Interfacial Charge Polarization Research Articles

Effective charge separation in CdS@PANI heterostructure for ultrafast visible light-driven photocatalytic reduction of uranium(VI)

The efficient treatment of uranium-containing wastewater provides guarantee for sustainable development of nuclear energy. In this work, a heterogeneous interface structure for photocatalytic reduction of U(VI) was proposed by in-situ decoration of cadmium sulfide (CdS) nanoparticles on polyaniline (PANI) nanorods. The strong coupling between CdS and PANI precisely modulated the interface electronic structure, which promoted the photogenerated charge separation. Multiple spectroscopic characterizations revealed that the interfacial charge polarization with the electrons gathering at the CdS surface and the holes gathering at the PANI, facilitating the performance of photocatalytic reduction of U(VI) under visible light irradiation. The optimal CdS@PANI-10 shows ultrafast U(VI) reduction with efficiency of over 96 % in 5 min. Moreover, the photocatalytic reduction of U(VI) over CdS@PANI-10 can also be activated by direct natural sunlight irradiation. The improvement of catalytic activity of CdS@PANI nanocomposite is due to faster charge separation and migration at the interface between CdS and PANI, as well as the formation of Type-II heterojunction, which was also beneficial for suppressing the CdS photocorrosion. This work introduces a potential strategy to design advanced photocatalysts with efficient electrons and holes separation toward practical application in uranyl ion conversion.

Influence of image forces on charge-dipole interaction in two-layered systems.

Interaction between a fixed point electric charge Q and a freely rotating point electric dipole with the magnitude P pinned near a plane interface between two dispersionless insulators with different dielectric permittivities ɛ1 and ɛ2 has been considered. It was shown that, as a result of this interaction and the interaction of the dipole with the polarization charges induced at the interface by the charge Q and the dipole itself, there arise regions where the dipole can possess either one or two equilibrium orientations. The spatial distributions of the electrostatic dipole energy Wtotal under the combined action of the charge Q and the induced interface polarization charges, as well as the equilibrium dipole orientations (orientation maps), the boundaries between the regions with different numbers of dipole orientations, and their evolution with the variation of problem parameters (the charge and dipole magnitudes, the mismatch between ɛ1 and ɛ2, and the charge-interface distance) were calculated. It was shown that there can emerge local minima of Wtotal, which may play the role of traps for dipoles (in particular, excitons in layered structures), and the corresponding requirements for the problem parameters were found. Most results were obtained in analytical form. The model can be applied to various physical systems, for instance, polar molecules, excitons, and trions in layered structures.

Engineering Spin Polarization of the Surface-Adsorbed Fe Atom by Intercalating a Transition Metal Atom into the MoS2 Bilayer for Enhanced Nitrogen Reduction.

The precise control of spin states in transition metal (TM)-based single-atom catalysts (SACs) is crucial for advancing the functionality of electrocatalysts, yet it presents significant scientific challenges. Using density functional theory (DFT) calculations, we propose a novel mechanism to precisely modulate the spin state of the surface-adsorbed Fe atom on the MoS2 bilayer. This is achieved by strategically intercalating a TM atom into the interlayer space of the MoS2 bilayer. Our results show that these strategically intercalated TM atoms can induce a substantial interfacial charge polarization, thereby effectively controlling the charge transfer and spin polarization on the surface Fe site. In particular, by varying the identity of the intercalated TM atoms and their vacancy filling site, a continuous modulation of the spin states of the surface Fe site from low to medium to high can be achieved, which can be accurately described using descriptors composed of readily accessible intrinsic properties of materials. Using the electrochemical dinitrogen reduction reaction (eNRR) as a prototypical reaction, we discovered a universal volcano-like relation between the tuned spin and the catalytic activity of Fe-based SACs. This finding contrasts with the linear scaling relationships commonly seen in traditional studies and offers a robust new approach to modulating the activity of SACs through interfacial engineering.

