Electron Tunneling Research Articles

Disentangling Electronic and Phononic Thermal Transport Across 2D Interfaces

Abstract Electrical and thermal transport at 2D interfaces is critical for semiconductor technology, yet their interplay remains unclear. We report a theoretical proposal to separate electronic and phononic contributions to thermal conductance at 2D interfaces with graphene, which is validated by non-equilibrium Green’s function calculations and molecular dynamics simulations for graphene-gold contacts. Our results reveal that while metal-graphene interfaces are transparent for both electrons and phonons, non-covalent graphene interfaces block electronic tunneling beyond two layers but not phonon transport. This suggests that the Wiedemann-Franz law can be experimentally tested by measuring transport across interfaces with varying graphene layers.

Enhanced performance of hafnia self-rectifying ferroelectric tunnel junctions at cryogenic temperatures

The advancement in high-performance computing technologies, including quantum and aerospace systems, necessitates components that operate efficiently at cryogenic temperatures. In this study, we demonstrate a hafnia-based ferroelectric tunnel junction (FTJ) that achieves a record-high tunneling electroresistance (TER) ratio of over 200,000 and decade-long retention characteristics. By introducing asymmetric oxygen vacancies through the strategic use of indium oxide (InOx) layer, we enhance the TER ratio without increasing off-current, addressing the longstanding issue of low on-current in hafnia-based FTJs. Unlike prior approaches that led to leakage currents, our method optimizes tunneling behavior by leveraging the differential oxygen dissociation energy between InOx and hafnium zirconium oxide (HZO). This results in asymmetric modulation of the tunnel barrier, enhancing electron tunneling in one polarization state while maintaining stability in the opposite state. Furthermore, we explore the intrinsic characteristics of the FTJ at cryogenic temperatures, where reduced thermal energy minimizes leakage currents and allows the maximization of device performance. These findings establish a new benchmark for TER in hafnia-based FTJs and provide valuable insights for the integration of these devices into advanced cryogenic memory systems.Graphical

Self‐Rectifying Switching Memory Based on HfOx/FeOx Semiconductor Heterostructure for Neuromorphic Computing

AbstractSneak‐path current is one of the biggest barriers for large‐scale passive memristor array integration. An ideal self‐rectifying resistance random access memory (SR‐RRAM) is a desirable solution but it has not been demonstrated today for optimizing comprehensive indexes for neuromorphic computing. The HfOx/FeOx semiconductor heterojunction SR‐RRAM with a robust self‐rectifying switching behavior featured by an average rectifying ratio (≈104), high resistance ratio (>106), high cycling endurance (>104 cycles), high computing precision (>6 bits) and synaptic plasticity such as paired‐pulse facilitation (PPF) and the spike‐timing‐dependent plasticity (STDP) for artificial intelligence recognition is developed using the unidirectional conductivity feature of p‐n junction. The electron hopping, tunneling, and blocking in this semiconductor heterojunction that is verified by the energy band mode based on UV photoelectron spectroscopy (UPS) technology and low‐energy inverse photoelectron spectroscopy (LEIPS) and in situ high resolution transmission electron microscopy (HR‐TEM) observation plays a dominant role in the self‐rectifying analog switching behaviors. This work provides energy‐band engineering for the large‐scale memristor array integration, representing a significant advancement in hardware for neuromorphic computing.

Ultrafast Cycloreversion of Thymine-Toluene [2 + 2] Cycloadducts by DNA Photolyase.

DNA photolyases use blue light and fully reduced flavin cofactor to repair UV-induced cyclobutane pyrimidine dimers (CPD) formed between two adjacent thymine bases in DNA. Thymine can form [2 + 2] cyclobutane adducts with its biological isosteres like toluene upon UV irradiation, resulting in chemically different analogues of CPD. Here, we investigated the cycloreversion reactions of two such adducts formed between thymine and toluene, T<>Tol, catalyzed by a class-I CPD photolyase. The photolyase can bind to the T<>Tol adducts efficiently and restore the constituent bases upon excitation. Using femtosecond spectroscopy, we systematically characterized all the elementary steps involved in the enzymatic cycloreversion of the T<>Tol adducts and comprehensively analyzed the key intermolecular electron-transfer (ET) reactions and cyclobutane bond splitting steps. The initial electron injection to the bound adducts happens primarily through a two-step electron hopping mechanism, unlike in CPD repair where direct electron tunneling is dominant. After electron injection and ultrafast first-bond splitting, the delicate competition between the second bond splitting and a futile back ET dictates the overall reaction quantum yields of the adducts, influenced by the stability of adduct intermediates and steric crowding around the constituent bases. The final electron return for the cycloreversion reactions adopts a different pathway compared to CPD repair. The photolyase utilizes its conserved photorepair mechanism and allows ET pathway flexibility to reverse the [2 + 2] cycloaddition reaction of non-natural analogues of CPD.

