Dopant Research Articles

Electronic Structure Engineering of RuNi Alloys Decrypts Hydrogen and Hydroxyl Active Site Separation and Enhancement for Efficient Alkaline Hydrogen Evolution.

Rational design of the active sites of hydrolysis dissociation intermediates to weaken their active site competition and toxicity is a key challenge to achieve efficient and stable hydrogen evolution reaction (HER) in ruthenium-containing alloys. Density Functional Theory (DFT) simulations reveal that the transfer of the d-band electrons from Ru to Ni in RuNi alloys results in a Gibbs free energy of -0.12eV for the Ru0.250Ni Fcc-site H*. In addition, the high spin state of the electrons outside the Ru nucleus strengthens the adsorption of OH* on the Ru─Ni bond, which weakens the active-site competition and toxicity successfully. This theoretical prediction is confirmed by electrodeposition of prepared aRuxNi, and the RuNi alloys obtained by Ru atom doping have excellent HER properties. aRu0.250Ni has overpotentials of 38 and 162.4mV at -10 and -100mAcm-2, respectively, and can be stably operated at -100mAcm-2 Dual-electrode system aRu0.250Ni//bRu0Ni demonstrates an ultra-low battery voltage (1.86V @500mAcm-2) and excellent stability (24h@300mAcm-2). This holistic work resolves the mechanism of active site separation and strengthening in RuNi alloys, and provides a new design idea for the preparation of highly efficient alkaline HER electrodes.

N-P type charge compensatory synergistic effect for Schottky and efficient photoelectrocatalysis applications: Doping mechanism in (Nb/Re)@WS2/graphene heterojunctions.

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

Evaluating nonmetal atom doping in two-dimensional VSe2 monolayers for hydrogen and oxygen electrocatalysis

Evaluating nonmetal atom doping in two-dimensional VSe2 monolayers for hydrogen and oxygen electrocatalysis

Engineering multiple nano-twinned high entropy alloy electrocatalysts toward efficient water electrolysis

Inducing defects in high entropy alloys (HEAs) has been recognized as a promising approach for tuning surface energetics and catalytic activities. However, the comprehensive understanding and facile synthetic methods for defect-rich HEAs remain challenging. Herein, we present an interstitial-atom engineering strategy that involves interstitial atom doping to synthesize B-doped FeCoNiCuMoB HEA films containing abundant multiple nano-twin boundaries. The resulting fivefold-twinned FeCoNiCuMoB catalyst exhibits exceptional performance in alkaline hydrogen evolution reaction (HER, 26mV at -10 mA cm-2) and oxygen evolution reaction (OER, 201mV at 10mAcm-2). Notably, the two-electrode electrolyzer composed of the FeCoNiCuMoB film electrodes achieved the 10mAcm-2 at an ultralow cell voltage (1.48V) for water electrolysis, simultaneously maintaining long-term durability. Through in-situ Raman spectroscopy, X-ray absorption spectroscopy (XAS), electrochemical analyses, and density functional theory (DFT) calculations, we elucidate that the unique twin boundaries play a crucial role in tailoring surficial electronic structures. Moreover, election-rich B atoms display optimized atomic configurations, synergistically contributing to a thermodynamically favourable HER/OER pathway. This work provides a platform via interstitial-atom engineering for designing exceptional HEA catalysts, integrating planar defects and electronic effects, to enhance the efficiencies in water electrolysis applications.

P-type doped AlxGa1-xAs nanowire photocathode: A theoretical perspective on structural and optoelectronic properties

