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We present a novel method of modeling the contact between a metal and a two-dimensional semiconductor. Using Au on MoS 2 as an example, we self-consistently solve the Schrödinger and Poisson equations and obtain the charge density in the contact. We consider open boundary conditions using the quantum transmitting boundary method and model the electron current through the contact region. We then investigate the effect of effective Schottky barrier height, electrostatic doping, and length of the overlap region on the contact resistance in a top contact geometry. By using data from experiments or from ab initio calculations for the fitting of parameters, such as the effective Schottky barrier height, the model can be used to efficiently obtain the contact resistance and, therefore, the quality of the contact. Furthermore, we investigate the effect of sampling of the Brillouin zone in the transverse direction on the numerical calculation of key quantities, such as contact resistance and free charge density. Additionally, we show that the boundary conditions applied to the Poisson equation during the calculation of the free charge density have a significant impact on the calculated contact resistance and that the impact is more pronounced in heterostructures with a larger Schottky barrier. We found that the contact resistance may be significantly underestimated, by up to one order of magnitude, when the height of the simulation domain is not large enough. [ABSTRACT FROM AUTHOR]

Aqueous zinc ion batteries provide new solutions for achieving environmentally friendly and safe energy storage devices. Unfortunately, the further application is hampered by the growth of zinc dendrites caused by uneven zinc deposition, hydrogen evolution and other side interfacial reactions at the zinc anode. Herein, a multifunctional Bi‐Bi2O3 hybrid artificial interface layer is constructed on the surface of the zinc anode using an in situ conversion reaction. Among them, the Bi‐Bi2O3 Schottky structure not only significantly accelerates the migration of Zn2+ through its built‐in electric field, but also effectively improves the hydrogen evolution barrier (ΔGH*), thereby suppressing side reactions. Moreover, the Schottky contact formed between the interface layer and the metal zinc interface also regulates the electronic distribution state on the zinc surface and optimizes the deposition process of Zn2+, ensuring a more uniform and orderly zinc deposition process. Based on the synergistic effect of dual Schottky junctions, symmetric batteries achieve stable cycling for 2000 h under the conditions of 1.0 mA cm−2 and 1.0 mAh cm−2. The full cell assembled with α‐MnO2 as the cathode maintains capacity of 112.7 mAh g−1 after 1000 cycles at 1 A g−1 with a capacity retention rate of 84%. [ABSTRACT FROM AUTHOR]

Band gap engineering based on doped two‐dimensional (2D) transition metal dichalcogenides (TMDs) has shown great potential in the design and development of new nano photoelectronic devices and their application in photoelectrocatalysis. However, there are two key issues that are difficult to take into account, namely the impurity levels induced by dopant atoms appear in the forbidden band of the doping system, which can become the recombination center of photogenerated carriers, thereby reducing the photocatalytic efficiency. Compared with the carrier mobility of the corresponding doped systems, that of intrinsic 2D TMDs is too low. Understanding the doping mechanism of heteroatoms in these systems and designing corresponding crystal structures rationally is important for solving these problems. In this study, the crystal structures of co‐doped monolayer WS2 with Nb and Re atoms were designed using density functional theory, and doping systems with graphene (high carrier mobility) were assembled into a heterostructure using the concept of heterorecombination. The N‐P type co‐doping of Nb and Re atoms retained the continuous band characteristics of the original monolayer WS2 while also providing the high carrier mobility of graphene, yielding an excellent multipurpose material for manufacturing high‐speed Schottky devices and efficient water‐splitting H evolution catalysts. [ABSTRACT FROM AUTHOR]

For the construction of metal-semiconductor heterojunctions, the rational regulation of Schottky barriers has an important impact on their photocatalytic activity. Here, we successfully constructed Pd-loaded Al: SrTiO 3 (ASTO) photocatalysts by an in situ strategy, and the photocatalytic hydrogen production performance was conducted under simulated solar light irradiation. The results show that the optimal Pd-ASTO-1.5% photocatalyst exhibits a hydrogen production performance of 1.43 mmol g−1 h−1, which is a 140-fold improvement compared to pure ASTO. Density functional theory (DFT) calculations demonstrate that Pd nanoparticles (NPs) could reduce the energy barrier for hydrogen adsorption. In addition, the optimal Schottky barrier not only accelerates the charge dynamics through the driving force of the Schottky junction but also prevents the flow of electrons trapped by Pd NPs back to ASTO, which greatly improves the interfacial carrier separation efficiency for photocatalytic hydrogen production under simulated solar light irradiation. This work reveals key insights into the construction of Schottky heterojunctions in the field of photocatalytic hydrogen production. [Display omitted] • Pd-loaded Al: SrTiO 3 (ASTO) photocatalysts were prepared by an in situ strategy. • The optimal Schottky barrier accelerates the charge dynamics from ASTO to Pd NPs. • The optimal Pd-ASTO-1.5% photocatalyst exhibited a hydrogen rate of 1.43 mmol g−1 h−1. • DFT calculations showed that Pd NPs reduced the energy barrier for hydrogen adsorption. • The Schottky junction prevents the flow of electrons trapped by Pd NPs back to ASTO. [ABSTRACT FROM AUTHOR]

Molybdenum disulfide (MoS2) is a representative two-dimensional layered transition-metal dichalcogenide semiconductor. Layer-number-dependent electronic properties are attractive in the development of nanomaterial-based electronics for a wide range of applications including sensors, switches, and amplifiers. MoS2 field-effect transistors (FETs) have been studied as promising future nanoelectronic devices with desirable features of atomic-level thickness and high electrical properties. When a naturally n -doped MoS2 is contacted with metals, a strong Fermi-level pinning effect adjusts a Schottky barrier and influences its electronic characteristics significantly. In this study, we investigate multilayer MoS2 Schottky barrier FETs (SBFETs), emphasizing the metal-contact impact on device performance via computational device modeling. We find that p -type MoS2 SBFETs may be built with appropriate metals and gate voltage control. Furthermore, we propose ambipolar multilayer MoS2 SBFETs with asymmetric metal electrodes, which exhibit gate-voltage dependent ambipolar transport behavior through optimizing metal contacts in MoS2 device. Introducing a dual-split gate geometry, the MoS2 SBFETs can further operate in four distinct configurations: p − p, n − n, p − n, and n − p. Electrical characteristics are calculated, and improved performance of a high rectification ratio can be feasible as an attractive feature for efficient electrical and photonic devices. [ABSTRACT FROM AUTHOR]