Characterization of Coulomb Interactions in Electron Transport Through a Single Hetero-Helicene Molecular Junction Using Scanning Tunneling Microscopy.

Characterization of the structural and electron transport properties of single chiral molecules provides critical insights into the interplay between their electronic structure and electrochemical environments, providing broader implications given the significance of molecular chirality in chiroptical applications and pharmaceutical sciences. Here, we examined the topographic and electronic features of a recently developed chiral molecule, B,N-embedded double hetero[7]helicene, at the edge of Cu(100)-supported NaCl thin film with scanning tunneling microscopy and spectroscopy. An electron transport energy gap of 3.2 eV is measured, which is significantly larger than the energy difference between the highest occupied and the lowest unoccupied molecular orbitals given by theoretical calculations or optical measurements. Through first-principles calculations, we demonstrated that this energy discrepancy results from the Coulomb interaction between the tunneling electron and the molecule's electrons. This occurs in electron transport processes when the molecule is well decoupled from the electrodes by the insulating decoupling layers, leading to a temporary ionization of the molecule during electron tunneling. Beyond revealing properties concerning a specific molecule, our findings underscore the key role of Coulomb interactions in modulating electron transport in molecular junctions, providing insights into the interpretation of scanning tunneling spectroscopy features of molecules decoupled by insulating layers.

Vibrational and Magnetic States of Point Defects in Bilayer MoSe2.

Defects in two-dimensional materials profoundly impact the physicochemical properties of the systems, whose characterization is highly desirable at the atomic scale. Here, using spectroscopic imaging scanning tunneling microscopy, we elucidate the vibrational and magnetic states of MoSe antisite and VMo vacancy with different charge states embedded in ultrathin MoSe2 bilayers supported on graphene substrate. Stringent vibronic states with multimode coupling are resolved on the defects. The spectral intensities are tunable with the electron tunneling rates and well-reproduced by theoretical modeling. Moreover, first-principles calculations suggest that the defects host a local magnetic moment of 2 μB in their neutral state, which is directly confirmed by our spin-flip inelastic electron tunneling spectroscopy. Our study deepens the understanding of defect properties and paves the way of defect-engineering material functionalities and spin-catalytic applications.

First principles electron transport in magnetoelectric SrRuO3/BaTiO3/SrTiO3/SrRuO3interfaces.

Recently, all-oxide ferroelectric tunnel junctions, with single or composite potential barriers based on SrRuO3/BaTiO3/SrTiO3(SRO/BTO/STO) perovskites, have drawn a particular interest for high density low power applications, due to their highly tunable transport properties and device scaling down possibility to atomic size. Here, using first principles calculations and the NEGFs formalism, we explore the electronic structure and tunneling transport properties in magnetoelectric SRO/BTO/mSTO/SRO interfaces, (m= 0, 2, or 4 unit cells), considering both the RuO6octahedra tilts and magnetic SRO electrodes. Our main results may be summarized as follows: i) The band alignment schemes predict that polarization direction may determine both Schottky barrier or Ohmic contacts form(STO)=0, but only Schottky contacts form(STO)=2 and 4 junctions; ii) The tunnel electroresistance and tunnel magnetoresistance ratios are evaluated at 0 and 300 K; iii) The most magnetoelectric responsive interfaces are obtained for them(STO)=2 heterostructure, this system also showing co-existent giant tunnel electroresistance and tunnel magnetoresistance effects; iv) The interfacial magnetoelectric coupling is not strong enough to control the tunnel magnetoresistance by polarization switching, in spite of significant SRO ferromagnetism.

