAVET achieves a low R on,sp of 1.19 mΩ cm2 and an extremely high PFOM up to 2.32 GW/cm2. [ABSTRACT FROM AUTHOR]

The overpoling effect of alternating current poling (ACP) was studied on [001]-orientated rhombohedral Pb(Mg1/3Nb2/3)O3-0.26PbTiO3 (PMN-0.26PT) single crystals. Our experimental results showed that the property enhancement from the ACP was remarkable only when the poling cycle number (NL) was kept low. When ACP was continued after the saturation, dielectric and piezoelectric properties gradually dropped down to traditional direct current poled levels or even lower. Such a decrease in material properties caused by the large NL during ACP was defined as the "overpoling effect of ACP" in this study. The following lattice symmetry and domain structure characterization studies were performed through x-ray diffraction (XRD) and piezoelectric force microscopy (PFM) to find the origin of the overpoling effect. The XRD measurements combined with temperature dependence of dielectric properties demonstrated that the field-induced phase transition continued when the samples became overpoled. Further PFM measurements illustrated that the domain density of the overpoled ACP sample was significantly lower than that of the normal one, while the "2R" domain configuration was maintained through the ACP process. In addition, the hysteresis loop characterization indicated large decreases in the coercive fields. The discovered overpoling effect of ACP could help us understand the mechanisms of ACP and optimize the ACP process. [ABSTRACT FROM AUTHOR]

Alternating current poling (ACP) was performed on Gen III relaxor-PT Mn-doped Pb(In1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3 (Mn: PIN-PMN-PT) single crystals with the poling direction of [001]. Experimental results proved that ACP could bring property enhancement to both k31 and k33 mode crystals. Compared to those from traditional direct current poling (DCP), ACP with the optimized conditions (20 kV/cm, 0.1 Hz, and 20 cycles) enhanced the dielectric and piezoelectric properties of k31-mode mode crystals by more than 30%, where the enhanced free dielectric constant and piezoelectric coefficient d33 reached 5300 and 1750 pC/N, respectively. Furthermore, replacing DCP with ACP could increase the advantages of Gen III relaxor-PT. The coupling factors k31 and k33 were enhanced to 0.472 and 0.915, the mechanical quality factor Qm was enhanced by 17%, and the depoling temperature was raised by 17 °C to 123 °C. In the following mechanism study, in situ x-ray diffraction (XRD) combined with the temperature-dependent dielectric constant measurement proved the introduction of the monoclinic phases after ACP, while piezoresponse force microscopy (PFM) observation showed "2R"-like "2M" domain morphologies in ACP single crystals. Both these intrinsic and extrinsic factors are believed to be the keys to the mechanisms of property enhancement behind ACP. This study proved that ACP is an effective property enhancement method suitable for Gen III relaxor-PT single crystals and will promote its applications in high-temperature and high-power devices. [ABSTRACT FROM AUTHOR]

(1- x)Pb(Mg 1/3 Nb 2/3)O 3 - x PbTiO 3 (PMN-PT) single crystals, especially with compositions near its morphotropic phase boundary (MPB), have been employed for a broad range of applications such as ultrasound transducers, sensors, and actuators. To further enhance the properties of PMN-PT, electrode patterning, as a method of domain engineering, was proved to be an effective approach. In our previous report, a 200 nm grating pattern electrode (Ti/Au–MnO x) (nano-electrode) was prepared on one surface of PMN-PT crystal, exhibiting 30% d 33 enhancement. In this work, the multi-layered domain morphology and the domain engineering from nano-electrode were characterized using piezoresponse force microscopy (PFM). A hypothetical domain engineering model for nano-electrodes is established to explain the experimental results as well as the property enhancement from the nano-electrode. The electrode patterning proves that the nano-scale modification can tune the macro-scale piezoelectric properties of the bulk material. Image, graphical abstract Nano-patterned composite electrode (Nano-electrode) , as a method of domain engineering, exhibits 30% d 33 enhancement on (1- x)Pb(Mg 1/3 Nb 2/3)O 3 - x PbTiO 3 (PMN-PT) single crystal. In this work, the mechanism of the property enhancement is studied through the multi-layered domain morphology by piezoresponse force microscopy (PFM). A hypothetical domain engineering model for nano-electrodes is established in the end. [ABSTRACT FROM AUTHOR]

