Electrical Gating Research Articles

Development of intelligent automatic water intake system for open-pit mine

In order to solve the problem that the automation level of water intake system in open-pit mine is relatively low and the phenomenon of fault shutdown occurs from time to time, this paper innovatively develops an intelligent automatic water intake system based on LabVIEW suitable for open-pit mine. On the basis of extensive investigation of field conditions and in-depth analysis of domestic and foreign open-pit mine water intake system, the overall design scheme of this system was put forward. The selection of electric gate valve, ball valve, various sensors and Siemens 1200 series PLC was completed. The system software which integrates system initialization subroutine, pump rotation start-stop subroutine, sensor polling subroutine, fault protection and alarm subroutine was compiled. The monitoring software of Upper machine was developed based on LabVIEW software platform. The field debugging and operation results show that the system realizes the real-time monitoring of the operation state of the water intake unit, the on-demand start and stop and the intelligent rotation control of the water pump, which greatly reduces the labor intensity of the workers, prolongs the service life of the equipment, greatly improves the intelligent operation and maintenance level of pumping units of open-pit mine, and lays a solid foundation for green mining.

Dissipationless Circulating Currents and Fringe Magnetic Fields Near a Single Spin Embedded in a Two-Dimensional Electron Gas.

Theoretical calculations predict the anisotropic dissipationless circulating current induced by a spin defect in a two-dimensional electron gas. The shape and spatial extent of these dissipationless circulating currents depend dramatically on the relative strengths of spin-orbit fields with differing spatial symmetry, offering the potential to use an electric gate to manipulate nanoscale magnetic fields and couple magnetic defects. The spatial structure of the magnetic field produced by this current is calculated and provides a direct way to measure the spin-orbit fields of the host, as well as the defect spin orientation, e.g., through scanning nanoscale magnetometry.

Tunable transparent terahertz absorber for sensing and radiation warming

The lack in efficient functional devices has hindered plenty practical applications in terahertz (THz) band. In this work, we developed transparent THz absorber by employing trilayer Salisbury screen structure. Monolayer graphene and indium tin oxide (ITO) glass were spaced by a thin dielectric film, forming a transparent THz absorber. Assisted by ion gel, the carrier density of graphene layer can be effectively tuned through small external electrical gating (−2.5 V-2.5 V), with a modulation depth reaching to 100%. Taking advantage of the strong π−π interaction between graphene and external molecules containing π electrons, our fabricated transparent THz absorber enabled diphenylamine (DPA) detection. The adsorbed DPA molecule moves Fermi level of graphene toward Dirac point, performing a limit of detection of 5.5 ng. Moreover, by transferring the absorbed radiation into heat, our fabricated absorber can serve as a radiation warming device. The surface temperature of transparent THz absorber is 0.7 °C higher than that of glass in IR radiation environment. Note that the absorber is highly transparent in visible band, it will not prevent photosynthesis process of plants. Thereby, the THz absorbers have potential practical applications in diverse fields including wave manipulation, molecule sensing, and radiation warming.

Improved fault diagnosis method of electric gate valve in nuclear power plant

The vibration signal (VS) analysis and acoustic emission signal (AES) analysis methods are the common effective diagnostic methods in valve fault diagnosis (FD)(Classify fault types). However, these two methods are disadvantaged by the surrounding environment and noise signals produced during acquisition. To obtain an improved FD effect of an electric gate valve (EGV) in nuclear power plant, the two previous methods are ameliorated by a noise reduction processing, then the signal feature extraction is performed. The FD and degree evaluation are carried out for the common fault types of the EGV taken as object. In this paper, three-phase unbalanced faults (Acquisition of VS), packing damage faults (Acquisition of VS) and internal leakage faults (Acquisition of AES) are taken as examples. The Complete Ensemble Empirical Mode Decomposition with Adaptive Noise (CEEMDAN) algorithm composed with Fast Fourier Transform (FFT) and the SAEU3H series digital acoustic emission detection system (SAEU3H SDAEDS) are used to noise reduction and extraction of parameters of the VS and AES, respectively. Then, the extracted feature parameters are brought into the Bi-directional Long Short-Term Memory (Bi-LSTM) deep neural network for FD and fault degree evaluation (Assess the severity of failure occurrences). The experimental results show that the method adopted in this paper has high FD accuracy and low fault evaluation error.