Amorphous aluminum oxide a-Al2O3 deposited by atomic layer deposition (ALD) is widely used in nonvolatile memory devices. In this paper, the leakage current dependence on the ALD synthesis temperature is investigated by six charge transport models: Schottky effect, thermally assisted tunneling at a contact, Frenkel effect, Hill-Adachi model of overlapping Coulomb potentials, Makram-Ebeid and Lannoo multiphonon isolated trap ionization model, and Nasyrov–Gritsenko model of phonon-assisted tunneling between neighboring traps. It is shown that the leakage current exponentially increases with the ALD synthesis temperature, which is related to the increase in trap concentration. [ABSTRACT FROM AUTHOR]

Flexible capacitive pressure sensors play a crucial role in wearable electronics and robotics. However, their susceptibility to environmental noise poses challenges to sensing precision. To mitigate the impact of environmental influences, a sensor capable of producing signals orders of magnitudes larger than the noise becomes essential. One straightforward method to enhance capacitance values involves reducing the thickness of the dielectric layer. Yet, when this reduction reaches nanometer scale, the dielectric layer may become mechanically vulnerable and more importantly, their charge storage capability is compromised due to electron tunneling. To address these challenges, here the naturally formed alumina (Al2O3) on aluminum (Al) surface is employed as a stable and ultra‐thin dielectric layer. Simultaneously, the Schottky effect at the Al‐Al2O3‐carbon black (CB) interface is harnessed to prevent electron tunneling. These strategies collectively yielded a large unit‐area capacitance (UAC) of 50 nF cm−2 and demonstrated high electrical and environmental stability. Furthermore, hollow hemispherical microstructures are incorporated at the interface, resulting in a flexible pressure sensor with high sensitivity (8.6 kPa−1) and a linear response up to 50 kPa. With its simple two‐layer structure, this sensor can be seamlessly integrated in situ and offers commercial‐grade resolution at mN‐level for monitoring human biomechanical signals. [ABSTRACT FROM AUTHOR]

We have examined the transition from the thermionic to the space-charge limited current (SCLC) regime under strong Schottky effects as the electric field increases. We have used the methodology of Lau et al. for their study of the transition from the field emission (FE) to the SCLC regime. We have obtained current–voltage, I–V, characteristics, exhibiting both an exponential and a power-law part signifying the presence of the transition. We have found that this transition does not occur at all temperatures but there is a range of temperatures and work functions for which it takes place. Furthermore, the diode width plays a crucial role. As the field is increased, the emitting material may enter first the FE regime before it transitions to the SCLC regime. The condition that the emitter remains within the thermal regime before it transitions to the SCLC regime places restrictions on the operating temperature T and work function W of the emitter. However, we observe the thermionic to the SCLC transition for all thermionic diodes with work functions 1 eV ≤ W ≤ 2 eV (which includes all modern thermionic cathodes), but the diode widths must be in a specific (but extended) range which includes the nm range. [ABSTRACT FROM AUTHOR]

Memristors have attracted considerable attention as next-generation devices for logic and neuromorphic computing applications, owing to their high on/off current ratio, low power consumption, and high switching speed. Despite the various excellent characteristics of memristors, they suffer from unstable conductive filament-based switching when applied in real-world applications. To address this issue, the effects of Schottky barrier modulation on device performance, in terms of conduction and failure mechanisms of an Ag/WOx/p-Si memristor, were investigated in this study by varying the silicon (Si) doping concentration. Through the temperature analysis of I–V characteristics, different conduction mechanisms are observed according to the doping concentration and resistance state. Moreover, endurance failure with several doping concentrations is analyzed by using filament overgrowth phenomena. The results of this study are expected to help in the development of devices with characteristics suitable for application. [ABSTRACT FROM AUTHOR]

Hydrogen production by water electrolysis has attracted much interest in the field of renewable energy storage due to its high efficiency and low environmental impact. Catalytic activity of transition metal-based electrode materials can be effectively improved by adjusting their composition and/or structure. In this study, MXene nanosheets are electrophoretically deposited on foamed nickel (MXene/NF), and further coated by NiCo layered double hydroxides (LDH) nanosheets, also by electrophoresis, to obtain the heterostructured and highly conductive NiCo LDH/MXene/NF electrode, highly active in the hydrogen evolution reaction. Uniform surface distribution of three-dimensional interconnected nanosheets is demonstrated by SEM and TEM. The electrode surface is fully wet within 150 ms, indicating excellent hydrophilicity. The highly conductive NiCo LDH/MXene/NF electrode material exhibits a potential overshoot of 123 mV vs. RHE at a current density of 10 mA cm−2, with a Tafel slope of +86.6 mV dec−1. Long-term cyclic testing confirms good stability of the newly prepared electrode material in the hydrogen evolution reaction. • The abundant polar functional groups of MXene can also facilitate water adsorption. • Modulate the surface electron density of NiCo LDH/MXene/NF heterostructure by the Schottky effect. • MXene nanosheets were deposited onto NF via electrophoretic deposition. [ABSTRACT FROM AUTHOR]

Optoelectronic logic gates have emerged as one of the key candidates for the creation of next generation logic devices. However, current optoelectronic logic gates can provide only one or two logic gates, severely limiting their applications. Here we report a self‐powered and mechanically flexible device based on a BaTiO3 ferroelectric film to produce multi‐modal logic gates. By exploiting the photo‐induced photovoltaic and pyroelectric effects of a Schottky junction which is created between BaTiO3 and LaNiO3, the device is able to provide five different optoelectronic logic gates, which can be operated using input lasers of different wavelength (405 or 785 nm). The mode of operation of the logic gate can be switched by controlling the wavelength and intensity of the input laser, where the switching process is both lossless and reversible. A logic gate array was designed to conduct the five logic operations, with 100% accuracy, thereby providing application potential for the Internet of Things, big data, and secure solutions for data processing and transmission. [ABSTRACT FROM AUTHOR]

This work reports the dielectric behavior of the biopolymer ethyl cellulose (EC) observed from transient currents experiments under the action of a direct current (DC) electric field (~107 V/m) under vacuum conditions. The viscoelastic response of the EC was evaluated using dynamic mechanical analysis (DMA), observing a mechanical relaxation related to glass transition of around ~402 K. Furthermore, we propose a mathematical framework that describes the transient current in EC using a fractional differential equation, whose solution involves the Mittag–Leffler function. The fractional order, between 0 and 1, is related to the energy dissipation rate and the molecular mobility of the polymer. Subsequently, the conduction mechanisms are considered, on the one hand, the phenomena that occur through the polymer–electrode interface and, on the other hand, those which manifest themselves in the bulk material. Finally, alternating current (AC) conductivity measurements above the glass transition temperature (~402 K) and in a frequency domain from 20 Hz to 2 MHz were carried out, observing electrical conduction described by the segmental movements of the polymeric chains. Its electrical properties also position EC as a potential candidate for electrical, electronics, and mechatronics applications. [ABSTRACT FROM AUTHOR]