Alternating current (electric field) poling (ACP) was applied on [001]-oriented 0.7Pb(Mg1/3Nb2/3)O3-0.3PbTiO3 (PMN-0.3PT) single crystal samples with dimensions of 5 × 1.25 × 1.25 mm3 (with electrodes on the 1.25 × 1.25 mm2 surfaces), and the influence of ACP frequency (fACP) was studied. Compared to those from traditional direct (electric field) poling samples, the piezoelectric coefficient (d33) and free dielectric constant (εT33/ε0) of ACP samples could gain up to a 67% increase to 3200 pC/N and 10 500, respectively. The influence of fACP was studied on two main aspects: saturated properties and dynamic saturation process. In general, ACP samples with lower fACP had higher saturated d33, εT33/ε0, and coupling factor k33, as well as lower dielectric loss and faster saturation speed. The ACP dynamics during the saturation process were studied by measuring the polarization-vs-electric field hysteresis loops (P-E loops). The P-E loops illustrated that the coercive field of ACP samples could be further tuned from 1.84 kV/cm to 3.03 kV/cm by changing fACP (0.1–10 Hz). This work demonstrated the enormous potential of ACP optimization in relaxor-PT single crystal-based low-frequency transducer applications. [ABSTRACT FROM AUTHOR]

Abstract X-ray diffraction (XRD) reciprocal space mapping (RSM) was used to investigate how nanograted electrodes affect the nanodomain distribution and average crystal structure in near-surface regions of poled Pb(Mg 1/3 Nb 2/3)O 3 -30%PbTiO 3 (PMN-30PT) single crystals. The RSM scans revealed a transverse broadening along the (H00) direction, which was quite different from that of either the rhombohedral (R) or monoclinic A (M A) phase. This broadening provides evidence of a non-uniform distribution of tilt angles between neighboring nanodomains, induced by a gradient in the applied electric field (E). Investigations of the front and back surfaces of the crystals revealed significant differences in the RSM scans. Gradients in the domain distribution and apparent symmetry may extend throughout the crystal thickness. The data evidence changes in the nanodomain distribution that results in adaptations of the average symmetry. Graphical abstract Image 1 [ABSTRACT FROM AUTHOR]

In this work, the piezoelectric and dielectric properties of [001]-oriented 0.7Pb(Mg1/3Nb2/3)O3-0.3PbTiO3 single crystals under alternating current poling (ACP) at different temperatures were studied. The piezoelectric coefficients (d33 ∼ 1930 pC/N, d31 ∼ −850 pC/N) and free dielectric permittivity (εT33/ε0 ∼ 7570) reached their highest values when the poling temperature (Tpoling) was 70 °C. Compared with traditional direct current electric field poling at 20 °C, 70 °C-ACP samples showed an enhancement of 40%, 35%, and 49% for d33, d31, and εT33/ε0, respectively. Meanwhile, d33 and εT33/ε0 were enhanced by about 9% when Tpoling increased from 20 °C to 70 °C under ACP, while d31 remained the same value and the dielectric loss was lowered from 0.29% to 0.22%. Moreover, ACP samples with different Tpoling have similar electromechanical coupling factors (k31 ∼ 0.44, kt ∼ 0.60). A discussion of the mechanism for the ACP enhancement was based on the domain observation using piezoresponse force microscopy, and the results showed that the domain densities of ACP samples with different Tpoling were positively correlated with their piezoelectric properties. This work demonstrated the enormous potential of ACP optimization for relaxor-PT single crystal applications. [ABSTRACT FROM AUTHOR]

Diffuse scattering and relaxor behavior in Na0.5Bi0.5TiO3 (NBT) and NBT-5.6 at. %BaTiO3 (NBT-5.6%BT) were investigated. X-ray diffraction revealed two types of diffuse scattering in NBT: (i) broad and (ii) asymmetric L-shaped. After modification with 5.6%BT, the broad diffuse scattering patterns became narrow, and the asymmetric L-shaped ones were replaced by symmetric ones. The symmetric diffuse scattering in NBT-5.6%BT disappeared with increasing dc electric field (E) for E ≥ 9.5 kV/cm where the frequency dispersion in the dielectric constant disappeared. These results demonstrate that the relaxor characteristics are directly correlated with the diffuse scattering and the presence polar nano-regions. [ABSTRACT FROM AUTHOR]