Metastable doubly charged Rydberg trimers

We examine an effectively one-electron system with three positive nuclei composed of a Rb*87 Rydberg atom interacting with a pair of Rb+87 ions and predict the existence of metastable vibrationally bound states of Rb32+87. These molecules are long-range trimers whose stability rests on the presence of core-shell electrons and favorable scaling of the Rydberg atom's quadrupole moment with the principal quantum number n. Unlike recently observed ion-Rydberg dimers, whose binding is due to internal flipping of the Rydberg atom's dipole moment, the binding of Rb32+87 arises from the interaction of the ions with the Rydberg atom's quadrupole moment. The stability of these trimers is highly sensitive to n. For n≤35, we estimate that the lifetime of the bound states should be limited by intercore tunneling of the Rydberg electron, which creates an instability in the system. However, we predict that the rate of this process decreases significantly with n, such that already for n=38 it is comparable in magnitude to the rate of spontaneous emission of the Rydberg state. The decreasing depth of the binding potential at larger n will further lead to an increase in the tunneling rate of the vibrational states from the molecular binding potential to dissociative regions of the adiabatic potential energy surface. Nonetheless, at n=38, this mechanism is only relevant for the highest-excited vibrational states in the binding potential. Published by the American Physical Society 2024

Retina-Inspired X-Ray Optoelectronic Synapse Using Amorphous Ga2O3 Thin Film.

Machine vision techniques are widely applied for object identification in daily life and industrial production, where images are captured and processed by sensors, memories, and processing units sequentially. Neuromorphic optoelectronic synapses, as a preferable option to promote the efficiency of image recognition, are hotly pursued in non-ionizing radiation range, but rarely in ionizing radiation including X-rays. Here, the study proposes an X-ray optoelectronic synapse using amorphous Ga2O3 (a-Ga2O3) thin film. Boosted by the interfacial VO 2+ defects and its slow neutralization rate, the enhanced electron tunneling process at metal/a-Ga2O3 interface produces remarkable X-ray-induced post-synaptic current, contributing to a sensitivity of 20.5, 64.3, 164.1 µC mGy-1 cm-2 for the 1st, 5th, and 10th excitation periods, respectively. Further, a 64×64 imaging sensor is constructed on a commercial amorphous Si (a-Si) thin film transistor (TFT) array. The image contrast can be apparently improved under a series of X-ray pulses due to an outstanding long-term plasticity of the single pixel, which is beneficial to the subsequent image recognition and classification based on artificial neural network. The merits of large-scale production ability and good compatibility with modern microelectronic techniques belonging to amorphous oxide semiconductors may promote the development of neuro-inspired X-ray imagers and corresponding machine vision systems.

Optimal design of electrical conductivity of hybrid multi-dimensional carbon fillers reinforced porous cement-based Composites: Experiment and modelling

Cement-based composites with tailored electrical conductivity have promising applications in various intelligent and multifunctional infrastructures. Hybrid reinforcement using multi-dimensional carbon nanofillers is an effective approach for tailoring. However, determining the optimal recipe while balancing electrical properties and cost is challenging, which has not been carried out previously. This study develops a comprehensive micromechanical model with imperfect micromorphology, interface effect and electron tunneling to predict the electrical conductivity of cement-based composites reinforced with different combinations of 0D (zero-dimensional)-carbon black (CB), 1D-carbon nanotube (CNT) and 2D-graphene nanoplatelet (GNP). The influence of pore orientation on the electrical conductivity of the carbon nanofiller reinforced cement-based composites (CNRCCs) is studied for the first time and an effective conductive cross-sectional area method is proposed to investigate the anisotropy of the electrical conductivity in the CNRCCs. Furthermore, this model captures the synergistic effects of the hybrid carbon nanofillers, which has not been addressed in existing theoretical work on conductive composites. The developed model exhibits outstanding agreement with the experimental data of various samples. The optimal proportions for maximum electrical conductivity and performance-to-cost ratio are identified, such as mixing ratios of 80:20 for 0D-CB + 1D-CNT, 50:50 to 70:30 for 0D-CB + 2D-GNP, and 90:10 for 1D-CNT + 2D-GNP. The work is envisaged to provide guidelines for optimizing the performances of CNRCCs with tailored electrical properties and moderate cost.