Using a quantum mechanical calculation, we investigate the fundamental limitations of the Schottky emission (SE) model for its applications to electron injection into dielectrics from a metal or semiconductor electrode. This work covers a wide range of electric fields from 0.01 to 10 MV/cm and a large temperature span with many barrier height values (ΦB). We conclude that the SE model is only applicable for a very small class of dielectrics under 0.1 MV/cm and at high temperatures over ∼330 K. For many defective dielectrics with large barrier heights (ΦB ≥ ∼1.5 eV) in back-of-line/middle-of-line/metal–insulator–metal capacitor applications, the corresponding electric fields for the measurable currents far exceed 0.1 MV/cm, and up to 10 MV/cm, the application of the SE model is likely invalid so that the extracted ΦB values may not be correct. We provide a quantitative guide to avoid future misapplications of the SE model. [ABSTRACT FROM AUTHOR]

In this paper, a theoretical model of the propagation of a shear horizontal wave in a piezoelectric semiconductor semi-infinite medium is established using the optimized spectral method. First, the basic equations of the piezoelectric semiconductor semi-infinite medium are derived with the consideration of biased electric fields. Then, considering the propagation of a shear horizontal wave in the piezoelectric semiconductor semi-infinite medium, two equivalent mathematical models are established. In the first mathematical model, the Schottky junction is theoretically treated as an electrically imperfect interface, and an interface characteristic length is utilized to describe the interface effect of the Schottky junction. To legitimately confirm the interface characteristic length, a second mathematical model is established, in which the Schottky junction is theoretically treated as an electrical gradient layer. Finally, the dispersion and attenuation curves of shear horizontal waves are numerically calculated using these two mathematical models to discuss the influence of the Schottky junction on the dispersion and attenuation characteristics of shear horizontal waves. Utilizing the equivalence of these two mathematical models and the above numerical results, the numerical value of the interface characteristic length is reliably legitimately confirmed; this value is independent of the thickness of the upper metal layer, the doping concentration of the lower n-type piezoelectric semiconductor substrate, and biasing electric fields. Only the biasing electric field parallel to the Schottky junction can provide an evident influence on the attenuation characteristics of shear horizontal waves and enhance the interface effect of the Schottky junction. Since the second mathematical model is also a validation of our previous mathematical model established through the state transfer equation method, some numerical results calculated using these two mathematical models are compared with those obtained using the previous method to verify the correctness and superiority of the research work presented in this paper. Since these two mathematical models can better calculate the dispersion and attenuation curves of high-frequency waves in micro- and nano-scale piezoelectric semiconductor materials, the establishment of mathematical models and the revelation of physical mechanisms are fundamental to the analysis and optimization of micro-scale resonators, energy harvesters, and amplifications. [ABSTRACT FROM AUTHOR]

Hydrogen storage in chemicals is regarded as one of the sustainable techniques for tackling the energy-related challenges. However, hydrogen production from ammonia borane (NH3BH3, AB) is restricted by the inherent activity of metallic catalysts, which may be boosted by light irradiation. Herein, Pd-doped Co nanoparticles (NPs) were incorporated into a Zr-MOF composite composed of MXene-derived Ti3C2 nanosheets and UiO-66-NH2 (denoted as TUNS) by a double-solvent approach, obtaining a CoPd@TUNS composite. The optimized Co30Pd@TUNS composite exhibited outstanding catalytic activity for the complete dehydrogenation of AB within 0.6 min under 300 W Xe lamp light, with a high turnover frequency of 130.37 molH2 (molmetal)−1 min−1 at 298 K. The activity of Co30Pd@TUNS increased 10-fold under light irradiation as compared to that in the dark. For photocatalytic dehydrogenation, Co30Pd@TUNS was more active than Co30Pd@UiO-66-NH2 and Co30Pd/Ti3C2. Its excellent performance might be attributed to multiple factors including the photo-harvesting MOF generating electron–hole pairs, Ti3C2 nanosheets promoting the charge separation, and the Schottky effect facilitating electron migration to metal NPs for activating the substrate via an electron-deficient BH3 moiety, along with the attack of photogenerated hydroxyl radicals and water molecules. Moreover, the kinetic study manifested that AB dehydrogenation is a zero-order reaction with regard to the substrate. The great stability and recyclability of Co30Pd@TUNS was also confirmed after 5 runs. This study would widen a pathway for the design of an efficient MOF-based catalyst for hydrogen generation in the energy-related field. [ABSTRACT FROM AUTHOR]

Flower-like ZnO nanorods were successfully synthesised using a template-free, lowtemperature chemical bath deposition method. The effects of growth time on the structural, morphological, and vibrational properties of flower-like zinc oxide were investigated. X-ray diffraction (XRD) and scanning electron microscopy (SEM) indicated that the crystallite size and density of flower-like ZnO nanorods increased with increasing growth time. Raman spectroscopy confirmed the existence of specific Raman modes that correspond to the wurtzite structure of ZnO. In addition, Raman measurements revealed that increased growth time increases the Raman modes intensity of the flower-like ZnO nanorods. Moreover, the measurements of the Au/ZnO nanorods/FTO Schottky diode showed that all devices functioned as Schottky diodes and rectifying; however, their ideality factor was greater than 1. In addition to the ideality factor, the Schottky barrier height was calculated and slightly increased with growth time. The values of Schottky barrier height obtained were 0.502 eV, 0.523 eV, 0.516 eV and 0.529 eV for samples grown at 1, 2, 3 and 4 h, respectively. [ABSTRACT FROM AUTHOR]

Chlorine-based gases are used for the reactive ion etching (RIE) of β − Ga 2 O 3. However, the effects of Cl-plasma on the electronic properties of β − Ga 2 O 3 are not known. In order to shed light on this topic, we carried out an experimental and theoretical study on β − Ga 2 O 3 epilayers treated with Cl 2 / Ar or BCl 3 / Ar plasma. We found four traps in the 0.2–0.8 eV energy range below the conduction band edge ( E C ). Two of these, located at E C -0.24 eV and E C -0.28 eV, arise only when the epilayers are treated with BCl 3 / Ar. While the involvement of Cl in their microscopic structure is not discarded, the possibility that these two levels might have an intrinsic nature seems more plausible. Our findings might explain the reported effects on the Schottky barrier diodes of β − Ga 2 O 3 when RIE is employed during processing. [ABSTRACT FROM AUTHOR]