A high performance piezoelectric hetero-junction based on the configuration reform on interfacial potential barrier

In this paper, the barrier region of a mixed hetero-junction consisting of a p-type Si and an n-type ZnO was fully opened by abandoning the depletion layer approximation in advance. The barrier configuration was reconstructed by the artificial potential barrier based on a new fully coupled model in which the interaction between physical fields and charge carriers was taken into account. Then, we put forward an interesting design idea of elevating the mechanical regulation performance of a PN junction by manufacturing it with a third-generation piezoelectric semiconductor and a narrow bandgap semiconductor. It is through the deformation of the third-generation piezoelectric semiconductor on one side under mechanical loadings to excite polarization charges at the PN interface such that the movement of charge carriers in the narrow bandgap semiconductor on the other side is able to be tuned by the interface polarization charges. Besides, it is found a specific current-stress characteristic for such a mixed hetero-junction, which will present three stages, i.e., rising stage, platform stage and falling stage. The rising stage is caused by the improving recombination rate, which can be used as a high sensitivity stress sensor (output current improved by more than 10 times in a small stress). Oppositely, the falling stage is caused by the weakened recombination rate due to carrier type-inversion, which can be used to determine overload (output current reduced dramatically when the stress increased to a specific value). Finally, the platform stage is caused by the competition of the above two cases. At this stage, the device operates very stable and can resist the external perturbation. Obviously, the study possesses referential significance to the design and mechanical tuning on performance of piezotronic devices.

Electrokinetic, electrochemical, and electrostatic surface potentials of the pristine water liquid-vapor interface.

Although conceptually simple, the air-water interface displays rich behavior and is subject to intense experimental and theoretical investigations. Different definitions of the electrostatic surface potential as well as different calculation methods, each relevant for distinct experimental scenarios, lead to widely varying potential magnitudes and sometimes even different signs. Based on quantum-chemical density-functional-theory molecular dynamics (DFT-MD) simulations, different surface potentials are evaluated and compared to force-field (FF) MD simulations. As well explained in the literature, the laterally averaged electrostatic surface potential, accessible to electron holography, is dominated by the trace of the water molecular quadrupole moment, and using DFT-MD amounts to +4.35V inside the water phase, very different from results obtained with FF water models which yield negative values of the order of -0.4 to -0.6V. Thus, when predicting potentials within water molecules, as relevant for photoelectron spectroscopy and non-linear interface-specific spectroscopy, DFT simulations should be used. The electrochemical surface potential, relevant for ion transfer reactions and ion surface adsorption, is much smaller, less than 200 mV in magnitude, and depends specifically on the ion radius. Charge transfer between interfacial water molecules leads to a sizable surface potential as well. However, when probing electrokinetics by explicitly applying a lateral electric field in DFT-MD simulations, the electrokinetic ζ-potential turns out to be negligible, in agreement with predictions using continuous hydrodynamic models. Thus, interfacial polarization charges from intermolecular charge transfer do not lead to significant electrokinetic mobility at the pristine vapor-liquid water interface, even assuming these transfer charges are mobile in an external electric field.

Defect and interface control on graphitic carbon nitrides/upconversion nanocrystals for enhanced solar hydrogen production

<p indent="0mm">The effective utilization of solar energy for hydrogen production requires an abundant supply of thermodynamically active photo-electrons; however, the photocatalysts are generally impeded by insufficient light absorption and fast photocarrier recombination. Here, we report a multiple-regulated strategy to capture photons and boost photocarrier dynamics by developing a broadband photocatalyst composed of defect engineered g-C₃N₄ (DCN) and upconversion NaYF₄:Yb³⁺,Tm³⁺ (NYF) nanocrystals. Through a precise defect engineering, the S dopants and C vacancies jointly render DCN with defect states to effectively extend the visible light absorption to <sc>590 nm</sc> and boost photocarrier separation via a moderate electron-trapping ability, thus facilitating the subsequent re-absorption and utilization of upconverted photons/electrons. Importantly, we found a promoted interfacial charge polarization between DCN and NYF has also been achieved mainly due to Y-N interaction, which further favors the upconverted excited energy transfer from NYF onto DCN as verified both theoretically and experimentally. With a 3D architecture, the NYF@DCN catalyst exhibits a superior solar H₂ evolution rate among the reported upconversion-based system, which is 19.3 and 1.5 fold higher than bulk material and DCN, respectively. This work provides an innovative strategy to boost solar utilization by using defect engineering and building up interaction between hetero-materials.

Electronic Metal-Support Interaction Triggering Interfacial Charge Polarization over CuPd/N-Doped-C Nanohybrids Drives Selectively Electrocatalytic Conversion of Nitrate to Ammonia.

