Electronic Transport Properties Research Articles

Chalcogen Substitution-Modulated Molecule-Electrode Coupling in Single-Molecule Junctions.

Molecule-electrode interfaces play a pivotal role in defining the electron transport properties of molecular electronic devices. While extensive research has concentrated on optimizing molecule-electrode coupling (MEC) involving electrode materials and molecular anchoring groups, the role of the molecular backbone structure in modulating MEC is equally vital. Additionally, it is known that the incorporation of heteroatoms into the molecular backbone notably influences factors such as energy levels and conductive characteristics. In this work, we report a series of molecular wires that are organized in donor-acceptor-donor configurations, with distinct chalcogen substitutions, including oxygen (BOD), sulfur (BTD), and selenium (BSD). We investigated the electron transport properties using the scanning tunneling microscope break junction (STM-BJ) technique. Our results revealed that both the single-molecule conductance and the junction evolution feature are impacted by the heteroatoms in the benzo(chalcogen)diazole cores. Furthermore, current-voltage (I-V) experiments, combined with theoretical analyses, suggest that MEC plays a dominant role in modulating electron transport behaviors. Overall, our findings provide important insights into the interface-mediated charge transport exerted by chalcogen atoms within molecular devices, thereby enhancing the fundamental comprehension of these critical interactions.

Detection and distinction of amino acids and post-translational modifications with gold nanojunctions.

Amino acids are fundamental building blocks of proteins, playing critical roles in medical diagnostics, environmental monitoring, and biomarker identification. The development of nanoscale electronic sensors capable of single-amino-acid recognition has gained significant attention due to their potential for label-free, real-time detection. In this study, we investigate the electronic transport properties of amino acids in two gold-based nanodevices with distinct architectures: a gold nanojunction and a gold-capacitor system. Using density functional theory (DFT) in combination with nonequilibrium Green's function (NEGF) calculations, we explore the sensing mechanism and conductance variations induced by different amino acids, including select phosphorylated variants. Each device was assigned a reference amino acid, F (M), for a capacitor (nanojunction) to differentiate its conductance from other molecules. Our results reveal distinct conductance that enables amino acid classification based on their electronic signatures, demonstrating that molecular discrimination is primarily governed by conductance variations as a function of the binding energy differences. The nanojunction exhibited remarkable differentiation for the amino acids S, pS, Y, and pY, rendering it especially proficient in distinguishing between structurally analogous molecules. These findings highlight the strong potential of gold-based nanodevices for precise amino acid detection, paving the way for advancements in biosensing technologies, molecular diagnostics, and biomedical applications.

Electromechanics of the Molecule-Electrode Interface and Interface-Mediated Effects in Single-Molecule Junctions.

The molecule-electrode interface can regulate both the efficiency and pathways of electron transport through single-molecule junctions (SMJs). The electromechanics of the interface has proven crucial in exposing the underlying mechanisms of electron transmission through SMJs, providing a theoretical base and practical guidance for designing and constructing functional molecular devices. Here we encompass several currently developed methodologies for investigating the electromechanics of molecule-electrode interface and provide an account of their application in elucidating the effects of the molecule-electrode interface on electron transport properties of SMJs. This review will offer a comprehensive picture and new insights into developing single-molecule electromechanical devices and the progression of devices' mechanical stability toward large-scale integration.

Lattice defect engineering advances n-type PbSe thermoelectrics

Te-free thermoelectrics have garnered significant interest due to their immense thermoelectric potential and low cost. However, most Te-free thermoelectrics have relatively low performance because of the strong electrical and thermal transport conflicts and unsatisfactory compatibility of interfaces between device materials. Here, we develop lattice defect engineering through Cu doping to realize a record-high figure of merit of ~1.9 in n-type polycrystalline PbSe. Detailed micro/nanostructural characterizations and first-principles calculations demonstrate that Cu-induced interstitial defects and nanoprecipitates simultaneously optimize electron and phonon transport properties. Moreover, a robust Co/PbSe interface is designed to effectively prevent chemical reactions/diffusion; this interface exhibited a low electrical contact resistivity of ~10.9 μΩ cm2, excellent durability, and good stability in the thermoelectric module, which achieves a record-high conversion efficiency of 13.1% at a temperature difference of 460 K in segmented thermoelectric modules. This study lays the groundwork for advancing the development of Te-free selenide-based thermoelectric materials.

Correlation Between Conductivity and Oxygen Evolution Reaction Activity in Perovskite Oxides CaMnO3-δ, Ca0.5Sr0.5MnO3-δ and SrMnO3-δ

The perovskite oxides CaMnO3-δ, Ca0.5Sr0.5MnO3-δ, and SrMnO3-δ were synthesized in air using a solid-state method, and their structural, electrical, and electrocatalytic properties were studied in relation to their oxygen evolution reaction (OER) performance. Iodometric titration showed δ values of 0.05, 0.05, and 0.0, respectively, indicating that Mn is predominantly in the 4+ oxidation state across all materials, consistent with prior reports. Detailed characterization was performed using X-ray diffraction (XRD), scanning electron microscopy (SEM), iodometric titration, and variable-temperature conductivity measurements. Four-point probe DC measurements revealed that CaMnO3-δ (δ = 0.05) has a semiconductive behavior over a temperature range from 25 °C to 300 °C, with its highest conductivity attributed to polaron activity. Cyclic voltammetry (CV) in 0.1 M KOH was employed to assess OER catalytic performance, which correlated with room-temperature conductivity. CaMnO3-δ exhibited superior catalytic activity, followed by Ca0.5Sr0.5MnO3-δ and SrMnO3-δ, demonstrating that increased conductivity enhances OER performance. The conductivity trend, CaMnO3-δ > Ca0.5Sr0.5MnO3-δ > SrMnO3-δ, aligns with OER activity, underscoring a direct link between electronic transport properties and catalytic efficiency within this series.