Space charge accumulation in polymer is a key problem for the electrical aging of insulation under DC condition. Space charge accumulation is strongly determined by the charge injection rate. The estimation of charge injection with steady state current contains the extraction current and is not accurate. This paper proposes a quantitative estimation method of the charge injection at the metal/polymer interface with space charge and current simultaneous measurement. A double-layer sample with a blocking layer is employed to make a quasi-unipolar condition to remove the extraction current. In addition, the displacement current is removed by considering the change in electric field on the electrode. The relationship between the electrode electric field and the pure injection current is analyzed. It is found that the square root of electric field intensity and the logarithm of injection current at the Al/LDPE (low density polyethylene) interface are linear with each other. The coefficients β for negative and positive charge injection at Al/LDPE interface are about 8.44 × 10−24 and 8.32 × 10−24, respectively. It indicates that both negative and positive charge injection at Al/LDPE interface fit the mathematical relationship of the Poole–Frenkel effect, rather than the Schottky effect which is mostly used in the study on the charge transport at polymer/metal. The negative and positive charge injection barriers are 1.23 and 1.24 eV, respectively. [ABSTRACT FROM AUTHOR]

Shear horizontal (SH) waves propagating in a metal substrate covered with a transversely isotropic piezoelectric semiconductor thin film is analyzed in the present paper. The Schottky junction, which is created by the metal and the n-type piezoelectric semiconductor with a higher Fermi level, can be seen as an electrically gradient layer between the substrate and the thin film. The transfer matrix of the Schottky junction is derived by using Magnus series expansion and approximate laminated medium methods, respectively. The influences of the Schottky junction, semiconductor coupling, doping density, and electric boundary conditions on the dispersion and attenuation and the first three wave modes are discussed via numerical example. It reveals that numerical results obtained by these two methods are well matched and the existence of Schottky junction has less influence on the dispersion of SH surface wave although, but evidently influences on the attenuation. In particular, the mode shapes of electric potential, electric displacement, carrier perturbation density, and the electric current density are affected evidently by the existence of Schottky junction. [ABSTRACT FROM AUTHOR]

Atomically thin layered materials such as MoS2 have future versatile applications in low power electronics. Here, we demonstrate the growth of a salt-assisted large scale, high-quality monolayer MoS2 toward the realization of a high-performance hysteresis-free field-effect transistor (FET). Density functional theory calculations are implemented to monitor the effects of the Schottky barrier and metal-induced gap states between our metal electrodes and MoS2 for achieving high carrier transport. The role of absorbed molecules and oxide traps on the hysteresis are studied in detail. For the first time, a hysteresis-free intrinsic transistor behavior is obtained by an amplitude sweep pulse I–V measurement with varying pulse widths. Under this condition, a significant enhancement of the field-effect mobility up to 30 cm² V−1 s−1 is achieved. Moreover, to correlate these results, a single-pulse time-domain drain current analysis is carried out to unleash the fast and slow transient charge trapping phenomena. Our findings on the hysteresis-free transfer characteristic and high intrinsic field-effect mobility in salt-assisted monolayer MoS2 FETs will be beneficial for future device applications in complex memory, logic, and sensor systems. [ABSTRACT FROM AUTHOR]

The bulk magnetization, magnetocaloric effect, and heat capacity of polycrystalline NdFe0.5Mn0.5O3 have been studied in the temperature range of 1.5–300 K. The magnetic entropy change (Δ S M) shows a peak near 7 K at 100 kOe with a value of ∼7.22 J kg−1 K−1. Another magnetic entropy change is also observed between 0 and 40 kOe near the spin reorientation region of Fe3+/Mn3+ ions (∼45 K), wherein the entropy change gets suppressed with increasing field. The magnetic heat capacity shows a broad hump near the Néel temperature (∼250 K). Around 5 K, a step-like feature in heat capacity due to the Schottky effect is observed which is associated with the crystal field effects in Nd3+ ions. [ABSTRACT FROM AUTHOR]

In this work, we investigate the effect of different chemical treatments, such as solvents, bases, and acids, on the surface properties and electrical behavior of Schottky diodes fabricated on metalorganic chemical vapor deposition-grown, n-type, N-polar GaN. The I–V and C–V barrier heights of the as-grown Schottky diodes are found to be 0.40 eV and 0.60 eV, respectively, with an ideality factor n = 1.07. It is found that the solvent treatments neither change the surface nor the electrical performance of the Schottky diodes, as expected. However, the treatments by the alkaline photolithography developer and acid—the latter of which is often used to clean the surface of Ga-polar GaN films prior to metal contact deposition—degrade the performance of N-polar GaN. These base and acid treatments severely roughen the surface by creating triangular/hexagonal crystallographic facets. The I–V and C–V barrier heights of these base- and acid-treated diodes are increased to 0.63 eV and 1.00 eV, respectively, with ideality factor values n < 1.2. X-ray photoelectron spectroscopy studies indicate that base- and acid-treated surfaces have lower oxygen content as compared to the as-grown sample surface. It is understood that the increment in the barrier height for base- and acid-treated diodes could be due to the change in polarity, from N-polar to semi-polar/non-polar, on these crystallographic features. All these results demonstrate that, unlike for Ga-polar GaN, the N-polar GaN surface is highly reactive to bases and acids. [ABSTRACT FROM AUTHOR]

We report the lateral and vertical electrical conduction properties of PdCrO2 thin films grown on insulating Al2O3 (001) and conducting β-Ga2O3 (2 ¯ 01) substrates. The c-axis oriented PdCrO2 films on the both substrates showed metallic temperature dependence of in-plane resistivity down to 2 K. In PdCrO2/β-Ga2O3 vertical devices, rectifying current density–voltage (J–V) characteristics revealed the formation of a Schottky barrier at the PdCrO2/β-Ga2O3 interface. The Schottky barrier height (SBH) of 1.2–1.8 eV, evaluated by J–V characteristics, is significantly larger than 0.8 eV expected from the usual Mott–Schottky relation based on the electron affinity of β-Ga2O3 (4.0 eV) and the work function of PdCrO2 (4.8 eV) determined by ultraviolet photoelectron spectroscopy. The enhanced SBH at the PdCrO2/β-Ga2O3 interface indicates the existence of interface dipoles, as in the case of PdCoO2/β-Ga2O3. Besides, we observed a large difference of the SBH between the J–V measurements (1.2–1.8 eV) and capacitance measurements (2.0–2.1 eV). While the SBH is definitely enhanced by the interface dipole effect, the level of enhancement at the PdCrO2/β-Ga2O3 interface is rather inhomogeneous, different from that at the PdCoO2/β-Ga2O3. In fact, two typical types of interfaces were found by a high-angle annular dark-field scanning transmission electron microscope, which would be the origin of the inhomogeneous SBH. Further understanding of the interface formation between delafossite oxides and β-Ga2O3 (2 ¯ 01) will improve the performance of Ga2O3 Schottky junctions as a power diode available at high temperatures. [ABSTRACT FROM AUTHOR]

