Electric Doping Research Articles

Modulation of monolayer SnSe2 optoelectronic properties by applied electric field and atomic doping

Based on the first principles, we have calculated the influence of the applied electric field and doped X (X = N, P, As, Sb) atoms on the optoelectronic properties and phonon dispersion of the monolayer 2D material SnSe2. The calculation results show that intrinsic SnSe2 is a semiconductor with a band gap value of 0.884 eV. The doping of X atoms improves the energy band tunability of the monolayer SnSe2 system and becomes more stable. The N-doped SnSe2 system has the most stable structure and the best doping performance. When the electric field strength of 0.3 V/Å is applied on the surface of the N-doped system, the band gap of the system increases. The energy gap gradually decreases when the electric field strength continues to increase from 0.3 V/Å to 0.9 V/Å. At an applied electric field strength of 0.9 V/Å, the system changes from semiconductor to metallic properties. As far as the optical properties are concerned, the applied electric field increases the static refractive index of the system, the imaginary part of the photoconductivity increases, the energy loss function decreases, and the light absorption performance improves. The applied electric field successfully enhanced the optical properties of the SnSe2 system. The applied electric field strength of 0.9 V/Å doped N system has the best optical properties. This provides a new way to explore the optoelectronic devices based on the SnSe2 doped system.

Structural modulation of bilayer graphene under an external electric field and carrier doping

Density functional theory was used to investigate the geometric structure of bilayer graphene under an external electric field with carrier doping. Our calculations revealed the crucial impact of external electric fields and the hole injection on determining the geometric structure of bilayer graphene. The bond length of graphene monotonically increased when increasing the hole doping concentration, while it remained insensitive to electron doping. Additionally, there accumulated carriers predominantly distributed in the outermost layer located just below the gate electrode. These results enabled the construction of moiré superlattices in the bilayer graphene, possessing different moiré periodicity depending on the carrier concentration.

Identifying and Amplifying the Spontaneously Formed Photo‐Charge Contribution in Opaque and Semitransparent Organic Photovoltaics

AbstractSpontaneous photo‐charge (SP) generation within the non‐fullerene (NFA) bulk helps avoid exciton (EX) related loss as compared to the traditional heterojunction route in organic solar cells (OSCs). Unfortunately, the promising SP utilization attracts little attention at this time due to the lack of knowledge on its specific contribution to the photovoltaic performance and rational optimization in high‐efficiency devices. To fill the gap, the NFAs’ SP characteristics are related with their photocurrent loss and power conversion efficiency (PCE) in state‐of‐the‐art materials. Though higher SP population is good for efficient EX utilization, it simultaneously acts as an additional photo‐charge recombination channel. The former can be further enhanced by increasing the NFAs’ crystallinity with preferred lamellar growth, and the latter can be suppressed via electric doping. With the aid of the two‐step optimization strategy, the total photocurrent loss is reduced from 14.4% to 4.8%, accompanying with PCE increment from 16.9% to 18.5%. The SP utilization strategy is finally applied in the semitransparent OSCs (ST‐OSCs), due to its less heterojunction area sensitive photo‐charge generation characteristic. A light utilization efficiency (LUE) is then increased from 3.21% to 3.77%. The findings highlight the pursue of efficient SP utilization as a new design philosophy in future OSCs’ progresses.

Graphene-Based Tunable Dual-Frequency Terahertz Sensor.

A tunable dual-band terahertz sensor based on graphene is proposed. The sensor consists of a metal bottom layer, a middle dielectric layer, and single-layer graphene patterned with four strips on the top. The numerical simulations results show that the proposed sensor exhibits two significant absorption peaks at 2.58 THz and 6.07 THz. The corresponding absorption rates are as high as nearly 100% and 98%, respectively. The corresponding quality factor (Q) value is 11.8 at 2.58 THz and 29.6 at 6.07 THz. By adjusting the external electric field or chemical doping of graphene, the positions of the dual-frequency resonance peak can be dynamically tuned. The excitation of plasma resonance in graphene can illustrate the mechanism of the sensor. To verify the practical application of the device, the terahertz response of different kinds and different thicknesses of the analyte is investigated and analyzed. A phenomenon of obvious frequency shifts of the two resonance peaks can be observed. Therefore, the proposed sensor has great potential applications in terahertz fields, such as material characterization, medical diagnosis, and environmental monitoring.