Research on fault diagnosis method of electric gate valve under strong background noise

Electric gate valves are essential equipment in nuclear power plants. The safe and stable operation of an electric gate valve is key in maintaining the safety of nuclear power plant. However, due to the strong surrounding noise during the signal acquisition process that affect nuclear power plant electric gate valves, the early status monitoring and fault diagnosis of the electric gate valve are ineffective. However, the traditional fault diagnosis methods are not suitable for electric gate valves and fail to classify faults classification under the strong background noise. To achieve the noise reduction of electric gate valve acceleration signals based on strong background noise, the work proposes a Variational Mode Decomposition (VMD) method to denoise the strong noise in the collected signal. Seven genetic optimization algorithms are combined with VMD to enhance the model parameter selection of VMD. This selection criterion helps to select the most suitable algorithm combination for processing the acceleration signal of the electric gate valve under the background of strong noise. In order to obtain a better fault classification effect, the weak noise in the acceleration signal is further removed by Singular Value Decomposition (SVD). Moreover, the time-domain feature parameter extraction is performed on the denoised acceleration signal. Consequently, the model training of the Bidirectional Gate Recurrent Unit (BGRU) and the development of the electric gate valve fault diagnosis system under the background of strong noise are completed. The final experimental results show that the system developed in this paper has a good fault classification effect.

Intrinsic Nonlinear Hall Detection of the Néel Vector for Two-Dimensional Antiferromagnetic Spintronics.

The respective unique merit of antiferromagnets and two-dimensional (2D) materials in spintronic applications inspires us to exploit 2D antiferromagnetic spintronics. However, the detection of the Néel vector in 2D antiferromagnets remains a great challenge because the measured signals usually decrease significantly in the 2D limit. Here we propose that the Néel vector of 2D antiferromagnets can be efficiently detected by the intrinsic nonlinear Hall (INH) effect which exhibits unexpected significant signals. As a specific example, we show that the INH conductivity of the monolayer manganese chalcogenides MnX (X=S, Se, Te) can reach the order of nm·mA/V^{2}, which is orders of magnitude larger than experimental values of paradigmatic antiferromagnetic spintronic materials. The INH effect can be accurately controlled by shifting the chemical potential around the band edge, which is experimentally feasible via electric gating or charge doping. Moreover, we explicitly demonstrate its 2π-periodic dependence on the Néel vector orientation based on an effective k·p model. Our findings enable flexible design schemes and promising material platforms for spintronic memory device applications based on 2D antiferromagnets.

Ultrafast Subpicosecond Magnetization of a 2D Ferromagnet.

Strong spin-charge interactions in several ferromagnets are expected to lead to subpicosecond (sub-ps) magnetization of the magnetic materials through control of the carrier characteristics via electrical means, which is essential for ultrafast spin-based electronic devices. Thus far, ultrafast control of magnetization has been realized by optically pumping a large number of carriers into the d or f orbitals of a ferromagnet; however, it is extremely challenging to implement by electrical gating. This work demonstrates a new method for sub-ps magnetization manipulation called wavefunction engineering, in which only the spatial distribution (wavefunction) of s (or p) electrons is controlled and no change is required in the total carrier density. Usinga ferromagnetic semiconductor (FMS) (In,Fe)As quantum well (QW), instant enhancement, as fast as 600fs, of the magnetization is observed upon irradiating a femtosecond (fs) laser pulse. Theoreticalanalysis shows that the instant enhancement of the magnetization is induced when the 2D electron wavefunctions (WFs) in the FMS QW are rapidly moved by a photo-Dember electric field formed by an asymmetric distribution of the photocarriers. Because this WF engineering method can be equivalently implemented by applying a gate electric field, these results open a new way to realize ultrafast magnetic storage and spin-based information processing in present electronic systems.