Selective electrocatalytic nitrate-to-ammonia conversion holds significant potential in treatment of nitrate wastewater and simultaneously produces high-value-added ammonia. However, today's development of nitrate-to-ammonia technology remains hindered by the lack of electrocatalysts with high activity and selectivity. In this work, metal-organic framework-derived CuPd bimetallic nanoparticles/nitrogen-doped carbon (CuPd/CN) hybrid nanoarrays for efficient ammonia electrosynthesis from nitrate are designed and synthesized. Systematic characterization reveals that the electronic metal-support interaction between the CuPd nanoparticles and N-doped nanocarbon matrix could trigger interfacial charge polarization over the CuPd/CN composite and make Cu sites electron deficient, which is conducive to the adsorption of nitrate ions. Moreover, the Pd atom sites separate by Cu atoms and could catalyze the dissociation of H2 O molecules to form adsorbed H species, which evolves into hydrogen radicals and behaves as the dominant reactive species in accelerating nitrate-to-ammonia electrocatalysis. These advantages endow the CuPd/CN nanoarrays with high faradaic efficiency (96.16%), selectivity (92.08%) as well as excellent catalytic stability for electroreduction of nitrate to ammonia.

Hollow-structured CoP nanotubes wrapped by N-doped carbon layer with interfacial charges polarization for efficiently boosting oxygen reduction/evolution reactions

• 1D hollow CoP nanotubes wrapped by NCL are used as efficient catalysts for ORR/OER. • The well-formed 1D hollow structure can exposure more active sites for mass transfer. • CoP/CoOOH heterostructure on CoP-HNTs surface as the main active-species for OER. • Charge redistribution at the CoP/NCL interface promotes both ORR and OER processes. • Graphene layer protects CoP-HNTs@NCL from aggregation and corrosion during ORR/OER. Structure engineering for electrocatalysts via interfacial charge redistribution plays a vital role in governing the electrocatalytic activity for both oxygen reduction and evolution reactions (ORR/OER). Herein, a hierarchical nanostructure consisting of one-dimension (1D) hollow CoP nanotubes wrapped by nitrogen-doped carbon layer (CoP-HNTs@NCL) is designed through a simple hydrothermal-phosphorization-annealing strategy. Morphology of CoP-HNTs@NCL-0.4 (mass ratio of GO to CoP is 0.4) shows that the exterior surface of hollow CoP-HNTs is firmly coated by NCL with a layer thickness of 5-8 nm. ΔE (E j10 (1.58 V, OER)-E 1/2 (0.91 V, ORR)) of CoP-HNTs@NCL-0.4 is as low as 0.67 V for ORR/OER, which outperforms commercial Pt/C and RuO 2 and ranks the top of nonprecious-metal catalysts. Excellent activity and stability of CoP-HNTs@NCL-0.4 for ORR/OER benefit from synergistic effects between CoP and NCL, enhanced mass transfer via 1D hollow structure, and abundant active sites exposed on the interior/exterior surfaces of nanotube wall. Density functional theory calculations confirm that strong coupling interactions lead to interfacial charge polarization to remarkably promote the ORR/OER activities. This study highlights the functions of 1D hollow structure and interface effects in oxygen electrocatalysis, and opens a new avenue for interface construction by synergistically integrating favorable thermodynamics with efficient kinetics through modification of electronic structure.

Controlling the Interfacial Charge Polarization of MOF-Derived 0D-2D vdW Architectures as a Unique Strategy for Bifunctional Oxygen Electrocatalysis.

The design of alternative earth-abundant van der Waals (vdW) nanoheterostructures for bifunctional oxygen evolution/reduction (OER/ORR) electrocatalysis is of paramount importance to fabricate energy-related devices. Herein, we report a simple metal-organic framework (MOF)-derived synthetic strategy to fabricate low-dimensional (LD) nanohybrids formed by zero-dimensional (0D) ZrO2 nanoparticles (NPs) and heteroatom-doped two-dimensional (2D) carbon nanostructures. The 2D platforms controlled the electronic structures of interfacial Zr atoms, thus producing optimized electron polarization for boron and nitrogen-doped carbon (BCN)/ZrO2 nanohybrids. X-ray photoelectron spectroscopy (XPS) and theoretical studies revealed the key role of the synergistic couple effect of boron (B) and nitrogen (N) in interfacial electronic polarization. The BCN/ZrO2 nanohybrid showed excellent bifunctional electrocatalytic activity, delivering an overpotential (η10) of 301 mV to reach a current density of 10 mA-cm-2 for the OER process and a half-wave potential (E1/2) of 0.85 V vs reversible hydrogen electrode (RHE) for the ORR process, which are comparable to the state-of-the-art LD nanohybrids. Furthermore, BCN/ZrO2 also showed competitive performances for water-splitting and zinc-air battery devices. This work establishes a new route to fabricate highly efficient multifunctional electrocatalysts by tuning the electronic polarization properties of 0D-2D electrochemical interfaces.