The crystallographic dependence of the DC electric (E) field induced strain and phase transition in Na0.5Bi0.5TiO3-5.6%BaTiO3 (NBT-5.6%BT) single crystals has been investigated. An induced transition between pseudocubic and tetragonal structures was observed under E = 10 kV/cm for fields applied along the <001> direction, whereas an induced transition between pseudocubic and rhombohedral structures was observed when the E-field was applied along <111>. Our results show near the morphotropic phase boundary that the phase stability of NBT-x%BT is dependent on the crystallographic direction along which E was applied. [ABSTRACT FROM AUTHOR]

With the great success on verifying its effectiveness on relaxor-PbTiO3 (PT) single crystals (SCs), alternating current poling (ACP) has been taking a center as a new domain engineering method in the last few years. Compared with the conventional direct current poling (DCP), ACP enables enhanced piezoelectric and dielectric properties. In this article, research progress in ACP and perspectives are introduced. Initially, optimized conditions of ACP for relaxor-PT SCs and unsolved issues on polycrystalline ceramics and spurious modes are reviewed. Second, the ferroelectric domain size dependence of piezoelectricity associated with ACP is discussed. We hypothesize that a tradeoff between domain and domain wall contributions exists for high piezoelectricity, suggesting an optimum 109° domain wall size, which is presumably dependent on compositions, crystallographic symmetries, and domain configurations. Finally, crystals synthesized by a solid-state crystal growth (SSCG) method are briefly introduced due to their unprecedented piezoelectricity obtained by ACP (${d}_{33} \sim 5500$ pC/N). We hope that this work helps to grasp the current status of ACP and to guide future tasks to be studied. [ABSTRACT FROM AUTHOR]

Additionally, the supplementary paragraph on page 4 of the published article should be corrected to cite Fig. "See the supplementary material for the detailed property enhancement from ACP (Table S1); the effect of different f SB ACP sb on the saturated properties (Fig. Chang, Y. Yamashita, A. R. Paterson, J. Jones, and X. Jiang, Appl. Phys. [Extracted from the article]

Sliver-mode 0.73Pb(Mg 1/3 Nb 2/3)O 3 -0.27PbTiO 3 single crystals were poled by the alternating current electric field (ACP) along the [001] direction for low-frequency transducer applications. Under ACP with optimized conditions (2.89 kV rms , 0.1 Hz, 10 cycles), the free dielectric constant (ε T 33 / ε 0) was enhanced from 5300 to 7220 and piezoelectric coefficient (d 33) was improved from 1410 to 1920 pC/N, both are about 36% higher than those under traditional direct current poling. The piezoresponse force microscopy observation and phase-field simulation show the similar domain morphologies evolution. During the ACP process, the domain morphology first changes from '4R' to '2R' configuration, and then the length of the 109° domain wall keeps increasing, which leads to a longer range of ordering and a stable lamellar domain structure in the end. The correlation between the domain morphology and the coercive field is also found in both the experiment and simulation. These findings on the effect and mechanism of ACP will help develop advanced low-frequency single crystal transducer arrays. Evolution of domain structures of rhombohedral PMN-PT during ACP process was studied through the domain morphology tracking, which developed from '4R' to '2R' configuration. The results also show a good correlation between coercive field and domain structure, attributing to a new domain engineering model. [Display omitted] [ABSTRACT FROM AUTHOR]

Dielectric tunability in [001] and [110] oriented Na0.5Bi0.5TiO3-5.6%BaTiO3 crystals was investigated as functions of temperature and frequency. A tunability of the dielectric constant as high as 58% and 46% was obtained at room temperature under an electric field of E = 20 kV/cm applied along [001] and [110]. Our findings demonstrate that Na0.5Bi0.5TiO3-5.6%BaTiO3 crystals are potential voltage-tunable materials. (© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

