Electronic Characteristics Research Articles

The Model and Simulation of Memristor

Memristor is an emerging electronic component, tremendous efforts have been made in the fields of memristor, motivated by its unique resistor switching feature, as well as the good compatibility with the current integrated circuit (IC) technologies. It has been widely accepted that memristor would be a powerful candidate for constructing the brain-like computing hardware system in the next generation of electronics. Even so, there are still challenges in the development of the memristor IC and the calculation system based on it. For an example, the lack of memristor simulation module hinders its automatic design. Herein, we would like to propose a method for simulating the feature of the memristor. Firstly, based on the conductive filament based physical principle of memristor, calculations are conducted to simulate the basic electronic features of memristor. The good fitness confirms the feasibility of the proposed method. Second, the memristor’s resistance switching feature is modelled by Spice, a popular design platform. With the use of Voltage-Controlled Current Source (VCCS) in Spice, a modulus of memristor is established and executed to simulate the switched resistances under different bias voltages. In summary, this work demonstrates the feasibility of the proposed simulating method, it may provide an easy-to-operate way to improve design efficiency of active memristor arrays

Nucleation, Electronic, and Optical Properties of Bi Thin Films Electrodeposited on n‐Si(111) Substrate

This study investigates the electrochemical nucleation and growth mechanisms of bismuth on a monocrystalline n‐Si(111) substrate from an acidic nitrate solution. It also examines the electrical and optical properties of the electroplated films. The qualitative analysis of the experimental current transients reveals a strong agreement with instantaneous nucleation on active sites and three‐dimensional diffusion‐controlled growth. Electrochemical kinetic parameters are derived using the Mirkin–Nilov–Heerman–Tarallo model, which is employed to fit the experimental curves. Electrochemical impedance spectroscopy and Mott–Schottky analysis are used to assess the electronic characteristics of the materials. Scanning electron microscope observations show a uniform, smooth, and continuous deposit. X‐ray diffraction analysis indicates a high texture along the [012] direction of the rhombohedral crystal structure in thin bismuth films with different thicknesses (118, 318, and 611 nm). UV–visible spectroscopy is employed to investigate the optical characteristics of the Bi/Si surface in the 200–1100 nm wavelength range. The study demonstrates that the thickness of the bismuth film affects the absorption response of the Bi/Si heterojunction, showing a notable increase in absorption in the visible and infrared ranges. Furthermore, it is found that the photoluminescence properties of the Bi/Si heterojunction are improved in the visible and infrared ranges.

Enantiomerically Pure Helical Bilayer Nanographenes: A Straightforward Chemical Approach.

The semiconductor properties of nanosized graphene fragments, known as molecular nanographenes, position them as exceptional candidates for next-generation optoelectronics. In addition to their remarkable optical and electronic features, chiral nanographenes exhibit high dissymmetry factors in circular dichroism and circularly polarized luminescence measurements. However, the synthesis of enantiomerically pure nanographenes remains a significant challenge. Typically, these materials are synthesized in their racemic form, followed by separation of the enantiomers using high-performance liquid chromatography (HPLC). While effective, this method often requires expensive instrumentation, extensive optimization of separation conditions, and typically yields analytical quantities of the desired samples. An alternative approach is the enantioselective synthesis of chiral molecular nanographenes; however, to date, only two examples have been documented in the literature. In this work, we present a straightforward chemical method for the chiral resolution of helical bilayer nanographenes. This approach enables the effective and scalable preparation of enantiomerically pure nanographenes while avoiding the need for HPLC. The incorporation of a BINOL core into the polyarene precursor facilitates the separation of diastereomers through esterification with enantiomerically pure camphorsulfonyl chloride. Following the separation of the diastereomers by standard chromatographic column, the hydrolysis of the camphorsulfonyl group yields enantiomerically pure nanographene precursors. The subsequent graphitization, achieved through the Scholl reaction, occurs in an enantiospecific manner and with the concomitant formation of a furan ring and a heterohelicene moiety. The absolute configurations of the final enantiomers, P-oxa[9]HBNG and M-oxa[9]HBNG, have been determined using X-ray diffraction. Additionally, electrochemical, photophysical, and chiroptical properties have been thoroughly evaluated.