PtCu thickness-modulated interfacial charge transfer and surface reactivity in stacked graphene/Pd@PtCu heterostructures for highly efficient visible-light reduction of CO2 to CH4

Photocatalytic conversion of CO2 to chemical feedstocks represents an intriguing approach to address the energy and environmental crisis, but faces low conversion efficiencies resulted from unsatisfied light absorption, charge recombination and surface reactivity of traditional semiconductor photocatalysts. Herein, we report stacked graphene/Pd@PtCu nanostructures with atomically thin PtCu shell to overcome above challenges and realize high-efficient CO2-to-CH4 photoreduction. The smart design begins with the excitation of Ru complex with broad visible absorption, which is followed by the smooth movement of photoelectrons via the graphene→Pd→PtCu pathway, and then the highly selective CO2 reduction on the PtCu surface. As the PtCu thickness decreases, the strengthened Pd–PtCu interfacial charge polarization contributes to improved charge separation/migration. Meanwhile, CO2 adsorption on the PtCu surface is ameliorated owing to increased electron accumulation and compressive strain. This work provides a new design for boosting the photocatalytic performance by cooperative surface and interfacial modulations.

Enhanced domain wall conductivity in photosensitive ferroelectrics Sn2P2S6 with full-visible-spectrum absorption

Recent optical stimulation suggests a vital non-contact pathway to manipulate both macroscopic and microscopic ferroelectric properties and paves the foundation for optoelectronics devices. However, up to date, most optical-related manipulation of ferroelectric properties is restricted due to their intrinsic bandgap and limited visible light spectrum absorption. Here, we reveal non-oxide Sn2P2S6 single crystal possesses full-visible-spectrum absorption (from 300 to 800 nm) with a unique disproportionation mechanism of photoexcited Sn ions and Urbach tail, which is not contradicting to the intrinsic band gap. Interestingly, we observed the existence of conductive domain walls (c-DW) and the light illumination induced significant enhancement of the domain wall conductivity caused by such disproportionation reaction. In addition, the domains separated by c-DW also exhibited noticeable electrical conductivity difference in the presence of optical illumination owing to the interfacial polarization charge with opposite signs. The result provides a novel opportunity for understanding the electrical conductivity behavior of the domains and domain walls in ferroelectrics with full-visible-spectrum absorption and achieving greatly enhanced performances for optoelectronics.

Domain-wall induced giant tunneling electroresistance effect in two-dimensional Graphene/In2Se3 ferroelectric tunnel junctions

Ferroelectric tunnel junctions (FTJs) are very promising as a new type of nonvolatile memory devices due to the tunneling electroresistance (TER) effect. In recent years, with the rise of two-dimensional (2D) materials, 2D ferroelectrics and their application in FTJs have attracted intensive attention, with the advantage of greatly reducing the FTJ based memory device sizes, as demanded by the ongoing device minituriazation in modern electronic circuits. However, all present schemes for realizing giant TER ratio with 2D FTJs are based on the polarization reversal of the whole ferroelectric layer upon an electrical field. In this work, we explore the quantum transport properties of the 2D FTJs with the partial reversal of polarization, namely, the formation of domain walls (DWs) by constructing two kinds of FTJs. One is in a uniform-polarization state and the other one is a state with domain walls. Structural relaxation confirms the stability of the domain-wall state. By quantum transport calculation, we obtain a TER ratio as high as 2.75 × 10 4 % . Further analysis of the electronic structure shows that there is charge accumulation or charge depletion at the two DWs. Such asymmetric interface polarization charges result in a built-in electrical field and thus affect the distribution of the effective potential along the transport direction. This leads to partial metal-insulator transition around the DWs and finally the giant TER ratio. Our results indicate that DWs may greatly affect the quantum transport and provide a new mechanism for realizing giant TER effect in 2D FTJs.

Comparison between lead free BaTio3/PDMS and doped - PZT/PDMS composite on ferroelectric characteristics

Composites of BaTiO3 (BT) and doped-PZT (d-PZT) micro-particles randomly dispersed in a PDMS matrix were prepared by a molding process. The morpho-structural characterization, performed by SEM and XRD, showed ceramic micro-grains of cubic BT and orthorhombic d-PZT, randomly dispersed in the PDMS matrix. Polarization (P) as a function of the applied field (E) was measured for composite samples, as well as for polymer samples. Hysteresis loops typical for a dielectric material were obtained, but also atypical ones, especially for higher fraction of polymer in composite, lower fields and shorter measuring periods, as a result of the dielectric relaxation in polymer and the presence of interfacial polarization charges at the contact between polymer and ferroelectric. All these composites show very low polarizations (less than 0.2 µC/cm2 and 0.05 µC/cm2 the maximum and remnant polarization, respectively), caused by the very low dielectric constant of the polymer (less than 10), which drastically reduces, up to 100 times, the electric field effectively applied to the ferroelectric. Weak pyroelectric response was recorded on BT/PDMS, but a typical behavior of a pyroelectric detector was observed. A figure of merit of the material which exceeds 10-4 m 2 /C was estimated.