In this work, the effect of p-type doping on the structural, electronic, and optical properties of AlxGa1-xAs nanowires are investigated by first-principles calculations. Different doping elements (Be, Mg, Zn), doping methods (interstitial and substitution doping) and doping concentration are considered. The calculations of formation energy suggest that the structural stability of p-type AlxGa1-xAs nanowires is gradually weaken as the rise of doping concentration and Al composition. Besides, the difficulty of forming substitution doping for different doping elements obeys the following order: Be<Mg<Zn. In addition, the substitution doping atom tends to replace Ga atom rather than Al atom to form substitution doping structure. After substitution doping, all energy bands shift to higher energy region due to the orbital hybridization of electronic states induced by impurity atom and nanowire atoms. Moreover, the substitution doping leads to the Fermi level entering into the valence band, resulting in obviously p-type conductivity. The p-type modulation doping is indeed effective in the axial type AlxGa1-xAs nanowires with p-type carrier concentration varying between 1.85×1020 cm-3 and 4.42×1020 cm-3, and the conductivity will be further enhanced with increasing substitution doping concentration or Al composition. Finally, the optical absorption of AlxGa1-xAs nanowire photocathodes can be effectively enhanced through BeGa doping. Our findings not only present a comprehensive understanding of p-type doping mechanism of AlxGa1-xAs nanowires, but also provide a theoretical basis for preparing AlxGa1-xAs nanowire based photoelectric devices with p-type properties.

Influence of irradiation wavelength during laser-assisted doping of 4H-silicon carbide in liquid phase

Laser-assisted doping of silicon carbide (SiC) substrates is challenging due to the low diffusion coefficient of dopant atoms and the chemically inert nature of SiC. Single crystal intrinsic 4H-SiC substrate is irradiated with neodymium-doped yttrium aluminium garnet (Nd3+):YAG laser with wavelengths of 1064, 355 and 266 nm, and krypton fluoride (KrF) excimer laser with the wavelength of 248 nm under liquid phase dopant sources. Different liquid solutions were used as dopant sources for aluminium (Al) and phosphorus (P). SiC was transparent to 1064 and 355 nm due to low absorption coefficients, while 266 and 248 nm showed better coupling due to higher absorption coefficients and led to the diffusion of atoms. The electrical resistance of the substrates was measured to be lower than 1000 kΩ after diffusion. Dispersive X-ray spectroscopy (EDS) studies showed that both laser wavelengths of 248 nm and 266 nm resulted in doping of Al and P, with the surface concentrations ranging from 0.5 to 1.5 at.% and from 0.24 to 0.6 at.%, respectively. Two-dimensional thermo-temporal simulation of the laser pulse interaction in the liquid phase revealed that unlike in air, during irradiation with 266 nm laser under liquid, the surface temperature of the substrate was slightly lower. However, the subsurface temperature increased along the depth by a few microns. Similarly, simulation studies with longer pulse irradiation also show that high temperature was maintained for a longer time, indicating improved dopant diffusion into the 4H-SiC substrate.

Excitation wavelength and time dependent colour tunable room temperature phosphorescence from boron doped carbon nanodots.

Developing metal free room temperature phosphorescence (RTP) materials have received tremendous attention due its potential application in various fields such as sensing, optoelectronics and anticounterfeiting. Herein, we have synthesized an excitation wavelength and time dependent phosphorescent boron doped carbon nanodots (BCNDs) by thermal treatment of ethanolamine and boric acid at 240°C, where boric acid act as both doping and host agents. The obtained BCNDs display blue to orange fluorescence in both aqueous medium and solid state. In addition, the BCNDs display tunable orange-yellow-green phosphorescence in solid state under UV and visible light, lasting upto 10s, visible to naked eye. The boron and nitrogen doping regulates the band gap of the BCNDs, resulting the phosphorescence colour tunability. The average phosphorescence lifetime and quantum yield of BCNDs are found to be 1.27s and 8.61% respectively. Based on the optical properties, the BCNDs are applied as security ink in information encryption and security marking. Hence, this work can promote the development of metal free phosphorescent carbon based materials which may find application in various emerging fields.

Ultra-high precision nano additive manufacturing of metal oxide semiconductors via multi-photon lithography

As a basic component of the versatile semiconductor devices, metal oxides play a critical role in modern electronic information industry. However, ultra-high precision nanopatterning of metal oxides often involves multi-step lithography and transfer process, which is time-consuming and costly. Here, we report a strategy, using metal-organic compounds as solid precursor photoresist for multi-photon lithography and post-sintering, to realize ultra-high precision additive manufacturing of metal oxides. As a result, we gain metal oxides including ZnO, CuO and ZrO2 with a critical dimension of 35 nm, which sets a benchmark for additive manufacturing of metal oxides. Besides, atomic doping can be easily accomplished by including the target element in precursor photoresist, and heterogeneous structures can also be created by multiple multi-photon lithography, allowing this strategy to accommodate the requirements of various semiconductor devices. For instance, we fabricate an ZnO photodetector by the proposed strategy.