Electronic Nature and Thermoelectric Characteristics of Cubic LaPb3 LaIn3 and LaTl3 Compounds: B3PW91 Approach

In this paper the structural, electronic and transport properties of the strongly correlated intermetallics LaX3 (X=Pb, In and Tl) in the space group Pm-3m (221) have been investigated using B3PW91 hybrid functional within the framework of density functional theory. These compounds have 4f orbitals and hence strong electron-electron correlation effect is expected, therefore, the electronic properties are also calculated with the B3PW91 hybrid functional and the effect of B3PW91 hybrid functional on the density of states is discussed in details. The band structure and density of states, demonstrate the metallic nature of these compounds. Using the semi-empirical Boltzmann’s approach implemented in the BoltzTraP code, the transport parameters, such as the Seebeck coefficient, electrical conductivity, thermal conductivity and figure of merit as a function of the chemical potential are computed at a temperature gradient of 500 K. For all materials the thermal and electrical conductivities, and Seebeck coefficient has higher values for n-type doping in comparison with p-type doping. The moderate values of figure of merit obtained for these materials indicate that these materials have applicability where small values of thermoelectric efficiency are required and higher values can harm the process but need experimental verification. LaIn3 has the highest value of electrical conductivity per relaxation time and thermal conductivity per relaxation time are 9.43 x 1020 1/Ωms and 107.65 x 1014 W/mKs respectively. LaTl3 has the highest figure of merit among these materials.

Self-assembly of 1T/1H superlattices in transition metal dichalcogenides

Heterostructures and superlattices composed of layered transition metal dichalcogenides (TMDs), celebrated for their superior emergent properties over individual components, offer significant promise for the development of multifunctional electronic devices. However, conventional fabrication techniques for these structures depend on layer-by-layer artificial construction and are hindered by their complexity and inefficiency. Herein, we introduce a universal strategy for the automated synthesis of TMD superlattice single crystals through self-assembly, exemplified by the NbSe2-xTex 1T/1H superlattice. The core principle of this strategy is to balance the formation energies of T (octahedral) and H (trigonal prismatic) phases. By adjusting the Te to Se stoichiometric ratio in NbSe2-xTex, we reduce the formation energy disparity between the T and H phases, enabling the self-assembly of 1T and 1H layers into a 1T/1H superlattice. The resulting 1T/1H superlattices retain electronic characteristics of both 1T and 1H layers. We further validate the universality of this strategy by achieving 1T/1H superlattices through substituting Nb atoms in NbSe2 with V or Ti atoms. This self-assembly for superlattice crystal synthesis approach could extend to other layered materials, opening new avenues for efficient fabrication and broad applications of superlattices.

Two-Dimensional Rare-Earth Metal Phosphides: From Weyl Semimetal to Semiconductor.

Two-dimensional (2D) nanomaterials have garnered extensive attention owing to their unique properties and versatile application. Here, a family of 2D rare-earth metal phosphides (M2P, M = Sc, Y, La) and their derivatives M2POT (T = F, OH) is developed to find their topological and electronic properties on the basis of density functional theory simulations. We show that the 2D M2P compounds are most possibly obtained from thermodynamically stable M2InP by chemical exfoliation. The In with a substantial atomic radius of 156 pm exhibits weak polarization ability, resulting in homogeneity of the electron cloud and a weakening of the M-In bond relative to the M-P bond. Upon exfoliation of the In layer, the M22+P3-:e- emerges as an electride with surface electrons, which is attributed to the larger ion radius and lower electronegativity of M2+ ions in M2P. The metallic M2P is found to be a Weyl semimetal derived from the contribution of surface electrons. Further, by leveraging the high reactivity of surface electrons, surface functionalization can produce M2POT compounds with the increased valence state of M3+, which results in their semiconducting properties characterized by high carrier mobilities and strong built-in electronic fields. These distinct topological and electronic characteristics position the 2D M2P and M2POT as promising candidates for a wide range of applications.