Bright, red electroluminescence is generated in reverse biased Schottky barrier diodes (SBDs) based on β-Ga2O3 single crystals codoped with chromium and silicon. It is due to intracenter transitions of octahedrally coordinated Cr3+ ions excited by electron impact in the depletion layer of the diodes. The electroluminescence spectrum around 700 nm in wavelength is nearly identical to the spectrum of the well-known photoluminescence of Cr3+ in β-Ga2O3, which is featured by the two lines R1 and R2. In contrast to the photoluminescence, however, in the electroluminescence, each of the R1 and R2 lines is additionally split by 1.5–3 meV. Since the R1/R2 lines correspond to transitions from two Kramers-degenerate states (split 2E excited state) to the ground state 4A2, this splitting cannot be ascribed to the normal Stark effect in the strong electric field of the Schottky barrier diode's depletion layer. Instead, we explain the splitting by the pseudo-Stark effect that occurs because the Cr3+ ions replace Ga3+ at two kinds of energetically equivalent octahedral sites that differ crystallographically by an inversion at the Cr ion. Superposition of the dominating R1 doublet radiation would result in a tunable beat frequency of about 0.4–0.7 THz and might be utilized for a terahertz light source. Moreover, the electroluminescence of chromium is representative of the ability to excite the luminescent states of other transition metals. Hence, high temperature light-emitting SBDs in different colors are a potential application for β-Ga2O3. [ABSTRACT FROM AUTHOR]

In a high-vacuum diode, the volt–ampere characteristic of the thermionic emission of Na+ with surface of NaxAu intermetallide. Its hysteresis was found, which is associated with changes in the surface NaxAu caused by the action of an external electric field. In accordance with the Schottky effect, analysis of the current–voltage characteristic and the value of the work function of the NaxAu surface was estimated. Suggested mechanism of thermionic emission of Na+ from the surface of NaxAu. [ABSTRACT FROM AUTHOR]

Due to their low cost and excellent electrocatalytic performance, nickel-based hydroxides are widely used as hydrogen evolution catalysts for large-scale hydrogen production by water electrolysis. In this study, a heterostructured composite with improved electron transport and modulated electron surface density was prepared by combining Ni(OH)2 with two-dimensional layered Ti3C2Tx (Ti3C2Tx-MXene). Ni(OH)2 nanosheets were formed on nickel foam (NF) substrates using acid etching, followed by the longitudinal growth of negatively charged Ti3C2Tx-MXene on positively charged Ni(OH)2/NF via electrophoretic deposition. The resulting structure facilitates spontaneous electron transfer from Ti3C2Tx-MXene to Ni(OH)2/NF by means of the Mott–Schottky heterostructure effect and establishes a continuous electron transport path which effectively increases the concentration of active sites, improving hydrogen evolution during water electrolysis. The obtained electrode is characterized by an HER overpotential of 66 mV (vs. RHE) and a Tafel slope of +105 mV dec−1 at a current density of 10 mA cm−2, combined with good electrochemical stability. [ABSTRACT FROM AUTHOR]

Nanoelectromechanical systems (NEMS) of 2D nanomaterials are potent exploration devices for high‐sensitive mechanical coupling, mass testing, and biosensing. Nevertheless, the internal interference from the multiple resonant states easily causes the deviation and overlap of the target signal. Here, an oxidized‐MXene resonant system performs the unique response peak at the fundamental frequency f0,1 of 3.37 ± 0.04 MHz within the ultrawide frequency up to 400 MHz, due to the ferroelectric‐conductive structure. This unique resonant peak can effectively avoid the dispute of indistinguishable vibratal states. The resonator exhibits advanced performances with a large dynamic range of 70.41 ± 0.15 dB and low thermomechanical motion spectral density of 669 fmHz$669\;\frac{{{\rm{fm}}}}{{\sqrt {{\rm{Hz}}} }}$. The molecular sensing mechanisms of the oxidized‐MXene system are systematically studied to achieve repeatable detection with high mass resolution (low to 8.00 ± 0.01 × 10‐19 g). These consequences can afford potential guidelines for the NEMS devices in terms of the credible and legible sensors for ultra‐accurate and interference‐free measurements. [ABSTRACT FROM AUTHOR]

Ti 3 C 2 MXene/CdIn 2 S 4 Schottky heterojunctions were constructed by a solvothermal method, showing the highly photocatalytic efficiencies for H 2 production and Cr(VI) reduction under visible light, owing to the synergistic effect of Schottky heterojunction and S vacancies. [Display omitted] Developing efficient heterojunction photocatalysts that have a high charge carrier separation rate and improved light-harvesting capacity is a crucial step in solving energy crisis and reducing environmental pollution. Herein, we synthesized few-layered Ti 3 C 2 MXene sheets (MXs) by a manual shaking process, and combined with CdIn 2 S 4 (CIS) to construct novel Ti 3 C 2 MXene/CdIn 2 S 4 (MXCIS) Schottky heterojunction through a solvothermal method. The strong interface between two-dimensional (2D) Ti 3 C 2 MXene and 2D CIS nanoplates led to enhanced light-harvesting capacity and promoted charge separation rate. Additionally, the presence of S vacancies on the MXCIS surface helped to trap free electrons. The optimal sample, 5-MXCIS (with 5 wt% MXs loading), exhibited outstanding performance for photocatalytic hydrogen (H 2) evolution and Cr(VI) reduction under visible light due to the synergistic effect of enhanced light-harvesting capacity and charge separation rate. The charge transfer kinetics was thoroughly studied using multiple techniques. The reactive species of •O 2 −, •OH and h+ were generated in 5-MXCIS system, and e− and •O 2 − radicals were found to be the main contributors to Cr(VI) photoreduction. Based on the characterization results, a possible photocatalytic mechanism for H 2 evolution and Cr(VI) reduction was proposed. On the whole, this work provides new insights into the design of 2D/2D MXene-based Schottky heterojunction photocatalysts for boosting photocatalytic efficiency. [ABSTRACT FROM AUTHOR]