Synergistic Alkaline Hydrogen Evolution Catalysis over MoC Triggered by Doping Single Ru Atoms

AbstractThe rational design of single atom‐based catalysts and precise elucidation of the synergistic interaction between the metal site and substrate are pivotal to identifying the real active sites and explicating the catalytic mechanisms at the atomic scale, thus contributing to the development of high‐performance catalysts for diverse industrial implementations. Herein, a Ru single‐atom doping strategy is developed to activate the MoC substrate with superior hydrogen evolution reaction (HER) activity in an alkaline medium. The atomically dispersed Ru sites are elaborately doped into MoC nanoparticles loaded on 3D N‐doped carbon nanoflowers (Ru‐SAs@MoC/NCFs hereafter). The experimental results and theoretical calculations manifest that the atomically isolated Ru dopants can effectively trigger the Mo sites with thermodynamically favorable water adsorption/dissociation energies and facilitate the OH− desorption on Ru sites and H adsorption on N sites, thus synergistically expediating the overall alkaline HER kinetics. As such, the well‐designed Ru‐SAs@MoC/NCFs demonstrate extraordinary HER activity with a low overpotential of 16 mV at 10 mA cm−2 in 1.0 m KOH electrolyte, outperforming Pt/C benchmark and a vast of molybdenum/ruthenium‐based HER catalysts reported to date. These findings disclose the alkaline HER mechanistic induced by the atomic doping modulation and suggest a design principle of high‐efficiency electrocatalysts via the atomic‐level manipulation leverage.

Exploring the Multifunctional Properties of (Sr, Ni)‐Co‐Doped BaTiO3: Structural Characterization and Electromagnetic Characteristics

The structural and electromagnetic properties of various Ba1−x(Sr0.5Ni0.5)xTiO3 are extensively investigated. X‐ray diffraction and Rietveld refinement are used to perform a structural study. With doping substances, bulk and theoretical densities decrease. The crystallite size is calculated using Scherrer and Williamson–Hall method. The microstructural properties are examined using images from field‐emission scanning electron microscope. The observed values of dielectric constants are found to agree with the porosity‐corrected dielectric constants. The nonlinear modified Debye equation (NLMDE) displays a reasonable goodness of fit value for the first five samples. A small polaron hopping mechanism may be responsible for the frequency‐dependent AC conductivity observed in all samples confirming the Jonscher power law. It is discovered that permeability initially increases and then decreases with doping substances. Initial permeability, experimental data from the magnetic hysteresis (M–H) curve, and law‐of‐approach‐to‐saturation techniques show that Ba0.85(Sr0.5Ni0.5)0.15TiO3 and Ba0.75(Sr0.5Ni0.5)0.25TiO3 ceramics have enhanced electromagnetic properties. These ceramics are useful for fabricating electromagnetic sensors.

Gate-driven transition temperatures of electron hopping behaviors in Hubbard bands formed by dopant-induced QD array in silicon nanowire

Abstract Dopant atoms confined in silicon nanoscale channel can be ionized to form quantum dots (QDs). Several dopant atoms couple with each other forming energy bands, where the electron hopping behavior can be described by the Hubbard model. This characteristic renders dopant-induced quantum dots particularly appealing for applications in nanoelectronic and quantum devices. Herein we study the gate-driven transition temperatures of electron hopping behavior in upper and lower Hubbard bands formed by dopant-induced QD array in junctionless silicon nanowire transistors. The gate-dependent transition temperatures are calculated for three stages of electron hopping behaviors including Efros-Shklovskii Variable Range Hopping (ES-VRH), Mott Variable Range Hopping (Mott-VRH) and Nearest Neighbor Hopping (NNH). Our experimental results indicate that the ES-VRH in arrays of dopant atoms occurs in the domination of a long-range Coulomb interaction, in which the hopping distance relies on the Coulomb gap. Furthermore, the localization length of ES-VRH can be modulated by gate voltages.Those factors lead to the significant difference of transition temperatures between the upper and lower Hubbard bands. In addition, we find that the source-drain bias voltage can effectively modulate the transition temperatures between VRH and NNH by thermal activation energies under different bias voltages Vds.