The dielectric, ferroelectric, and electric field-induced strain response of [001]-and [101]-oriented 0.944Na0.5Bi0.5TiO3-0.056BaTiO3 (0.944NBT-0.056BT) single crystals were investigated as a function of temperature and dc bias (E). An ultrahigh electromechanical response with large amplitude longitudinal piezoelectric coefficients as high as d33 = 2500 pm/V was found in [001]PC oriented 0.944NBT-0.056BT single crystals near a depolarization temperature of Td = 130 °C. In-situ XRD revealed that the enhanced piezoelectric properties resulted from a polarization extension between a polar pseudocubic phase with a slight tetragonal (P4bm) distortion and a polar tetragonal one with a large tetragonal distortion of c/a = 1.02. Our findings indicate a potential approach to high performance lead-free piezoelectrics, via polarization extension. [ABSTRACT FROM AUTHOR]

We propose a piezoelectric–piezoresistive coupling electric field sensor capable of performing large dynamic range AC electric field measurements. The electric field sensor utilizes direct coupling between piezoelectric (PE) materials and piezoresistive (PR) strain gauges, in conjunction with an external signal conditioning circuit, to measure AC electric fields effectively. We verified the feasibility of the scheme using a finite element simulation, fabricated a prototype of the electric field sensor, and characterized the properties of the prototype. The testing results indicate that the sensor exhibits an ac resolution of 50 V/m and a linear measurable electric field range of 0 to over 200 kV/m, which keeps the linearity at less than 0.94% from 1 Hz to over 5 kHz. Furthermore, the sensor also has advantages, such as a small size and low power consumption. The sensor can enhance the comprehensive observability and measurability of digital power grids. [ABSTRACT FROM AUTHOR]

This paper presents the design, fabrication, and testing of a dual-resonance acoustic emission (AE) sensor based on PMN-PT single crystal for partial discharge (PD) detection. The use of high-performance PMN-PT single crystal enhances the sensor sensitivity. Resonance peak coupling is utilized to increase the bandwidth of the sensor effectively. The effects of piezoelectric vibrator size, vibrator spacing, and external circuitry on the sensor output are analyzed using equivalent circuits and finite element models (FEM) for sensor design. After calibration, the self-made sensor has a peak sensitivity of 76.4 dB and a bandwidth of 20 kHz to 150 kHz, which meets the demand of PD detection. The PD detection experiments verify that the self-made sensors can accurately detect PD with a high signal-to-noise ratio of 15.8 dB. In the end, the reliability test proves that the sensors have good stability and temperature characteristics. Besides above sensor's performance improvement, our design has the great potential to reduce the sensor's cross section, resulting better suitability on curved surfaces. The feasibility of employing PMN-PT as a replacement for PZT in the fabrication of AE sensors is proven by these good test results. [Display omitted] • Utilize high-performance PMN-PT single crystal to enhance sensor sensitivity to 76.4 dB. • Employ resonance peak coupling to expand the sensor bandwidth, covering 20 kHz to 150 kHz. • Devise an original matching layer design method for low-frequency, wide-bandwidth applications. • Homemade sensors achieve high reliability and can detect partial discharge accurately with higher SNR. [ABSTRACT FROM AUTHOR]

The change in the electrical properties of 4H-SiC Schottky barrier diodes (SBDs) irradiated by 6 MeV Au ions at low temperature (LT) is investigated. The SBDs are characterized by current–voltage (I-V) and capacitance–voltage (C-V). The SRIM software is used to calculate the Au ion transportation process. The experimental results indicate that the ideality factor (n) and the reverse leakage current (I R) increase, and Schottky barrier height (SBH) decreases with the increase in fluence. It is found that series resistance (R S) and effective impurity concentration (N D) are recovered at 5 × 1015 ions/cm2. Calculation results show that the mental layer can prevent most of the Au ions, while the secondary particles will enter the SiC layer. Therefore, these results demonstrate that the secondary particles induce many defects at the metal-SiC interface and the SiC epitaxial layer after LT heavy ion (HI) irradiation. [ABSTRACT FROM AUTHOR]