Regulating Terahertz Photoconductivity in Two-Dimensional Materials

Two-dimensional materials represented by graphene have attracted extensive interest owing to the unique layer-dependent physical properties that are tunable with various external fields. In addition, by stacking two or more 2D materials together, a new material with the desired properties can be tailored and designed. Fully understanding the dynamical photoconductive response in 2D materials is uttermost important to design and develop the advanced optoelectronic devices. Terahertz (THz) time-domain spectroscopy (TDS) and time-resolved THz spectroscopy are powerful spectroscopic tools with the advantages of being contact-free and noninvasive, which have been widely used to study the photoconductivity (PC) of 2D materials. In this review, firstly, we provide a short introduction of the 2D materials and THz spectroscopy, and then a brief introduction of the experimental setup and experimental data analysis based on time-resolved THz spectroscopy are presented. After that, we overview the latest progress on the regulation of the THz PC that includes: (1) regulating the THz PC of graphene (Gr) and transition metal dichalcogenide (TMD) thin films with oxygen adsorption; (2) regulating the THz PC of Gr and Gr/TMDs heterostructures by electric gating and a built-in field introduced by a substrate; (3) regulating the THz PC of Gr/TMD heterostructures via optical gating; and (4) we overview the latest progress on the observation of elementary excitations in 2D materials with THz PC spectra following optical excitation and THz PC regulation via the photoexcitation of quasi-particles. Finally, we conclude the review and present a short overview of future research directions.

Atomic-scale tailoring of chemisorbed atomic oxygen on epitaxial graphene for graphene-based electronic devices

Graphene, with its unique band structure, mechanical stability, and high charge mobility, holds great promise for next-generation electronics. Nevertheless, its zero bandgap challenges the control of current flow through electrical gating, consequently limiting its practical applications. Recent research indicates that atomic oxygen can oxidize epitaxial graphene in a vacuum without causing unwanted damage. In this study, we have investigated the effects of chemisorbed atomic oxygen on the electronic properties of epitaxial graphene using scanning tunneling microscopy (STM). Our findings reveal that oxygen atoms effectively modify the electronic states of graphene, resulting in a bandgap at its Dirac point. Furthermore, we demonstrate that it is possible to selectively induce desorption or hopping of oxygen atoms with atomic precision by applying appropriate bias sweeps with an STM tip. These results suggest the potential for atomic-scale tailoring of graphene oxide, enabling the development of graphene-based atomic-scale electronic devices.

Orbital Fulde-Ferrell Pairing State in Moiré Ising Superconductors.

In this Letter, we study superconducting moiré homobilayer transition metal dichalcogenides where the Ising spin-orbit coupling (SOC) is much larger than the moiré bandwidth. We call such noncentrosymmetric superconductors, moiré Ising superconductors. Because of the large Ising SOC, the depairing effect caused by the Zeeman field is negligible and the in-plane upper critical field (B_{c2}) is determined by the orbital effects. This allows us to study the effect of large orbital fields. Interestingly, when the applied in-plane field is larger than the conventional orbital B_{c2}, a finite-momentum pairing phase would appear which we call the orbital Fulde-Ferrell (FF) state. In this state, the Cooper pairs acquire a net momentum of 2q_{B}, where 2q_{B}=eBd is the momentum shift caused by the magnetic field B and d denotes the layer separation. This orbital field-driven FF state is different from the conventional FF state driven by Zeeman effects in Rashba superconductors. Remarkably, we predict that the FF pairing would result in a giant superconducting diode effect under electric gating when layer asymmetry is induced. An upturn of the B_{c2} as the temperature is lowered, coupled with the giant superconducting diode effect, would allow the detection of the orbital FF state.

Minority carrier diffusion length in interface-confined PbS colloidal quantum dot (CQD): Effect of CQD surface modification on diffusion length in ultrathin PbS CQD films

Photocurrent microscopy (PCM) is a versatile tool for probing charge carrier transport associated with energy band bending at an interface. For the first time, we report the ligand-dependent electronic properties of interface-confined colloidal quantum dots (CQDs) near a metal electrode and gate dielectric layers using ultrathin lead sulfide (PbS) CQD films embedded in field effect transistors (FETs). We have compared the minority carrier (electron) diffusion length (MCDL) of ultrathin PbS CQD films treated with 1,2-ethanedithiol (EDT) and ammonium sulfide ((NH4)2S) using a bottom-contact FET structure in combination with PCM. We found that the MCDL was greater in the EDT-treated PbS CQDs than in the (NH4)2S-treated PbS CQDs. The MCDL at the 2D carrier accumulation layer was observed to depend on the concentration of the majority carrier (hole). During effective electrical channel formation by electrical gating, the MCDL decreased with hole accumulation (decreasing gate voltage) in the p-channel (NH4)2S-treated PbS CQD FET, whereas it remained similar in the EDT-treated PbS CQD FET. The effect of the majority carrier concentration on the MCDL was more pronounced in the (NH4)2S-treated sample than in the EDT-treated sample. The difference in the MCDL is attributed to a difference in the surface trap density caused by different ligand treatments.