First-principles investigation of oxygen repulsion behavior on the Ir–Hf alloy surface

Enhancing the oxidation resistance of hot-end components under extreme conditions is a key focus in aerospace equipment research. We used first-principles simulations to investigate a series of IrxHf100−x (at. %) coatings. By employing density functional theory and the local density approximation method, we studied the surface oxygen repulsion energy and estimated the optimal composition ratio of IrxHf100−x for the strongest oxidation resistance. The results indicate that as the Hf content increases, the oxygen repulsion energy first rises and then falls, reaching a maximum value of 3.04 eV at x = 10 at. %, with active oxygen adsorption occurring when X exceeds 45 at.%. To understand the mechanism of the oxygen repulsion process, we analyzed the electronic characteristics between Ir, Hf, and O. O preferentially hybridizes its atomic orbitals with Ir, and the improvement in oxidation resistance of the Ir–Hf coating is attributed to the reduction in Ir atomic spacing due to Hf doping, which reduces O–Ir orbital hybridization.

Sc2CX2(X=O, S, Se) 2D-MXene materials for thermoelectric applications: A DFT study

MXene Sc2CX2(X = O, S, Se) have band gap tunability and are environmentally neutral, making them useful for future studies. In this current manuscript, we have theoretically investigated the physical traits of Sc2CX2(X = O, S, Se) using the FP-LAPW technique embedded in Wien2K simulations. These compounds exhibit thermodynamically, and structural stability confirmed through volume optimization curves. The electronic characteristics reveal indirect band gaps of these materials. The ultraviolet area is where materials absorb most light, indicating their potential for use in UV based optoelectronic devices. The transport traits examined depict the high PF values which demonstrate the importance of these compounds for renewable energies.

Investigation of the Physical Attributes of Sr2GeCrO6, Sr2MgMoO6, Ba2MgMoO6, Ba2ZnMoO6, and Ba2HgWO6 Double Perovskite Oxides

A density functional theory‐based study on the physical properties of significant double perovskite oxides Sr2GeCrO6, Sr2MgMoO6, Ba2MgMoO6, Ba2ZnMoO6, and Ba2HgWO6 has been conducted using the Vienna Ab initio Simulation Package and WIEN2K code. Structural analysis reveals the simple cubic crystal structure of double perovskite oxides. Phonon properties indicate the dynamical stability of Sr2GeCrO6, Ba2MgMoO6, and Ba2ZnMoO6 compounds. The band structure analysis indicates the metallic character of Sr2GeCrO6. However, generalized gradient approximation of Perdew–Burke–Ernzerhof and modified Becke–Johnson both suggest the indirect semiconducting nature of Ba2MgMoO6 and Ba2ZnMoO6. The crystal orbital Hamilton population (–COHP) examination evidences the strongest bonding interactions of O–Ba in these perovskite oxides. Both Ba2MgMoO6 and Ba2ZnMoO6 compounds exhibit p‐type character, as indicated by the partial charge density distributions in the highest occupied molecular orbital and lowest unoccupied molecular orbital (LUMO) orbitals, which govern the band edges near Fermi level. LUMO orbitals are located on Mo and O atoms and are composed of heteronuclear s‐ and p‐type interactions. The investigation comprehensively analyzes calculated optoelectronic properties, including complex dielectric function, optical conductivity, loss function, refractive index, and so on. These parameters are examined in detail, offering profound insights into the materials’ optical and electronic characteristics.

Computational screening and investigation of ligand effect on TM single atom catalyst for hydrogen evolution reaction

Here, we studied the stability, electronic characteristics, and HER catalytic performance of a transition metal single atom catalysts, both with and without the presence of chlorine ligand. The findings indicate that all catalysts, except for Au, Au-Cl, Ag, Ag-Cl, are thermodynamically stable. We found 3d transition metals are more stable than those in the 4d and 5d series. Ag-Cl, Sc, Ag, Fe-Cl, and Cr-Cl have the poorest electrochemical stability. We found a negative Pearson correlation between Fermi energy and formation energy for TM-Cl, which is opposite to the trend observed for bare TM catalysts. The higher HER activity of chlorine bonded system for the early 3d TM suggests that the downshifting of the d-band center facilitates the activity. We also observed a periodic trend in the d-band center for both TM and TM-Cl systems. Mn-Cl, Cr-Cl, Ti-Cl, Fe-Cl, V-Cl and Zn emerged as the superior catalysts in our study series.