Optimal operation of multi-integrated energy system based on multi-level Nash multi-stage robust

To address the challenges faced by an integrated energy system (IES) during independent operation, such as high operating costs and significant uncertainties in electricity prices and source-load, a cooperative operation method based on a three-level Nash three-stage robust optimization is proposed for the Multi-integrated energy system (MIES). Firstly, the IES is enhanced by incorporating the coupling of multiple energy flows (electricity, heat, hydrogen, and gas) through the integration of an electric hydrogen module (EHM) and gas hydrogen doping combined heat and power (GHDCHP). Secondly, a Nash-Stackelberg-Nash game framework is constructed using game theory to accurately capture the interaction characteristics between the MIES and the Multi-PV prosumer (MPVP). Subsequently, a three-stage robust optimization model is developed for the IES, taking into full consideration the multiple uncertainties in electricity prices and source-load. This model is coupled with the Nash-Stackelberg-Nash game to propose a three-level Nash three-stage robust optimization model. Additionally, an ADMM algorithm coupling AOP-Looped C&CG is proposed to effectively solve the model. Finally, the effectiveness of the proposed method is validated through numerical examples.

Restoration of spline surface of axial pump drive shaft by electric spark doping

This paper considers the possibility of restoring the splined surfaces of the drive shafts of axial pumps having specific wear by the electric spark doping (EIL) method, with the creation of coatings on their working surfaces, with corresponding mechanical characteristics. Electrode materials and processing modes are selected. Studies were carried out to determine the processing modes to obtain the optimal roughness of the applied coating. Keywords axial pump, electric spark doping, reduction, electrode materials, reduced energy, roughness

Nanoscale Manipulation of Exciton-Trion Interconversion in a MoSe2 Monolayer via Tip-Enhanced Cavity-Spectroscopy.

Emerging light-matter interactions in metal-semiconductor hybrid platforms have attracted considerable attention due to their potential applications in optoelectronic devices. Here, we demonstrate plasmon-induced near-field manipulation of trionic responses in a MoSe2 monolayer using tip-enhanced cavity-spectroscopy (TECS). The surface plasmon-polariton mode on the Au nanowire can locally manipulate the exciton (X0) and trion (X-) populations of MoSe2. Furthermore, we reveal that surface charges significantly influence the emission and interconversion processes of X0 and X-. In the TECS configuration, the localized plasmon significantly affects the distributions of X0 and X- due to the modified radiative decay rate. Additionally, within the TECS cavity, the electric doping effect and hot electron generation enable dynamic interconversion between X0 and X- at the nanoscale. This work advances our understanding of plasmon-exciton-hot electron interactions in metal-semiconductor-metal hybrid structures, providing a foundation for an optimal trion-based nano-optoelectronic platform.

Perovskite-based optoelectronic systems for neuromorphic computing

Brain-like neuromorphic computing system offers the ability to be used in neural networks on demand and are rapidly gaining interest by researchers due to their outstanding photoelectric stimulation response-ability and multi-segment storage function. In this work, we show the processing capabilities of the neuromorphic computing units for optoelectronic signals and high label noise ratio signals. Demonstrated the functions of potassium ion doped perovskite-based unit resembles properties found in neuronal synapses. Potassium ion passivates perovskite and promotes the formation of the electric double layer and ion doping in the unit so that the unit can simulate the characteristics of biological synapses generated by various electrical simulations according to the demand. Perovskite significantly enhances the unit's responsiveness to light pulses in the visible light range. By implementing the 'resolving training biases via influence-base data relabeling' strategy, the unit demonstrates remarkable performance in high noise recognition tasks. These results open a new direction for the construction of brain-like computers that deal with a complex and high proportion of harmful samples.