Angular-Dependent THz Modulator with Hybrid Metal-Graphene Metastructures.

The coupling effects of surface plasmon resonance (SPR) from metamaterials induce variation in both the frequency and intensity of plasmonic modes. Here, we report an angular-dependent THz modulator with hybrid metal-graphene metastructures. The metastructures composed of the period gold split-rod arrays on top of a monolayer graphene, which show redshift modulation in the THz region with an increasing incident angle due to the strong out-of-plane magnetic flux introduced by the clockwise circular current at the oblique incidence. By utilizing graphene-based actively tunable conductor with ion-gel electrical gating, the THz transmission can be significantly modified. The modulation depth of the hybrid metal-graphene metastructure modulator can reach ~37.6% at 0.62 THz with a gate voltage of -3 V. The theoretical modeling of transmitted dependency on frequency and incident angle is demonstrated at different Fermi energies, which fits well with the experimental results. This hybrid device can offer a useful method for THz applications (such as angle sensors or angular-resolved spectroscopy), where angle-dependent modulation is needed.

Ultrafast Tunable Terahertz-to-Visible Light Conversion through Thermal Radiation from Graphene Metamaterials.

Several technologies, including photodetection, imaging, and data communication, could greatly benefit from the availability of fast and controllable conversion of terahertz (THz) light to visible light. Here, we demonstrate that the exceptional properties and dynamics of electronic heat in graphene allow for a THz-to-visible conversion, which is switchable at a sub-nanosecond time scale. We show a tunable on/off ratio of more than 30 for the emitted visible light, achieved through electrical gating using a gate voltage on the order of 1 V. We also demonstrate that a grating-graphene metamaterial leads to an increase in THz-induced emitted power in the visible range by 2 orders of magnitude. The experimental results are in agreement with a thermodynamic model that describes blackbody radiation from the electron system heated through intraband Drude absorption of THz light. These results provide a promising route toward novel functionalities of optoelectronic technologies in the THz regime.

Unconventional correlated insulator in CrOCl-interfaced Bernal bilayer graphene

The realization of graphene gapped states with large on/off ratios over wide doping ranges remains challenging. Here, we investigate heterostructures based on Bernal-stacked bilayer graphene (BLG) atop few-layered CrOCl, exhibiting an over-1-GΩ-resistance insulating state in a widely accessible gate voltage range. The insulating state could be switched into a metallic state with an on/off ratio up to 107 by applying an in-plane electric field, heating, or gating. We tentatively associate the observed behavior to the formation of a surface state in CrOCl under vertical electric fields, promoting electron–electron (e–e) interactions in BLG via long-range Coulomb coupling. Consequently, at the charge neutrality point, a crossover from single particle insulating behavior to an unconventional correlated insulator is enabled, below an onset temperature. We demonstrate the application of the insulating state for the realization of a logic inverter operating at low temperatures. Our findings pave the way for future engineering of quantum electronic states based on interfacial charge coupling.

Inorganic Perovskite Quantum Dot-Mediated Photonic Multimodal Synapse

Artificial synapse is the basic unit of a neuromorphic computing system. However, there is a need to explore suitable synaptic devices for the emulation of synaptic dynamics. This study demonstrates a photonic multimodal synaptic device by implementing a perovskite quantum dot charge-trapping layer in the organic poly(3-hexylthiophene-2,5-diyl) (P3HT) channel transistor. The proposed device presents favorable band alignment that facilitates spatial separation of photogenerated charge carriers. The band alignment serves as the basis of optically induced charge trapping, which enables nonvolatile memory characteristics in the device. Furthermore, high photoresponse and excellent synaptic characteristics, such as short-term plasticity, long-term plasticity, excitatory postsynaptic current, and paired-pulse facilitation, are obtained through gate voltage regulation. Photosynaptic characteristics obtained from the device showed a multiwavelength response and a large dynamic range (∼103) that is suitable for realizing a highly accurate artificial neural network. Moreover, the device showed nearly linear synaptic weight update characteristics with incremental depression electric gate pulse. The simulation based on the experimental data showed excellent pattern recognition accuracy (∼85%) after 120 epochs. The results of this study demonstrate the feasibility of the device as an optical synapse in the next-generation neuromorphic system.