Grain Boundary Engineering Enhances the Thermoelectric Properties of Y2Te3

AbstractThe performance of thermoelectric materials is typically assessed using the dimensionless figure of merit, zT. Increasing zT is challenging due to the intricate relationships between electrical and thermal transport properties. This study focuses on Y2Te3‐based thermoelectric materials, which are predicted to be promising for high‐temperature applications due to their inherently low lattice thermal conductivity. A series of Y2+xTe3 compositions with excess Y is synthesized to explore the effects on electronic and structural characteristics. Density functional theory calculations suggest that additional Y atoms increase charge carriers, thereby enhancing electrical conductivity and boosting thermoelectric performance. X‐ray diffraction analysis reveals that the presence of excess Y reduces lattice volume and alters bonding structures. Furthermore, the addition of Bi significantly enhances the power factor by promoting the segregation of elemental Bi particles and the formation of Y‐Bi‐rich grain boundaries, which improve weighted mobility. This microstructural optimization leads to a fourfold increase in the Seebeck coefficient, resulting in a peak zT of 1.23 at 973 K and a predicted maximum conversion efficiency of 10.3% under a temperature difference of 673 K. These findings highlight the potential of Y2Te3 for high‐temperature thermoelectric applications and demonstrate the effectiveness of grain boundary engineering in enhancing thermoelectric performance.

Electric field stimulation on electronic, electro-optical and non-linear optical properties of some fluoro-isothiocyanate and fluorinated alkyl terphenyl liquid crystals: A comparative DFT approach

Employing density functional theory, electronic, electro-optical, and NLO properties of some fluorinated NCS terphenyl and fluorinated terphenyl liquid crystals have been investigated in the presence of static electric field. Two DFT functionals, in this study, includes M06-2X and ωB97XD combined with 6–311 + G(d,p) basis set have been used. All the computations have been performed on Gaussian 16 W program and visualized on GaussView6.0. A comparative analysis of computational outcomes has been done in order to forecast mesogens’ improved electronic characteristics, global descriptors, NLO and UV–vis spectra. All of the chosen LC molecules exhibit properties that make them suitable materials for NLO applications.

First principles investigation of double perovskites Li2CuAsZ6 (Z = Cl, Br, I) as a suitable alternatives for energy conversion technologies

The present study employs density functional theory to examine the physical properties of halide double perovskites Li2CuAsZ6 (Z = Cl, Br, I). The stability of the phase has been confirmed by analyzing the cubic layout and the values of the octahedral and tolerance factors. The formation energies of all perovskites have been computed to guarantee thermodynamic stability. The detailed description of the electronic characteristics of Li2CuAsZ6 reveals its behavior as a semiconductor. Energy band gaps of 0.55 eV, 0.33 eV, and 0.088 eV for Li2CuAsCl6, Li2CuAsBr6, and Li2CuAsI6, respectively, are determined by our calculations. Additionally, we have investigated the optical properties of these materials with 0–4 eV energy span in detail, which are reported as strong candidates for use in optoelectronic systems. The BoltzTraP code is employed to evaluate the thermoelectric characteristics. The lower lattice thermal conductivity values for Li2CuAsCl6, Li2CuAsBr6, and Li2CuAsI6 suggest less contribution to thermoelectric functionality. Finally, this discussion indicates the suitability of studied perovskites for energy conversion systems; however, experimental confirmation is necessary before these perovskites may be used in thermoelectric and optoelectronic systems.