Ultrabroadband and >93% Microwave Absorption Enabled by "Doped" Water Meta-Atom Lattice with Subwavelength Thickness.

Perfect microwave absorbers, which absorb electromagnetic waves completely, play pivotal roles in electromagnetic shielding, and stealth technologies. Existing microwave absorber technologies rely on either electromagnetic properties of absorptive materials, the resonance behavior of meta-atoms, or a combination of both. So far, achieving simultaneous broadband absorption, high efficiency, and compact sizes remains a great challenge. Inspired by atomic doping techniques employed in conventional optical materials to broaden spectral bandwidths, a single-layer microfluidic metasurface microwave absorber is proposed with the assembly of two distinct types of water meta-atoms. By manipulating electromagnetic resonances of these water meta-atoms, the metasurface maintains impedance matching over a broad working range. A microwave absorber design with a thickness equivalent to 0.2 times the central wavelength is showcased, measuring over 93% absorption across both K and Ka bands (17.5-40.0GHz). The results highlight unprecedented superiorities of microwave absorbers based on a 2D doped water meta-atom lattice when compared to previously reported metasurface absorbers utilizing identical meta-atoms. This absorber has advantages including small thickness, broad bandwidth, and cost-effectiveness, making it promising for applications in electromagnetic shielding, camouflage, and multi-spectral stealth.

Theoretical study of point defects on transport properties in metallic interconnections

During the line width reduction, electron scattering caused by various defects in metal interconnects increases dramatically, which causes leakage or short circuit problems in the device, reducing device performance and reliability. Point defects are one of the important factors. Here, using density functional theory and non-equilibrium Green's function methods, we systematically study the effects of point defects on the transport properties of metals Al, Cu, Ag, Ir, Rh, and Ru, namely vacancy defects and interstitial doping of C atom. The results show that the conductivity of all systems decreases compared to perfect systems, because defects cause unnecessary electron scattering. Since the orbital hybridization of the C atom with the Al, Cu and Ag atoms is stronger than that metals Ir, Rh and Ru, the doping of C atom significantly reduces the conductivity of metals Al, Cu and Ag compared to vacancy defects. In contrast, vacancy defects have a greater impact than doping on the transport properties of metals Ir, Rh and Ru, which is mainly attributed to the larger charge transfer of the host atoms around the vacancies caused by lattice distortion. In addition, metal Rh exhibits excellent conductivity in all systems. Therefore, in order to optimize the transport properties of interconnect metals, our work points out that the doping of impurity atoms should be avoided for metals Al, Cu and Ag, while the presence of vacancy defects should be avoided for metals Ir, Rh and Ru, and Rh may be an excellent candidate material for future metal interconnects.

High-throughput screening of the potential alloying elements for high-strength Mg alloys based on solid-solution strengthening

Abstract 49 types of alloy atomic dopants and their effects on the doping stability and micro-mechanical behaviour of magnesium matrix were investigated using density functional theory and high throughput first-principles calculations. Geometry optimization was performed for each doping system, and the ability of atom doping into the magnesium matrix was assessed based on the doping energy and atomic radius. Results show that the transition metal elements have negative or near negative doping energy, especially for the elements with a radius that similar to Mg. The micro-mechanical properties of the doping system were evaluated by computing the fracture energy and theoretical tensile stress. Through a screening on the doping stability and strengthening effect of 49 types of alloy atoms, a set of elements (Re, Os, Ir, Tc and W, etc.) are screened out that could strengthen the magnesium matrix with a good doping stability. The high throughput screen results serve as a theoretical guide for the selection of appropriate alloy elements for designing the high-strength magnesium alloys in the regime of solid solution strengthening effects.