Theory of Excitons in Gated Bilayer Graphene Quantum Dots

We present a theory of excitons in gated bilayer graphene (BLG) quantum dots (QDs). Electrical gating of BLG opens an energy gap, turning this material into an electrically tunable semiconductor. Unlike in laterally gated semiconductor QDs, where electrons are attracted and holes repelled, we show here that lateral structuring of metallic gates results in a gated lateral QD confining both electrons and holes. Using an accurate atomistic approach and exact diagonalization tools, we describe strongly interacting electrons and holes forming an electrically tunable exciton. We find these excitons to be different from those found in semiconductor QDs and nanocrystals, with exciton energy tunable by voltage from the terahertz to far infrared (FIR) range. The conservation of spin, valley, and orbital angular momentum results in an exciton fine structure with a band of dark low-energy states, making this system a promising candidate for storage, detection and emission of photons in the terahertz range.

Nonlocal drag thermoelectricity generated by ferroelectric van der Waals heterostructures

The \textquotedblleft ferron\textquotedblright\ excitations of the electric-dipolar order carry energy as well as electric dipoles. Here we predict a nonlocal ferron drag effect in a ferroelectric on top of a metallic film: An electric current in the conductor generates a heat current in the ferroelectric by long-range charge-dipole interactions. The non-local Peltier and its reciprocal Seebeck effect can be controlled by electric gates and detected thermographically. We predict large effects for van der Waals ferroelectric films on graphene.

Signatures of hot carriers and hot phonons in the re-entrant metallic and semiconducting states of Moiré-gapped graphene

Stacking of graphene with hexagonal boron nitride (h-BN) can dramatically modify its bands from their usual linear form, opening a series of narrow minigaps that are separated by wider minibands. While the resulting spectrum offers strong potential for use in functional (opto)electronic devices, a proper understanding of the dynamics of hot carriers in these bands is a prerequisite for such applications. In this work, we therefore apply a strategy of rapid electrical pulsing to drive carriers in graphene/h-BN heterostructures deep into the dissipative limit of strong electron-phonon coupling. By using electrical gating to move the chemical potential through the “Moiré bands”, we demonstrate a cyclical evolution between metallic and semiconducting states. This behavior is captured in a self-consistent model of non-equilibrium transport that considers the competition of electrically driven inter-band tunneling and hot-carrier scattering by strongly non-equilibrium phonons. Overall, our results demonstrate how a treatment of the dynamics of both hot carriers and hot phonons is essential to understanding the properties of functional graphene superlattices.

Inverse Design of a Hybrid Mie-Tamm Photonic Structure as a Highly Directional Gigahertz Single-Photon Source

We present a photonic structure where Mie, Tamm, and surface plasmon optical modes can be tailored to enhance the brightness of an embedded single-photon emitter. Contrary to most proposals, the structure is designed for excitation and collection through the substrate side. The front surface can be used instead to arrange metal contacts which serve both, as electrical gates and optical mirrors. The design is particularized for InGaAs QDs on GaAs resulting in an outcoupled single-photon rate exceeding 3 GHz in a narrow cone of NA = 0.17. The fabrication tolerances are also discussed.

Analytical investigation of a triple surrounding gate germanium source metal–oxide–semiconductor field‐effect transistor with step graded channel for biosensing applications

AbstractThis paper proposes a compact analytical model and comprehensively investigates the biosensing performance of a novel dielectric modulated triple surrounding gate germanium source metal–oxide–semiconductor field‐effect transistor with a step graded channel. Solving the 2D Poisson's equation yields an analytical expression of threshold voltage, channel potential, drain current and sub threshold swing. The sensitivity variation in the biosensor has been thoroughly studied by varying different device parameters to investigate its biosensing performance. Graded doping in channel offers enhanced sensitivity than a non‐graded doped channel when the doping of the channel is more near the drain end than source end which is due to stronger electric field and gate capacitance. Effect of fill‐in factor for different biomolecules on the sensitivity has been thoroughly discussed. Different analytical results show an excellent agreement with the simulations done on SILVACO ATLAS TCAD simulator.