Nanoscale electromagnetic boundary conditions based on Maxwell’s equations

The electromagnetic boundary conditions have great important applications in many physical branchs. Here, the nanoscale electromagnetic boundary conditions are derived by using the integral Maxwell’s equations through constructing the dielectric transition layer across the interface between the two materials. The two interface response functions are obtained to reflect the electromagnetic field response characteristics of the interface. Based on the Maxwell’s equations, the physical meanings of the interface response functions are given as the position of the equivalent interfacial polarization charge and the gradient position of interfacial polarization current density, respectively. The influence of the dielectric constant of the medium, the transition line shape of the electric field and the frequency on the interface response functions are analyzed. When the material scale is large, the interface response function can be ignored, and the nanoscale electromagnetic boundary conditions degenerate to the classical boundary conditions given by the abrupt junction. On this basis, the interface electric dipole moment, the equivalent interfacial polarization charge area density, the equivalent interfacial polarization current density and the equivalent interfacial magnetic current density are introduced, leading to three forms of nanoscale electromagnetic boundary conditions. The results provide a clear physical picture and necessary theoretical basis for nanoscale electromagnetism and interface optics.

Tailorable Dielectric Performance of Niobium‐Modified Poly(hydridomethylsiloxane) Precursor‐Derived Ceramic Nanocomposites

The low‐frequency dielectric behavior of in situ crystallized and stabilized nanocrystalline t‐NbO2 in amorphous silicon oxycarbide (SiOC) ceramic nanocomposites derived from niobium‐modified poly(hydridomethylsiloxane) (PHMS) is reported. Commercially available PHMS is modified using Nb(OC2H5)5 via chemical and mechanical mixing route. It is observed that the synthesis route and heat‐treatment temperatures significantly affect the crystallization of the ceramic phases, where c‐NbC and t‐NbO2 in amorphous SiOC are formed through chemical and mechanical modification route, respectively. The variation in dielectric permittivity and loss at room temperature with respect to ceramic phases is comprehensively investigated. In contrast to amorphous SiOC ceramics derived from PHMS (ε′ = 100.0 at 1 Hz), t‐NbO2 in amorphous SiOC ceramic exhibits colossal dielectric permittivity (ε′ = 5.0 × 105 at 1 Hz) with low loss (tan δ &lt; 3.0). This is attributed to an interfacial charge polarization and in situ growth of insulator/semiconductor/insulator ceramic phases in amorphous SiOC ceramic nanocomposites.

Effect of Radial Moisture Distribution on Frequency Domain Dielectric Response of Oil-Polymer Insulation Bushing.

In order to realize the diagnosis of water distribution, this paper analyzes the interface polarization and macroscopic space charge polarization mechanism when the water distribution is non-uniform. The experimental results of this paper and bushing show that when the moisture distribution is non-uniform, there is a significant loss peak in the tanδ-f curve. The loss peak shifts to higher frequencies as the non-uniformity coefficient increases. There are common intersection points between multiple tanδ-f curves. Further, this paper realizes the diagnosis of the location of moisture distribution through Frequency Domain Spectroscopy (FDS) testing of different voltages and different wiring methods based on the macroscopic space charge polarization. In the single-cycle FDS test, when the positive electrode is first added to the area with higher moisture content, the amplitude of the tanδ-f curve is smaller. The tanδ-f curves under different wiring methods constitute a “ring-shaped” loss peak. As the voltage increases, the peak value of the loss peak shifts to the lower frequency band. As the temperature increases, the peak value of the loss peak shifts to higher frequencies. Based on the above rules and mechanism analysis, this research provides a new solution for the evaluation of moisture content of oil-immersed polymers equipment.