Cooperative alkaline hydrogen evolution via inducing local electric field and electron localization

Alkaline hydrogen evolution reaction (HER) represents a promising means to store intermittent renewable energy into clean energy. Unfortunately, the sluggish H2O dissociation and difficult *H adsorption-desorption are prominent obstacles to the development of alkaline HER. Herein, we developed a cooperative strategy via nanoneedle inducing local electric field and atomic doping causing electron localization for alkaline HER based on the preparation of Cu doped CoS2 nanoneedles (Cu-CoS2 NNs). Finite element method simulations and density functional theorycalculations demonstrate the local electric field accelerates H2O dissociation and electron localization facilitates *H adsorption, respectively. In situ attenuated total reflection infrared spectroscopy and electro-response measurement experimentally reveal the superior ability to H2O dissociation and *H adsorption for Cu-CoS2 NNs. As a result, the Cu-CoS2 NNs exhibit an ultralow overpotential of 64 mV at –10 mA cm−2 and long-term stability over 100 h at –100 mA cm−2 during alkaline HER, which outperforms most electrocatalysts in recently published works.

Modulating interlayer and intralayer excitons in WS2/WSe2 van der Waals heterostructures

Intralayer and interlayer excitons are fundamental quasiparticles that can appear simultaneously in transition metal dichalcogenide van der Waals heterostructures. The understanding and modulation of the interaction of interlayer and intralayer excitons are of great importance for both fundamental studies and device applications. Here, we demonstrate the modulation of photoluminescence (PL) emissions of interlayer and intralayer excitons in WSe2/WS2 heterostructures using different stacking configurations in a single sample, including with and without hexagonal boron nitride (hBN) encapsulation and different hBN spacing layers. By temperature dependent PL spectroscopy, we observed the suppression of interlayer exciton formation and exciton complexes at high temperatures due to enhanced phonon scattering. We also verify the formation of these states via power dependent spectroscopy. Our electric field and doping dependent PL studies reveal that the interlayer exciton peaks shift linearly with the applied gate voltage and the intralayer excitons of WSe2 (WS2) are dominant at high n-doping (p-doping). Our results contribute to the understanding of the interplay between interlayer and intralayer excitons in WSe2/WS2 heterostructures and could promote the related exitonic device applications.

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.

Electric field and charge doping induced superconducting transition in 2D freestanding perovskite barium bismuthate

Electric field and charge doping induced superconducting transition in 2D freestanding perovskite barium bismuthate

The Ability of CO2 Capture on Transition Metal-modified 1T'-MoS2 Monolayers Controlled by an Electric Field.

Herein, we evaluate the CO2 capture ability on the transition metal-modified 1T'-MoS2 monolayers (TM@1T'-MoS2 , TM represents a transition metal atom from 3d to 4d except Y, Tc and Cd) under different external electric fields via first-principles calculations. As the screened results revealed that Mo@1T'-MoS2 , Cu@1T'-MoS2 and Sc@1T'-MoS2 monolayers possess higher sensitivity for electric field than pristine 1T'-MoS2 monolayer. Among the above candidates, Mo@1T'-MoS2 and Cu@1T'-MoS2 monolayers only require the electric field strength of 0.002 a.u. to reversibly capture CO2 and can absorb up to four CO2 molecules with the electric field of 0.004 a.u. Furthermore, Mo@1T'-MoS2 can selectively capture CO2 molecule from the mixture of CH4 and CO2 . Our findings not only provide useful insights that the synergistic effect of electric field and transition metal doping is beneficial for CO2 capture and separation, but also guide the application of 1T'-MoS2 in the field of gas capture.

Enhanced superconductivity in spin-orbit proximitized bilayer graphene.