EXTH-61. TOWARDS A QUANTUM THERAPY FOR GLIOBLASTOMA: A NEW THERAPEUTIC PARADIGM IN MEDICINE

Abstract BACKGROUND A cell operates as an interconnected bioelectrical circuit, utilising electron transfer processes for intracellular communication, with cytochrome c (Cyt c) playing a pivotal role. The redox processes of Cyt c, occurring via electron tunnelling, are essential for its translocation into the cytosol and modulation of its conformation to bind apoptotic protease activating factor 1. This highlights the need for novel technologies capable of interacting with these processes at the atomic scale to control downstream effects and induce apoptosis in cancer cells. METHODS We demonstrate that ‘bio-nanoantennae’, when supplied with an electrical current, enable quantum biological tunnelling for electron transfer (QBET) and facilitate cellular apoptosis in patient-derived IDH wild-type glioblastoma from both the infiltrative tumour margin and proliferative core. The bio-nanoantennae were constructed from gold nanoparticles functionalised with reduced Cyt c and zinc porphyrin as a redox couple. RESULTS Electrical polarisation of these bio-nanoantennae via resonant alternating currents in preclinical glioblastoma cells led to decreased metabolic activity and reduced cell viability by oxidizing Cyt c, thus inducing cellular stress. No significant effect was observed in healthy human astrocyte counterparts. The cytosol localised bio-nanoantennae induced differential gene expression related to ion channels, apoptosis, cancer proliferation and tumour suppression upon activation, in tumour relative to astrocyte cell populations. The bio-nanoantennae were also tested in 3D glioblastoma spheroid models, showing similar effects, and in vivo studies demonstrated a significant reduction in glioblastoma xenograft tumour size. CONCLUSION We propose that bio-nanoantennae modulate the redox state of Cyt c under an electrical field through QBET. To validate this, we investigated the tunnel junction energy and plasmon resonance scattering, and developed a mathematical model to explain the system’s behaviour. This innovative wireless electrical–molecular nanodevice, capable of inducing cancer cell apoptosis, paves the way for further applications of quantum signalling as a new (non-pharmacological) therapeutic paradigm.

Picometer Scale Photothermal Tuning of Plasmonic Nanocavities and Interfacial Processes.

The ability to precisely tune plasmon resonances is critical for advancing nanophotonic and sensing technologies. In this work, we exploit the photothermal effect to achieve picometer-level tunability of plasmon resonances in nanorod-on-mirror nanocavities, using polyelectrolyte (PE) layers as dielectric spacers. The plasmon-induced thermal response of these soft materials allows real-time adjustment of the nanocavity, unlike stable inorganic spacers like aluminum oxide. Under continuous laser illumination, the PE spacers undergo thickness reduction and phase transitions, leading to significant shifts in plasmon resonances. These shifts are influenced by laser power and initial spacer thickness, which govern near-field enhancement and photothermal effects. It is shown that this precise tuning capability enables the exploration of various photophysical processes, including the excitation of higher-order plasmon modes, optomechanical enhancement of surface-enhanced Raman scattering signals, electron tunneling, molecular diffusion from the nanocavities, and the transition to charge transfer plasmons.

Magnetic Excitations in Ferromagnetically Coupled Spin-1 Nanographenes.

In the pursuit of high-spin building blocks for the formation of covalently bonded 1D or 2D materials with controlled magnetic interactions, -electron magnetism offers an ideal framework to engineer ferromagnetic interactions between nanographenes. As a first step in this direction, we explore the spin properties of ferromagnetically coupled triangulenes-triangular nanographenes with spin . By combining in-solution synthesis of rationally designed molecular precursors with on-surface synthesis, we successfully achieve covalently bonded triangulene dimers and trimers on Au(111). Starting with the triangulene dimer, we meticulously characterize its low-energy magnetic excitations using inelastic electron tunneling spectroscopy (IETS). IETS reveals conductance steps corresponding to a quintet-to-triplet excitation, and a zero-bias peak resulting from higher-order spin-spin scattering of the five-fold degenerate ferromagnetic ground state. The Heisenberg model captures the key parameters of inter-triangulene ferromagnetic exchange, and its successful extension to the larger system validates the model's accuracy. We anticipate that incorporating ferromagnetically coupled building blocks into the repertoire of magnetic nanographenes will unlock new possibilities for designing carbon nanomaterials with complex magnetic ground states.