One-step In-situ Synthesis of Vacancy-rich CoFe2O4@Defective Graphene Hybrids as Bifunctional Oxygen Electrocatalysts for Rechargeable Zn-Air Batteries

Developing efficient catalysts toward both oxygen reduction reaction(ORR) and oxygen evolution reaction(OER) is the core task for rechargeable metal-air batteries. Although integration of two active components should be an effective method to produce the bifunctional catalysts in principle, traditional techniques still can not attain fine tunable surface structure during material-hybridization process. Herein, we present a facile short-time in-situ argon(Ar) plasma strategy to fabricate a high-performance bifunctional hybrid catalyst of vacancy-rich CoFe2O4 synergized with defective graphene(r-CoFe2O4@DG). Reflected by the low voltage gap of 0.79 V in two half-reaction measurements, the striking capability to catalyze ORR/OER endows it excellent and durable performance in rechargeable Zn-air batteries, with a maximum power density of 155.2 mW/cm2 and robust stability(up to 60 h). Further experimental and theoretical studies validate its remarkable bifunctional energetics root from plasma-induced surface vacancy defects and interfacial charge polarization between DG and CoFe2O4. This work offers more opportunities for reliable clean energy systems by rational interfacial and defect engineering on catalyst design.

Research on epoxy-based nanocomposites with high energy density and charge-discharge efficiency filled with Ti02 nanofibers

Capacitor films with high energy density are critical to energy storage. However, the energy density of state-of-the-art commercial capacitor films are limited by their low dielectric permittivity. In this study, epoxy-based nanocomposite films are prepared by filling with Ti02 nanofibers. Results show that nanocomposite films have larger discharge energy density because of the significant increase in dielectric permittivity, which caused by the additional interface polarization and space charge polarization. And a superior charge-discharge efficiency is achieved in the composite films at the same time due to the low dielectric loss. In addition, the composites also keep a high breakdown strength because of the dispersion of the nanofibers. The discharge energy density of 5.19 J/cm3 with the efficiency of 80% is achieved at 470 MV/m in the nanocomposites containing 2wt% nanofibers. The excellent energy density and charge-discharge efficiency of epoxy-based nanocomposites offer a promising opportunity for future researches and industrial application.

Investigation of SiN x and AlN Passivation for AlGaN/GaN High-Electron-Mobility Transistors: Role of Interface Traps and Polarization Charges

In this work, we studied the mechanisms and switching properties of AlGaN/GaN high-electron-mobility-transistors (HEMTs) passivated by amorphous-SiN x and monocrystal-like AlN. The effects of interface traps and polarization charges on current collapse are investigated by TCAD simulations and experimental characterizations. Surface/interface deep levels can be compensated by both shallow donor-like traps (SiN x passivation) and polarization charges (AlN passivation) at passivation/heterostructure interface, but with different levels of effectiveness under fast switching conditions. SiN x -passivation introduces shallow donor-like trap states with short time constant that favors a fast emission of trapped electrons in the access region and suppressed current collapse, but nevertheless exhibits more severe time-dependent recovery of dynamic on-resistance. For AlN passivation, interface traps are compensated by the fixed positive polarization charges and the off-state depletion region (in the 2DEG channel) is formed predominantly by electric-field effect, leading to an immediate accumulation of high channel electron concentration after switching the HEMT devices back to on-state and instant response of drain current to gate and drain bias. The field plate structure is necessary in SiN x -passivated devices for both current collapse suppression and electric field alleviation. With AlN passivation, the field plate can be solely designed for achieving more uniform electric field distribution for gate reliability concern without the concern of current collapse.

Ohmic contact formation mechanisms of TiN film on 4H–SiC

The atomic structure, interfacial charge distribution, bonding nature, and interfacial electronic states of a 4H–SiC/TiN interface are systematically investigated to understand the Ohmic contact formation mechanisms of TiN to 4H–SiC. The experiment results clearly demonstrate that the well-arranged TiN (111)-oriented lattice planes are parallel to the (0001) SiC-oriented substrate, which is in line with the XRD results. In addition, the interface is coherent without any secondary phase layers, amorphous layers, or transition regions, which confirms the direct contact of TiN to SiC at the atomic scale, exhibiting a linear current–voltage relationship. Quantitatively, first-principle calculations reveal that the Schottky barrier height (SBH) is as low as 0.03 eV and that the band gap nearly vanishes at the interface, indicating an excellent Ohmic contact of TiN to 4H–SiC. Furthermore, the SBH is significantly reduced through the interfacial charge polarization effect and strong coupling of interfacial electronic states, enhancing the quantum electron transport. The present results provide insight into the complicated electronic effects of the Ohmic contact interface and indicate that TiN is a promising SiC Ohmic contact material for advanced next-generation power device applications.