Nitrogen Doping Engineering of V2CTx based Zinc Ion Hybrid Microcapacitors with Quadruple High Energy Density

To accommodate the long-term and stable energy supply requirements for wearable electronics, the reported flexible zinc ion hybrid microcapacitor (ZIHMC) needs to further increase the energy density. So, a nitrogen doped V2CTx (N-V2CTx) based ZIHMC was proposed to achieve high electrochemical performance. The introduction of N heteroatoms by NH3 annealing can dramatically increase the electrical conductivity of V2CTx and simultaneously widen the voltage window to 1.9 V. In detail, the doped nitrogen atoms in V2CTx based device has a maximum capacity of 293.0 mF cm–2, four times higher than that of pure V2CTx based ZIHMC. The mechanism of the enhanced electrochemical performance by nitrogen doped V2CTx was revealed by the experimental analysis and theoretical simulation. And the N-V2CTx based ZIHMC demonstrated high energy density with 150.0 μWh cm–2 at a power density of 380.0 μW cm–2 and excellent stability with 94.80% capacitance retention after 3000 charge-discharge cycles. The N-V2CTx based ZIHMC also presents excellent flexibility without virtually capacity loss after 3000 bending cycles. The good electrochemical performance and flexibility of N-V2CTx ZIHMC make it has potential applications in flexible wearable electronics.

Anion‐Mediated Rapid and Direct Synthesis of FeNiOOH for Robust Water Oxidation

AbstractFeNiOOH is regarded as the most stable active species in the oxygen evolution reaction (OER), but the high oxidation energy of NiOOH poses a challenge to directly synthesize FeNiOOH as a real OER catalyst. Herein, an anion‐mediated kinetically controlled strategy is proposed, coupled with cation‐induced geometric topology modulation, to directly synthesis FeNiOOH with ultra‐thin, densely packed nanosheet architectures. Specifically, the Cl−‐mediated in situ generation of hypochlorous acid promotes the direct formation of NiFeOOH. Concurrently, high‐valence competitive Ru3+ mitigate electrostatic repulsion, fostering a compact and densely packed assembly of Ru/FeNiOOH nanosheet branches. Furthermore, the intrinsic electron‐capturing ability of FeOOH, in synergy with the stabilizing effect of doped Ru atoms, further promote the formation and stabilization high‐valence NiOOH. Consequently, the hierarchical Ru/FeNiOOH@NiPOx nanoarray catalyst displays exceptional OER performance, with an overpotential of 172 mV at 10 mA cm−2 and outstanding stability. This study provides a novel strategy to directly construct a real catalyst.

Static disorder in perovskite-type proton-conducting oxides BaSn1-xMxO3-x/2-(y/2)H2O (M = Ga, Sc, In, Y, La): a novel approach based on statistical analysis of numerous DFT simulated structures.

Perovskite-type proton-conducting oxides inherently include defects such as substitutional aliovalent cations, oxide ion vacancies, and interstitial protons. These defects introduce static disorder into their crystal structures. To investigate such disorder in BaSn1-xMxO3-x/2-(y/2)H2O (M = Ga, Sc, In, Y, La), we employ a novel approach based on density functional theory (DFT) simulations. This approach involves the structural optimization of a large number of relatively small, randomly constructed supercells, followed by statistical analysis of their geometric, energetic, and vibrational properties. Our key findings are as follows. The structural disorder becomes more pronounced as the dopant concentration increases, and as the dopant ionic radius increases from Sc to La. The O-H covalent bond lengths, as well as the number densities, of hydrogen atoms display clearly different distributions depending on whether the hydrogen atoms are trapped by aliovalent cations or not. The hydrogen-trapping energies appear to decrease as the geometric similarity of O-H covalent bonds between trapped and untrapped hydrogen atoms increases. Hydrogen atoms simultaneously trapped by more than one dopant atom exhibit considerable stability, potentially hindering proton diffusion at high dopant concentrations. The O-H stretching wavenumber decreases as the O-H covalent bond length increases, showing a very strong and nearly linear correlation between the two. The simulated IR absorption spectra show semi-quantitative agreement with the measured spectra. These new findings demonstrate the effectiveness of the present 'statistical' approach for investigating static disorder.