Atmosphere-driven oriental regulation of Ru valence for boosting alkaline water electrolysis

Modulating the electronic characteristics of nanomaterials has been key to advancing sustainable energy technologies. In this study, we controlled the Ru electronic properties of NiRuOx by varying the calcination atmospheres (Air and Argon), resulting in two distinct electrocatalysts: NiRuOx-O2 with Ru4+ species and NiRuOx-Ar with Ru0 species as the main component. We established the relationship between the valence of Ru and its HER and OER catalytic activity as NiRuOx for example. Specifically, NiRuOx-Ar with metallic Ru demonstrates better alkaline HER activity with a smaller overpotential (94 mV) at 100 mA cm−2 than NiRuOx-O2 with Ru4+ due to the reduced Ru0 superiority towards H*. Conversely, NiRuOx-O2 shows superior alkaline OER performance with only 275 mV overpotential at 100 mA cm−2 compared with that of NiRuOx-Ar (383 mV) due to Ru4+ receiving electrons from Ni species and reduced Ru–O covalence. The NiRuOx-O2//NiRuOx-Ar electrolyzer in 1 M KOH achieves 10 mA cm−2 at 1.475 V with 100 h durability, surpassing the RuO2//Pt/C cell (1.516 V). Revealing the correlation between Ru valence and activity offers important insights for the rational design of Ru-based catalysts for HER and OER.

Synthesis, Structural Characterization, and Electronic Structure Analysis of F2-type Superatomic Molecules.

The investigation of bonding interactions between superatoms continues to be a largely unexplored area of study. In this study, we present the synthesis and characterization of two F2-type superatomic molecules [Au2Ag25(C7H4NOS)13(DPPB)3] and [Au9Ag18(C5H4NS)11(DPPM)5]2+ (Au2Ag25 and Au9Ag18 for short, respectively). The overall structures were confirmed via X-ray crystallography, revealing the horizontal expansion of the biicosahedral Au2Ag21 yielding [Au2Ag25(C7H4NOS)13(DPPB)3] and vertical expansion of the biicosahedral Au8Ag15 yielding [Au9Ag18(C5H4NS)11(DPPM)5]2+. Furthermore, their electronic structures were elucidated through density functional theory (DFT) calculations. Spectroscopic analysis of electronic absorption characteristics, in conjunction with Tamm-Dancoff approximation DFT (TDA-DFT) calculations, revealed that the Au2Ag21(+9) and Au8Ag15(+9) cores were analogues of the F2 molecule in electronic configuration.

The Reversible Electron Transfer Within Stimuli-Responsive Hydrochromic Supramolecular Material Containing Pyridinium Oxime and Hexacyanoferrate (II) Ions

The structural and electronic features of the stimuli-responsive supramolecular inter-ionic charge-transfer material containing electron accepting N-benzylyridinium-4-oxime cation (BPA4+) and electron donating hexacyanoferrate (II) are reported. The study of reversible stimuli-induced transformation between hydrated reddish-brown (BPA4)4[Fe(CN)6]·10H2O and anhydrous blue (BPA4)4[Fe(CN)6] revealed the origin of observed hydrochromic behavior. The comparison of the crystal structures of decahydrate and anhydrous phase showed that subsequent exclusion/inclusion of lattice water molecules induces structural relocation of one BPA4+ that alter the donor-to-acceptor charge-transfer states, resulting in chromotropism seen as reversible reddish-brown to blue color changes. The decreased donor-acceptor distance in (BPA4)4[Fe(CN)6] enhanced charge-transfer interaction allowing charge separation via one-electron transfer, as evidenced by in-situ ESR and FTIR spectroscopies. The reversibility of hydrochromic behavior was demonstrated by in-situ HT-XRPD, hot-stage microscopic and in situ diffuse-reflectance spectroscopic analyses. The insight into electronic structural features was obtained with density functional theory calculations, employed to elucidate electronic structure for both compounds. The electrical properties of the phases during dehydration process were investigated by temperature-dependent impedance spectroscopy.