Combining the strong localized surface plasmon resonance (LSPR) of metallic Ag and the chemically reactive Pt co-catalyst, the Ag–Pt bimetallic composite was prepared and then coated on the surface of the exfoliated defective graphitic carbon nitride nanosheets (C 3 N x NS) for plasmon hot electron-mediated photocatalytic H 2 evolution. Under the visible light irradiation, the sample of (1:2) Ag–Pt/C 3 N x NS exhibits the highest activity (1.25 mmol g−1 h−1), which is 35.7 and 1.7 times higher than that of Ag/C 3 N x NS and Pt/C 3 N x NS, respectively. Moreover, the apparent quantum efficiency (AQE) of (1:2) Ag–Pt/C 3 N x NS reaches 3.3% at 420 nm. The boosted photocatalytic capacity may be ascribed to the utilization of the advantages of the LSPR effect of Ag particles and the Schottky barrier between Pt and C 3 N x NS, resulting in more electrons participate in the reduction reaction to boost the photocatalytic H 2 evolution performance. [Display omitted] • Ag–Pt core-shell structure was deposited on the exfoliated defective C 3 N x nanosheets. • The Core Ag shows LSPR effect and the shell Pt acts chemically reactive co-catalyst. • The (1:2) Ag–Pt/C 3 N x NS exhibits the highest H 2 evolution rate (1.25 mmol g−1 h−1). • The AQE of the sample of (1:2) Ag–Pt/C 3 N x NS reaches 3.3% at 420 nm. • The boosted activity was attributed to the LSPR effect and the Schottky barrier. [ABSTRACT FROM AUTHOR]

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Developing Ohmic contact systems or achieving low contact resistance is significant for high‐performance semiconductor devices. This work comprehensively investigates the interfacial properties of CrX2N4 (X = C, Si) based field‐effect transistors (FETs) with different metal (Ag, Au, Cu, Ni, Pd, Pt, Ti, and graphene) electrodes by using electronic structure calculations and quantum transport simulations. It is highlighted that the stronger interlayer coupling allows CrC2N4 to form an n‐type Ohmic contact with Ti electrode in the vertical direction. Furthermore, the absence of tunneling barrier at the CrC2N4–Ti interface greatly improves the electron injection efficiency. On the other hand, the studied metals form Schottky contact with CrC2N4 at the lateral interface due to Fermi level pinning (FLP) effects. Surprisingly, the strong FLP effects restrict the Schottky barrier heights of CrSi2N4‐metal contacts to a narrow range. Where Ag, Au, Ni, Pd, Pt, Ti electrodes and Ag, Ti electrodes form ideal ohmic contact with CrSi2N4 in the vertical and lateral directions, respectively, while the other metals form quasi‐ohmic contact. Ti exhibits the highest contact performance as the electrode in both CrC2N4 and CrSi2N4 based FETs. The findings may provide fundamental understanding for designing high‐performance and energy‐efficient FETs based on CrX2N4. [ABSTRACT FROM AUTHOR]

Because of their unique mechanical and electrical properties, zinc oxide (ZnO) nanowires are used widely in microscopic and nanoscopic devices and structures, but characterizing them remains challenging. In this paper, two pick-up strategies are proposed for characterizing the electrical properties of ZnO nanowires using SEM equipped with a nanomanipulator. To pick up nanowires efficiently, direct sampling is compared with electrification fusing, and experiments show that direct sampling is more stable while electrification fusing is more efficient. ZnO nanowires have cut-off properties, and good Schottky contact with the tungsten probes was established. In piezoelectric experiments, the maximum piezoelectric voltage generated by an individual ZnO nanowire was 0.07 V, and its impedance decreased with increasing input signal frequency until it became stable. This work offers a technical reference for the pick-up and construction of nanomaterials and nanogeneration technology. HIGHLIGHTS: • Two nanowire pick-up strategies are proposed, and their advantages and disadvantages are analyzed quantitatively in terms of pick-up success rate. • The applicabilities of the two pick-up strategies are determined. The first strategy is highly versatile because it does not damage the nanowires, so it is generally used to characterize the electrical or mechanical-electrical properties of nanowires. The second strategy is strong in adsorption, but because it involves fusing the nanowires, it has greater impact on the contact resistance at the contact point, so it is generally used to characterize the nanowire mechanical properties. • The electrical properties of ZnO nanowires were characterized using a nanomanipulator system installed in a SEM vacuum chamber. The results show that Schottky contact was established between the probe tips and ZnO nanowires, and the I–V curves exhibited typical back-to-back Schottky characteristics. Because of the piezoelectric effect, ZnO nanowires become micro-power generation devices. [ABSTRACT FROM AUTHOR]

Nonmagnetic semiconductor based magnetoresistance (MR) devices combining high performance and low cost have attracted a lot of attention. However, it has been a great challenge to separate the interface MR from the bulk MR in the devices composed of Schottky heterojunctions. In this paper, the MR effect of a silicon-based Schottky heterojunction device had been studied, and its mechanisms were investigated by separating the interface MR effects from the bulk MR effects through combining two-probe and four-probe methods. We find that the bulk MR value is significantly smaller than the total MR value in the avalanche breakdown region in the temperature range of 150 K to 300 K, indicating that the total MR effect mainly originates from the interface MR effect. Theoretical analysis shows that the bulk MR effect is a normal one due to the existence of the Lorentz force on the carriers, and the interface MR effect relates to the suppression of the local plasmas by applying magnetic fields, where the local plasmas form due to the avalanche breakdown in the Ag/SiO2/p-Si Schottky heterojunctions. The total MR effect at room temperature can be further enhanced by reducing the distance between electrodes, and the total MR reaches about 1847% under a magnetic field of 1 T and the MR sensitivity is as large as 118.5 T−1 under 0.1 T. [ABSTRACT FROM AUTHOR]