In the presence of a large perpendicular electric field, Bernal-stacked bilayer graphene (BLG) features several broken-symmetry metallic phases1-3 as well as magnetic-field-induced superconductivity1. The superconducting state is quite fragile, however, appearing only in a narrow window of density and with a maximum critical temperature Tc ≈ 30 mK. Here we show that placing monolayer tungsten diselenide (WSe2) on BLG promotes Cooper pairing to an extraordinary degree: superconductivity appears at zero magnetic field, exhibits an order of magnitude enhancement in Tc and occurs over a density range that is wider by a factor of eight. By mapping quantum oscillations in BLG-WSe2 as a function of electric field and doping, we establish that superconductivity emerges throughout a region for which the normal state is polarized, with two out of four spin-valley flavours predominantly populated. In-plane magnetic field measurements further reveal that superconductivity in BLG-WSe2 can exhibit striking dependence of the critical field on doping, with the Chandrasekhar-Clogston (Pauli) limit roughly obeyed on one end of the superconducting dome, yet sharply violated on the other. Moreover, the superconductivity arises only for perpendicular electric fields that push BLG hole wavefunctions towards WSe2, indicating that proximity-induced (Ising) spin-orbit coupling plays a key role in stabilizing the pairing. Our results pave the way for engineering robust, highly tunable and ultra-clean graphene-based superconductors.

Reversible Tuning of Superconductivity in Ion-Gated NbN Ultrathin Films by Self-Encapsulation with a High- κ Dielectric Layer

Ionic gating is a powerful technique for tuning the physical properties of a material via electric field-induced charge doping, but is prone to introduce extrinsic disorder and undesired electrochemical modifications in the gated material beyond pure electrostatics. Conversely, reversible, volatile and electrostatic modulation is pivotal in the reliable design and operation of novel device concepts enabled by the ultrahigh induced charge densities attainable via ionic gating. Here we demonstrate a simple and effective method to achieve reversible and volatile gating of surface-sensitive ultrathin niobium nitride films via controlled oxidation of their surface. The resulting niobium oxide encapsulation layer exhibits a capacitance comparable to that of non-encapsulated ionic transistors, withstands gate voltages beyond the electrochemical stability window of the gate electrolyte, and enables a fully-reversible tunability of both the normal-state resistivity and the superconducting transition temperature of the encapsulated films. Our approach should be transferable to other materials and device geometries where more standard encapsulation techniques are not readily applicable.

From Electric Doping Control to Thermal Defect Nucleation in Perovskites

AbstractSimultaneous optical microscopy and electric transport measurements on La0.7Sr0.3MnO3 nanobridges, grown on SrTiO3 (STO), show direct evidence of directional oxygen vacancy migration under large voltage bias. Comparative study on discontinuous structures, with voltages applied across a micron‐scale gap, demonstrates that high electric fields induce electrolytic modifications confined to the anode. Extensive electromigration is shown to induce the formation of linear surface scars on the STO substrate, following well defined crystallographic directions. The reproducible triggering of these surface dislocations is demonstrated, unveiling their thermal rather than electrical origin and it is shown that they do not represent electroformed conduction channels. High‐resolution scanning transmission electron microscopy imaging reveals that the scars correspond to nanometer scale steps caused by (101) gliding planes in the STO caused by the proliferation of edge dislocations and local lattice expansion. These findings shed light on selective electrically‐controlled atom migration and its role in structural modification of functional oxides, opening a unique avenue for ionotronic device design.

Two-dimensional graphyne–graphene heterostructure for all-carbon transistors

Semiconducting graphyne is a two-dimensional (2D) carbon allotrope with high mobility, which is promising for next generation all-carbon field effect transistors (FETs). In this work, the electronic properties of van der Waals heterostructure consists of 2D graphyne and graphene (GY/G) were studied from first-principles calculations. It is found that the band dispersion of isolated graphene and graphyne remain intact after they were stacked together. Due to the charge transfer from graphene to graphyne, the Fermi level of the GY/G heterostructure crosses the VB of graphene and the CB of graphyne. As a result, n-type Ohmic contact with zero Schottky barrier height (SBH) is obtained in GY/G based FETs. Moreover, the electron tunneling from graphene to graphyne is found to be efficient. Therefore, excellent electron transport properties can be expected in GY/G based FETs. Lastly, it is demonstrated that the SBH in the GY/G heterostructure can be tune by applying a vertical external electric field or doping, and the transition from n-type to p-type contact can be realized. These results show that GY/G is potentially suitable for 2D FETs, and provide insights into the development of all-carbon electronic devices.