Influence of non-metals doping on the structural, electronic, optical, and photocatalytic properties of rutile TiO2 based on density functional theory computations

This study investigates the influence of non-metal doping (C, F, N, and S) on the structural, electronic, and optical properties of rutile TiO2 using Hubbard-corrected density functional theory (DFT) within the Quantum ESPRESSO code. Rutile TiO2 is a promising material for environmental remediation and renewable energy applications. However, it has a large bandgap of 3.03 eV, which confines its use to UV light. By substituting oxygen atoms with a single dopant atom, we aim to shift the absorption edge toward the visible spectrum. Our findings reveal that doping with C, N, and S results in a redshift of the bandgap, while F doping does not exhibit this effect. The imaginary part of the dielectric function indicates shifted absorption edges for C, N, and S-doped TiO2, making them suitable for photocatalytic applications. Additionally, an increased refractive index after doping suggests the presence of excess charge carriers that affect light propagation. This work provides valuable insights for experimentalists exploring non-metal doping influences on rutile TiO2 for photocatalysis.

Twisted Structure Induced Solid-State Fluorescence and Room-Temperature Phosphorescence from Furan-Based Carbon Dots.

Boron doping can effectively induce solid-state fluorescence (SSF) in carbon dots (CDs); however, research on the intrinsic mechanism underlying this phenomenon is lacking. Herein, a design strategy for boron-doped furan-based CDs is proposed, CDs with aggregation-induced emission (AIE) properties are synthesized, and the mechanism by which boron atom dopants induces SSF and room-temperature phosphorescence (RTP) is elucidated. The morphology and structural characterization of the CDs indicate that boron doping leads to structural twisting of the CDs. The AIE phenomenon of CDs arises from the inhibition of the twisted structure motions and a reduction in the nonradiative relaxation rate during the aggregation process. In addition, CDs with twisted structures exhibit a smaller overlap between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO), effectively reducing the singlet-triplet splitting energy (ΔEST). CDs embedded in microcrystalline cellulose (MCC) exhibit green RTP because the nonradiative transitions are suppressed, and the excited triplet species remain stable. For the first time, this study reveals the structure-activity relationship between the twisted structure and optical properties of CDs, providing a new approach for the preparation of solid-state light-emitting CDs.

Architectural Design of a Multichannel Porous Carbon Fiber for Efficient Electromagnetic Microwave Absorption.

An ingenious microstructure of electromagnetic microwave absorption materials is crucial to achieve strong absorption and a broad bandwidth. Herein, one-dimensional (1D) carbon fibers with implantation of zero-dimensional (0D) ZIF-8-derived carbon frameworks and construction of a three-dimensional (3D) microcosmic multichannel porous structure are fabricated by electro-blown spinning, solvent-thermal reaction, and high-temperature pyrolysis techniques. The 1D carbon fiber skeleton with a multichannel structure provides a direct axial conductive pathway for charge transport, which plays an important role in dielectric loss. The 0D surface carbon frameworks offer plenty of heterogeneous interfaces to trigger intensive interfacial polarization loss and act as dihedral angles for microwave scattering. The 3D microcosmic multichannel pores can not only generate multiple reflections as much as possible to dissipate electromagnetic microwave energy but also supply huge interior cavities to improve impedance matching. Thanks to the synergistic effect of a strong electrically conductive pathway for enhancing the conductive loss, a plenteous heterogeneous interface for triggering intensive interfacial polarization loss, microcosmic multichannel pores for generating multiple reflections and improving impedance matching, and N and O atom doping for inducing dipole polarization, the optimal sample with an ingenious microstructure delivers an excellent absorption performance of a minimum reflection loss of -35.5 dB at a thickness of 5.0 mm and an effective absorption bandwidth of 6.72 GHz (10.96-17.68 GHz) at a thickness of 2.0 mm. Such a well-designed multichannel porous carbon fiber may pave the way for the exploitation of high-performance microwave absorbing materials.