Schottky's Conjecture posits that the geometric field enhancement produced by a hybrid shape formed from a small perturbation on a larger base is the product of the individual field enhancement factors of the base and perturbation in isolation. This is a powerful concept with practical applications to understanding field emitter design and operation, as actual field emitters have complicated surface shapes with structure and, therefore, contributions to field enhancement, occurring simultaneously on many length scales. Recent studies of the Conjecture imply that the degree to which it accurately predicts a hybrid structure's total field enhancement depends on the degree of self-similarity between the base and perturbation shapes. To explore these aspects of the Conjecture, we have used the zero-potential surface produced by simple charge distributions to produce compound shapes with small perturbations on larger base structures. In the limit of small perturbation strength, these simple models adequately approximate idealized compound shapes, such a hemisphere-on-hemisphere geometry. Changing the base shape and the location of the perturbation allows us to selectively degrade the self-similarity present in the problem geometry. Proofs of the Schottky Conjecture in the limit of small perturbation strength will be provided, using these techniques, for hemisphere-on-hemisphere and half-cylinder-on-half-cylinder systems—the latter being the geometry considered by Schottky and for which the Conjecture was first proposed, but not proven. [ABSTRACT FROM AUTHOR]

Schottky's Conjecture (SC) posits that when a compound conductive structure is formed by placing a protrusion on top of an underlying base, the total field enhancement factor is the product of the field enhancement factors that would be produced by the base and protrusion in isolation. This is a powerful concept, which, in principle, allows separate treatment of the electrostatic effects of geometric features occurring at differing length scales. Recent work suggests that the degree to which the SC holds depends on the shape of the protrusion and base, and, in particular, on their relative sizes and their degree of self-similarity. Here, we use a Line Charge Model (LCM) to study the applicability of the SC to compound, quasiellipsoidal structures. The general features of compound structures produced by the LCM are discussed. The SC consistently overpredicted the computed field enhancement factor but was seen to provide reasonable estimates, correct to within a factor of 2 or better, when the protrusion was sufficiently small compared to the base; a dependence of the threshold protrusion height on the base radius was identified. This range of applicability of the SC is more restrictive than that previously reported in the literature, and potential causes of this are discussed. [ABSTRACT FROM AUTHOR]

The monitoring of solar ultraviolet radiation from a space platform is now considered essential for a wide range of fields including solar physics, atmospheric science and astrobiology. 4H-Silicon Carbide (4H-SiC) is a superior alternative to conventional materials like silicon for the fabrication of UV detectors for adverse space conditions due to its inherent radiation hardness and visible-blind nature. This paper describes the space qualification and deployment of indigenously developed Pd/4H-SiC Schottky UV detectors in a low-earth orbit (LEO) and their on-board performance. Two SiC UV detectors were flown as a rad-hard sun detection sensor in the nanosatellite INS-2TD. The sensor has carried out solar UV flux observations continuously since its launch in February 2022 and the data gathered during the first seven months of flight is discussed in this paper. [ABSTRACT FROM AUTHOR]

A graphene–silicon Schottky junction (GSJ), which has potentials of large-scale manufacturing and integration, can bring new opportunities to Schottky solar cells for photovoltaic (PV) power conversion. However, the essential power conversion limitation for these devices lies in a small open-circuit voltage ( V o c ), which depends on the Schottky barrier height. In this study, we introduce an electromechanical method based on a flexoelectric effect to enhance the PV efficiency in GSJ. By atomic force microscope (AFM) tip-based indentation and in situ current measurement, the current–voltage (I–V) responses under a flexoelectric strain gradient are obtained. The V o c is observed to increase for up to 20%, leading to an evident improvement of the power conversion efficiency. Our studies suggest that the strain gradient may offer unprecedented opportunities for the development of GSJ-based flexo-photovoltaic applications. [ABSTRACT FROM AUTHOR]

[Display omitted] Heterogeneous catalysis composed of plasmonic metal and semiconductor has been utilized to tune local surface electron density in MOA (Molecular oxygen activation). However, there is a severe antagonistic effect between Schottky junction carriers and SPR (Surface Plasmon Resonance) induced hot carriers transfer routers when metal and semiconductor are both excited to dramatically reduce carriers separation efficiency. Hence, a highly effective photocatalytic antifoulant obtained by V-CN (carbon nitride with nitrogen vacancies) in-situ loading Cu 2 O and Ag nanoparticles (Cu 2 O/Ag/V-CN) was introduced to promote MOA to assist the metal ions sterilization. The DFT calculations (Density Functional Theory) and FEM calculations (Finite Element Method) intuitively proved the photocatalytic antifoulant belonged to a ternary Z-scheme heterojunction and could visibly weaken the antagonistic effect of hot carriers and Schottky carriers transport routes. The delocalized electron structure caused by V-CN and the effective electron mediator of Ag were the key to the formation of Z-scheme interfacial heterojunctions. These conclusions were also supported by experimental data, like more ∙O 2 – production capacity, efficient carriers separation, and higher carriers lifetime (27% higher than Cu 2 O and Cu 2 O/V-CN) as well as the weakened Cu 2 O photocorrosion tendency (Cu 2 O turning into CuO). Additionally, except for increasing nearly-three times adsorption energy of O 2 for rapid activation, Cu 2 O/Ag/V-CN with abundant nitrogen vacancies can more significantly slow metal ions release (less about 97% to pure Cu 2 O and at least 22% higher than reported systems), which can observably save the amount of catalyst and heavy metals content. Therefore, Cu 2 O/Ag/V-CN has great potential for practical antifouling applications. [ABSTRACT FROM AUTHOR]

A physical model and a mathematical approach were developed to describe ponderomotive acceleration a body pushed by plasma column of high-current arc in a railgun. In contrast to the previously published studies, the arc plasma generation was considered by taking into account kinetics of heavy particle fluxes in a non-equilibrium layer near the vaporizating (ablating) rails and the phenomena of heat and mass transfer and electric sheath at rail surfaces. The self-consistent numerical analysis has been conducted for a wide range of arc currents (up to 2MA). It has been shown that the electron temperature was determined mainly by the Joule energy dissipation supporting high degree of ionization. It has been determined that the arc voltage is about 102 V. The rails temperatures are relatively low (~ 3000 K) and therefore, the electron flux emitted from the cathode manly due to thermionic emission enhanced by Schottky effect is lower than the flux of ions from the plasma, which supported the current continuity at the cathode region. The calculated velocity vs of the plasma-solid body increased with the arc current (I) showing tendency to saturation. In range of I = 0.5–2 MA the vs slightly increased from 5 × 105 to 10 × 105 cm/s when the rail length increased from 1 to 3 m respectively. The dependence of the velocity on the arc current and the calculated plasma parameters are in range of those values observed experimentally. The nature of the velocity with arc current saturation is explained by presence of the dynamic pressure resulting in predicted velocity dependence on the arc current as 4-th root. [ABSTRACT FROM AUTHOR]