The effects of Cobalt doping on the structural, electronic, magnetic, and thermodynamic characteristics of the L10-FeNi alloy: First-principle calculations

This study conducts a computational analysis employing density functional theory (DFT) to investigate the effects of Cobalt doping as substitutional defects on the structural, electronic, magnetic, and thermodynamic characteristics of the L 10− FeNi alloy. The aim of this study was to explore their potential applications as alternatives to rare-earth permanent magnets. Two types of substitutional Co-doping (ONi/OFe) in the Ni/Fe-site of the parent alloy have been investigated. The computed formation energy indicates that the incorporation of cobalt defects increases the structural stability of tetragonally distorted L10FeNi via Co-doping. The results we obtained demonstrate that the FeNi:Co (ONi) in the L10-structure has a large enhancement in magnetic moments and saturation magnetization (Ms), whereas for the FeNi:Co (OFe), has a small reduction in Ms. Furthermore, reducing the concentration of cobalt in L10 FeNi:Co alloys is advantageous in diminishing the volumetric thermal expansion coefficient, consequently lowering the Debye temperature and weakening atom interactions. Therefore, Co-substituted FeNi alloys hold promise as potential candidates for rare-earth-free permanent magnets.

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.

Rational Molecular Design for Balanced Locally Excited and Charge- Transfer Nature for Two-Photon Absorption Phenomenon and Highly Efficient TADF-Based OLEDs.

The pursuit of highly efficient thermally activated delayed fluorescence (TADF) emitters with two-photon absorption (2PA) character is hampered by the concurrent achievement of a small singlet-triplet energy gap (ΔEST) and high photoluminescence quantum yield (ФPL). Here, by introducing a terephthalonitrile unit into a sterically crowded donor-π-donor structure, inducing a hybrid electronic excitation character, we designed unique TADF emitters possessing 2PA ability. This rational molecular design was achieved through a main π-conjugated donor-acceptor-donor backbone in line with locally excited feature renders a large oscillator strength and transition dipole moment, maintaining a high 2PA cross-section value. The ancillary N-donor-acceptor-donor with charge transfer character highly balances the TADF phenomenon by minimizing ΔEST. A near-unity ФPL value with a large radiative decay rate over an order of magnitude higher than the intersystem crossing rate and a high horizontal orientation ratio of 0.95 were simultaneously attained for TPCz2NP. The organic light-emitting diodes fabricated with this material exhibit a high maximum external quantum efficiency of 25.4% with an elevated 2PA cross-section (σ2) value up to 143GM at 850 nm. These findings offer a venue for designing high-performance TADF emitters with exceptional performance inclusive of 2PA properties, expanding for future functional material design.

Rational Molecular Design for Balanced Locally Excited and Charge‐ Transfer Nature for Two‐Photon Absorption Phenomenon and Highly Efficient TADF‐Based OLEDs

The pursuit of highly efficient thermally activated delayed fluorescence (TADF) emitters with two‐photon absorption (2PA) character is hampered by the concurrent achievement of a small singlet‐triplet energy gap (ΔEST) and high photoluminescence quantum yield (ФPL). Here, by introducing a terephthalonitrile unit into a sterically crowded donor‐π‐donor structure, inducing a hybrid electronic excitation character, we designed unique TADF emitters possessing 2PA ability. This rational molecular design was achieved through a main π‐conjugated donor‐acceptor‐donor backbone in line with locally excited feature renders a large oscillator strength and transition dipole moment, maintaining a high 2PA cross‐section value. The ancillary N‐donor‐acceptor‐donor with charge transfer character highly balances the TADF phenomenon by minimizing ΔEST. A near‐unity ФPL value with a large radiative decay rate over an order of magnitude higher than the intersystem crossing rate and a high horizontal orientation ratio of 0.95 were simultaneously attained for TPCz2NP. The organic light‐emitting diodes fabricated with this material exhibit a high maximum external quantum efficiency of 25.4% with an elevated 2PA cross‐section (σ2) value up to 143 GM at 850 nm. These findings offer a venue for designing high‐performance TADF emitters with exceptional performance inclusive of 2PA properties, expanding for future functional material design.