A two-dimensional TaGe2P4–WSi2As4 van der Waals heterojunction: A near-ideal rectifier

Searching for suitable 2D metal-semiconductor interfaces to design high-performance Schottky diodes is essential for the continuous miniaturization of devices. Herein, by using the first-principles calculations, we propose a near-ideal two-dimensional van der Waals rectifier consisting of the monolayer TaGe2P4 metal and the WSi2As4 semiconductor with ultra-clean interface and free dangling bonds. The van der Waals heterojunction has a p-type Schottky contact at both the vertical and lateral interfaces. The Schottky barriers lead to the asymmetry of electronic transport under the positive and negative bias voltages, thus resulting in a remarkable rectification behavior. The rectifying properties can be improved by regulating the length of the semiconductor and the overlapping region, and an ultra-high rectification ratio of 107 is obtained at a low bias voltage. The origin of the rectification effect and the regulating mechanism are explained in terms of the projected local density of states, transmission eigenstates, potential drop, and transmission spectra. It is found that increasing the relative length of the semiconductive part in the device enlarges the width of the Schottky barrier, which largely reduces the reverse current dominated by the electron tunneling while little affects the positive current, and thus leads to a significant improvement in the rectification performance. These results suggest that the TaGe2P4–WSi2As4 van der Waals heterojunction has promising application as a near-ideal rectifier.

An investigation into instantaneously tuning the EMI shielding characteristics of CNT-based nanocomposite biofoams in the X-band range by strain loading

The electromagnetic interference (EMI) shielding of CNT-based nanocomposite biofoams is capable of being tailored instantaneously by mechanical loading. In contrast to tuning the EMI shielding via nanofillers or by decoration process, the strain-activated EMI tailoring characteristics possess enormous potential that still await to be explored. To reveal this tailoring mechanism, a multi-scale electro-magneto-mechanically coupled homogenization model is developed to tailor the EMI characteristics of CNT-based nanocomposite biofoams in the X-band range (8.2–12.4 GHz). In this development, the elastic moduli, complex conductivity, and complex permeability are all selected as the homogenization variables. Four categories of interface effects are considered, including imperfect interface bonding, electron tunneling, Maxwell-Wagner-Sillars polarization, and electron hopping. The predicted EMI tailoring characteristics are validated by the experiment of CNT/wheat flour nanocomposite biofoam over a wide range of stain loading. The effective EMI shielding behavior decreases with the compressive loading, but it increases with the tensile loading. It is found that a CNT content higher than the percolation threshold is necessary to tailor the EMI shielding behavior of this nanocomposite foam via strain loading. This study can provide innovative insights to tune the EMI shielding characteristics of CNT-based nanocomposite biofoams in X-band instantaneously.

Adopting Buffer Layer for Improving Signal‐to‐Noise Ratio of Broadband Photomultiplication Type Organic Photodetectors

AbstractThe photomultiplication type organic photodetectors (PM‐OPDs) are prepared with structure of ITO/PNDIT‐F3N/F8BT/Y6‐1O:P3HT (100:3, wt/wt)/Al, containing hole traps formed with P3HT surrounded by Y6‐1O in active layers. The PM‐OPDs exhibit external quantum efficiency (EQE)&gt;100% in the spectral response range from 310 to 910 nm, resulting from electron tunneling injection assisted by trapped hole near ITO electrode. The incorporation of F8BT buffer layers can induce the markedly decreased dark current density (JD) due to the large electron injection barrier. The light current density (JL) of PM‐OPDs exhibits slightly decreased by inserting F8BT buffer layers due to the enhanced electron tunneling injection assisted by the more trapped holes near ITO electrode. The signal‐to‐noise ratio (SNR) of PM‐OPDs achieves over 40‐fold increment by inserting appropriate thickness of F8BT buffer layers, resulting from the markedly decreased JD and reasonably high JL. The optimal PM‐OPDs exhibit excellent photodetection capability with EQE of 4200% at 360 nm and 6600% at 850 nm, associated with the specific detectivity of 3.9 × 1011 Jones at 360 nm and 9.7 × 1011 Jones at 850 nm.

Theory of Electron Spin Resonance Spectroscopy in Scanning Tunneling Microscopy.

The integration of scanning tunneling microscopy (STM) and electron spin resonance (ESR) spectroscopy has emerged as a powerful and innovative tool for discerning spin excitations and spin-spin interactions within atoms and molecules adsorbed on surfaces. However, the origin of the STM-ESR signal and the underlying mechanisms that govern the essential features of the measured spectra have remained elusive, thereby significantly impeding the future development of the STM-ESR approach. Here, we construct a model to carry out precise numerical simulations of STM-ESR spectra for a single hydrogenated Ti adatom and a hydrogenated Ti dimer, achieving excellent agreement with experimental observations. We further develop an analytic theory that elucidates the fundamental origin of the signal as well as the essential features in the measured spectra. These new theoretical developments establish a solid foundation for the on-demand detection and manipulation of atomic-scale spin states, with promising implications for cutting-edge applications in spin sensing, quantum information, and quantum computing.