Gate-induced half metals in Bernal-stacked graphene multilayers

Recent experiments indicate that the Bernal stacked graphene multilayer (BGM) have an interaction induced gapped (or pseudo gapped) ground state. Here, we propose that, due to the electron correlation, the BGM can be induced into a half metallic phase by applying a vertical electric field and doping. The half metallic states in even-layer and odd-layer BGMs have totally different behaviors, due to their different band structures. We systematically calculate the graphene tetralayer (4L-BGM) and trilayer (3L-BGM) as the typical examples of the even-layer and odd-layer BGMs, respectively. In 4L-BGM, we find an interesting phenomenon of electric field induced inversion of the spin-polarized bands. Namely, in the half metallic phase, the spin polarization of the conducting channel and the net magnetic moment are inversed when the applied electric field exceeds a critical value. In 3L-BGM, a remarkable feature is that the inequivalence of the the two sublattices will intrinsically break the degeneracy of the the spin-up and spin-down bands even in the zero electric field case. Our results suggest that 4L-BGM should be an ideal platform to detect the proposed half metallic phase in BGM systems.

Simultaneous Control of Bandfilling and Bandwidth in Electric Double-Layer Transistor Based on Organic Mott Insulator κ-(BEDT-TTF)2Cu[N(CN)2]Cl

The physics of quantum many-body systems have been studied using bulk correlated materials, and recently, moiré superlattices formed by atomic bilayers have appeared as a novel platform in which the carrier concentration and the band structures are highly tunable. In this brief review, we introduce an intermediate platform between those systems, namely, a band-filling- and bandwidth-tunable electric double-layer transistor based on a real organic Mott insulator κ-(BEDT-TTF)2Cu[N(CN)2]Cl. In the proximity of the bandwidth-control Mott transition at half filling, both electron and hole doping induced superconductivity (with almost identical transition temperatures) in the same sample. The normal state under electric double-layer doping exhibited non-Fermi liquid behaviors as in many correlated materials. The doping levels for the superconductivity and the non-Fermi liquid behaviors were highly doping-asymmetric. Model calculations based on the anisotropic triangular lattice explained many phenomena and the doping asymmetry, implying the importance of the noninteracting band structure (particularly the flat part of the band).

Quality assessment of AL-C-B coatings on steel surfaces obtained by electro spark alloying

Problem. As a rule, during the operation of the product, the surface layers of materials are most affected. These can be parts that work in aggressive environments, at high temperatures, various force actions, the presence of abrasive particles, etc. Under such conditions, different types of steels and alloys are used, and, most commonly, it is high-alloy, which significantly complicates the manufacturing process and increases the cost of the finished product. Diffusion coating methods are the most widespread in the industry, which is due to the best study and ease of these processes. However, there are alternative methods of surface treatment, which are devoid of the disadvantages of diffusion methods.
 The goal is to develop a method of obtaining boron-containing coatings of the Al-C-B system by the electro spark alloying (ESA), applying STS to the treated surface, to study the processes of structural and phase formation of surface layers depending on the energy processes of ESA and substrate material. Methology. Samples made of steel 20 and 40 were used for the study, on which a coating consisting of their sulfur ointment, aluminum powder, amorphous boron powder was applied. Without waiting for drying, the ESA surfaces of the samples were carried out with a graphite electrode on an installation with a discharge energy of 0.13, 0.55 and 4.9 J. The surface roughness after treatment was determined on a profilograph-profilometer by removing and processing profilograms. Metallographic analysis of coatings was performed using an MIM-7optical microscope, and durometric studies were made on the PMT-3 device according to standard methods. Results: the article presents the original method for obtaining boron-containing coatings of the Al-C-B system by the ESA method, which involves applying a coating consisting of sulfur ointment, aluminum powder, amorphous boron powder on the treated surface, followed by electric spark doping with a graphite electrode.