Carbon nanotubes (CNTs) are promising materials for gas sensing because of their large specific area and high sensitivity to charge differentiation. In CNT-based field-effect transistors (FETs) for gas sensing, both CNT potential modulation in the channels and Schottky barrier height modulation at the CNT/metal electrode contact influence the current properties. However, researchers have not used Schottky barrier height modulation for gas detection. To investigate and compare the effects of Schottky barrier height modulation and CNT channel potential modulation on NO2 gas exposure, we fabricated ambipolar CNT FETs by the dielectrophoretic assembly. We exposed CNT FET gas sensors to N2 gas containing 100-ppb NO2 and observed two different responses in the electric properties: a steady current shift in the positive direction in the hole-conduction region because of the channel potential modulation, and an abrupt decrease in transconductance in the electron-conduction region because of the Schottky barrier modulation. The CNT channels and CNT/metal contact both contributed to the sensor response, and the modulation rate of the Schottky barrier was higher than that of the CNT potential shift in the channel. [ABSTRACT FROM AUTHOR]

• NiS-decorated S-doped g-C 3 N 4 (NiS/SCN) degraded 96.2 % of norfloxacin after 90 min visible illumination. • Doping g-C 3 N 4 with sulfur reduces the band gap and thus broadens the response range to visible light. • The degradation pathway of norfloxacin over NiS/SCN was proposed as a schottky junction. • The trapping investigation exhibited that the •O 2 − and h + played dominant roles, which validated the proposed mechanism. • The NiS/SCN hybrid photocatalyst has an excellent steadiness. As a result of industrial expansion and ill-considered exploitation of resources, serious environmental issues have recently emerged that have led to damage to the ecosystem. In particular, antibiotics, such as norfloxacin (NOR) have emerged as highly hazardous contaminants resulting from the increased use of these drugs worldwide. Photocatalysis-based degradation using heterojunctions has become almost the only way to permanently and eco-friendly degrade these pollutants. Herein, noble metal-free nanohybrids composed of S-doped g-C 3 N 4 grafted by NiS (denoted as NiS/SCN) have been fabricated via hydrothermal and one-step polymerization (at 550 °C) procedures. The photocatalytic activity of 3 %NiS/SCN photocatalyst was almost 6- and 20-times as high as SCN and NiS, respectively, achieving 96.2 % NOR degradation within 90 min. The recommended photocarriers transfer pathway was suggested and supported experimentally. Considerably, loading a small amount of NiS cocatalyst over S-doped g-C 3 N 4 boosted performance in addition to efficient reusability. This increased photocatalytic activity can be attributed to the fact that doping g-C 3 N 4 with sulfur can reduce the bandgap and thus broaden the response range to visible-light, and the effective effect of Schottky junction can significantly improve the separation rate of electron-hole pairs. Accordingly, the constructed NiS/SCN nanocomposites are potential candidates for photocatalysis processes, particularly visible-light-induced degradation of organic pollutants. [Display omitted] [ABSTRACT FROM AUTHOR]

Computing inspired by the human brain requires a massive parallel architecture of low-power consuming elements of which the internal state can be changed. SrTiO3 is a complex oxide that offers rich electronic properties; here, Schottky contacts on Nb-doped SrTiO3 are demonstrated as memristive elements for neuromorphic computing. The electric field at the Schottky interface alters the conductivity of these devices in an analog fashion, which is important for mimicking synaptic plasticity. Promising power consumption and endurance characteristics are observed. The resistance states are shown to emulate the forgetting process of the brain. A charge trapping model is proposed to explain the switching behavior. [ABSTRACT FROM AUTHOR]

Computing inspired by the human brain requires a massive parallel architecture of low-power consuming elements of which the internal state can be changed. SrTiO3 is a complex oxide that offers rich electronic properties; here, Schottky contacts on Nb-doped SrTiO3 are demonstrated as memristive elements for neuromorphic computing. The electric field at the Schottky interface alters the conductivity of these devices in an analog fashion, which is important for mimicking synaptic plasticity. Promising power consumption and endurance characteristics are observed. The resistance states are shown to emulate the forgetting process of the brain. A charge trapping model is proposed to explain the switching behavior. [ABSTRACT FROM AUTHOR]

We investigated the influence of space charge region (SCR) on the electrical properties of Pb0.95La0.05Zr0.54Ti0.46O3 (PLZT) thin film based capacitor structures. The metal/PLZT/Pt capacitors were prepared by using metal electrodes (Pt, Au, Al) of varying work function as top electrodes, and Pt as a bottom electrode. The SCR formed at the top interface between the PLZT film and the metal differs from each other in three capacitor structures. The results obtained from the hysteresis, dielectric, and leakage current measurements were analyzed to understand the variation in the electrical properties of the capacitors arising from the different SCRs formed at the interfaces. Among the three, the Pt/PLZT/Pt capacitor showed highest polarization and permittivity, and lowest FCC and coercive field. The Al/PLZT/Pt capacitor showed lowest polarization and permittivity, but higher coercive field and FCC. The leakage current increased with a decrease in work function of the top electrode. The Schottky conduction mechanism was found to be dominant in all the three capacitors. Both the photovoltaic parameters (short circuit photocurrent denisty and open circuit photovoltage) increased with the increase in work function of the top electrodes. These studies suggest the existence of wider SCR and higher space charge field at the top interface in the case of capacitor designed with an Al (or Au) top electrode as compared to the capacitor designed with a Pt top electrode. [ABSTRACT FROM AUTHOR]

A research of total ionizing dose and annealing effects on Schottky type p-GaN gate Al0.2Ga0.8N/GaN high electron mobility transistors (HEMTs) has been carried out. Devices with breakdown voltages of 100V/200V/650V were irradiated under Co-60 X-rays. Radiation doses reach to a total amount of 500 krad (Si) with dose rate of 50 rad(Si)/s under gate biases of ${V}_{GS}=0\text{V}$ /+3V/+5V. Negative threshold voltage shifts were observed, especially under positive gate biases. It is found out that the threshold voltage shifts are due to the accumulation of positive charges (holes) trapped in the interface of p-GaN/AlGaN. Therefore, the shift amount is proportional to the gate bias and the radiation amount, while not related to the breakdown voltage. After the total ionizing dose experiments, both high temperature and room temperature annealing processes were taken. During the annealing processes, the shifted threshold voltage recovered, and high temperature accelerated the recovery process. Experiment results indicate that the total ionizing dose effect is recoverable. [ABSTRACT FROM AUTHOR]