High‐Gain and Tunable Linear Photodetection in 2D Tunneling Heterostructures Through Potential Engineering

Abstract2D materials are extensively employed in the fabrication of high‐performance photodetectors owing to their exceptional physical properties. However, most 2D material photodetectors fail to sustain high gain under intense illumination due to the limited intrinsic trap states. Here, an n‐n type Bi2O2Se/SnSe2 van der Waals tunneling heterojunction photodetector with a detection range from visible to near‐infrared (VIS‐NIR) is presented. Under reverse bias, the heterojunction induces a significant electron barrier and hole potential well, ensuring low leakage current and ample hole defect states. Therefore, the photodetector demonstrated a responsivity of 1636.3 AW−1 and a detectivity of 1.39 × 1014 Jones under 660 nm illumination, maintaining a tunable linear dynamic range (LDR) of ≈74.7 dB. This performance is attributed to the hole potential well‐suppressing the recombination of photogenerated carriers, thereby enhancing the device's gain. Furthermore, the tunneling of photogenerated electrons within the heterojunction's space charge region under bias enables rapid response (75.1 and 15.6 µs). In summary, the study introduces a novel strategy to overcome the limited detection capabilities of 2D devices under intense illumination, characterized by outstanding linearity for rapid detection and high‐resolution imaging.

Quantum mechanical effects in plasmonic sub-nanometer cavities formed by a tip and substrate structure.

Enhancing local field intensity through light field compression is one of the core issues in surface plasmon-enhanced spectroscopy. The theoretical framework for the nanostructure composed of a tip and a substrate has predominantly relied on classical electromagnetic models, ignoring the electron tunneling effect. In this paper, we investigate the plasmonic near-field characteristics in the sub-nanometer cavity formed by the tip and the substrate using a quantum-corrected model. Additionally, we analyze the local electric field and Raman enhancement when hexagonal boron nitride (h-BN) monolayer is used as a decoupling layer for the nanocavity. The results indicate that classical electromagnetic theory fails to accurately describe the plasmonic electric field in smaller sub-nanometer gaps. When the gap is reduced to 0.32 nm, the quantum-corrected model shows that the local electric field in the sub-nanometer cavity is significantly reduced due to the tunneling current, aligning more closely with experimental results. Moreover, adding a high-barrier h-BN layer effectively prevents the occurrence of tunneling current, allowing for a strong local electric field even when the gap is less than 0.32 nm. The calculated maximum Raman enhancement reaches up to 15 orders of magnitude. Our research results provide a deep understanding of quantum mechanical effects in tip-enhanced spectroscopy systems, enabling the potential applications based on quantum plasmons in nanocavity.

Mild polarization electric field in ultra-thin BN-Fe-graphene sandwich structure for efficient nitrogen reduction

The electrocatalytic N2 reduction reaction (NRR) is expected to supersede the traditional Haber-Bosch technology for NH3 production under ambient conditions. The activity and selectivity of electrochemical NRR are restricted to a strong polarized electric field induced by the catalyst, correct electron transfer direction, and electron tunneling distance between bare electrode and active sites. By coupling the chemical vapor deposition method with the poly(methyl methacylate)-transfer method, an ultrathin sandwich catalyst, i.e., Fe atoms (polarized electric field layer) sandwiched between ultrathin (within electron tunneling distance) BN (catalyst layer) and graphene film (conducting layer), is fabricated for electrocatalytic NRR. The sandwich catalyst not only controls the transfer of electrons to the BN surface in the correct direction under applied voltage but also suppresses hydrogen evolution reaction by constructing a neutral polarization electric field without metal exposure. The sandwich electrocatalyst NRR system achieve NH3 yield of 8.9 μg h−1 cm−2 and Faradaic Efficiency of 21.7%. The N2 adsorption, activation, and polarization electric field changes of three sandwich catalysts (BN-Fe-G, BN-Fe-BN, and G-Fe-G) during the electrocatalytic NRR are investigated by experiments and density functional theory simulations. Driven by applied voltage, the neutral polarized electric field induced by BN-Fe-G leads to the high activity of electrocatalytic NRR.