Tuning electronic structure and carrier transport properties through crystal orientation control in two-dimensional Dion-Jacobson phase perovskites

Two-dimensional halide perovskites are attracting attention due to their structural diversity, improved stability, and enhanced quantum efficiency compared to their three-dimensional counterparts. In particular, Dion-Jacobson (DJ) phase perovskites exhibit superior structural stability compared to Ruddlesden-Popper phase perovskites. The inherent quantum well structure of layered perovskites leads to highly anisotropic charge transport and optical properties. Therefore, controlling the preferred crystal orientation (parallel or perpendicular) is crucial for optimizing device performance. This work presents a rational strategy to control parallel and perpendicular crystal growth in C6N2H16PbI4 (4AMPPbI4)-based DJ phase perovskite thin films. We demonstrate that crystal orientation depends on crystal growth rates, which can be controlled by varying the solvent composition, antisolvent, and annealing temperature. Direct and inverse photoelectron spectroscopy reveals that the electronic structure of 4AMPPbI4, including its work function, ionization energy, and electron affinity, is orientation-dependent. Different orientations significantly affect carrier transport as confirmed by single-carrier devices. This study highlights the critical role of crystal orientation in DJ phase perovskites for designing high-performance optoelectronic devices.Graphical

Significant negative differential resistance and current limiting effects of cyclo[14]carbon-based molecular devices with graphene electrodes

Through tip-induced dehalogenation and retro-Bergman ring-opening reaction of fully chlorinated anthanthrene (C14Cl10), the cyclo[14]carbon (C14) was prepared. Owing to its distinctive physical properties, C14 holds the potential to serve as the core unit of functional electronic devices. Herein, the density functional theory combined with the non-equilibrium Green's function technique was used to investigate the electronic transport properties of molecular devices composed of C14 molecules and graphene electrodes, systematically. We find that molecular devices composed of polyynic and cumulenic structures of C14 exhibit a significant negative differential resistance effect and effective current limiting ability at low bias voltages, respectively. Moreover, by calculating and analyzing the transmission function and projected density of states under different biases, a reasonable explanation of those effects is provided.

Commercial SiO Encapsulated in Hybrid Bilayer Conductive Skeleton as Stable Anode Coupling Chemical Prelithiation for Lithium-Ion Batteries.

Although Silicon monoxide (SiO) is regarded as the most promising next-generation anode material, the large volume expansion, poor conductivity, and low initial Coulombic efficiency (ICE) severely hamper its commercialization application. Designing a multilayer conductive skeleton combined with advanced prelithiation technology is considered an effective approach to address these problems. Herein, a reliable strategy is proposed that utilizes MXene and carbon nanotube (CNT)as dual-conductive skeletons to encapsulate SiO through simple electrostatic interaction for high-performance anodes in LIBs, while also performing chemical prelithiation. Various characterizations and electrochemical measurements indicate that both MXene and CNT, as conductive networks and buffer interfaces, synergistically enhance the electron transport and lithium storage properties of the electrode. Moreover, the chemical prelithiation process effectively improves the ICE and cycling stability. Consequently, the prepared SiO@MXene@CNT anode delivers a high capacity of 1032 mAh g-1 after 200 cycles at 200mA g-1 and an ultrahigh capacity retention rate of 89.5% beyond 1000 cycles at 1000mA g-1. More importantly, the ICE of the SiO@MXene@CNT anode increases from 65.1% to 92.3% after chemical prelithiation. The work opens a new avenue for significantly improving the lithium storage performance of SiO-based anodes and is expected to promote their commercialization progress.

Layered double hydroxide modified bismuth vanadate as an efficient photoanode for enhancing photoelectrochemical water splitting.

Photoelectrochemical (PEC) water splitting has attracted significant interest as a promising approach for producing clean and sustainable hydrogen fuel. An efficient photoanode is critical for enhancing PEC water splitting. Bismuth vanadate (BiVO4) is a widely recognized photoanode for PEC applications due to its visible light absorption, suitable valence band position for water oxidation, and outstanding potential for modifications. Nevertheless, sluggish water oxidation rates, severe charge recombination, limited hole diffusion length, and inadequate electron transport properties restrict the PEC performance of BiVO4. To surmount these constraints, incorporating layered double hydroxides (LDHs) onto BiVO4 photoanodes has emerged as a promising approach for enhancing the performance. Herein, the latest advancements in employing LDHs to decorate BiVO4 photoanodes for enhancing PEC water splitting have been thoroughly studied and outlined. Initially, the fundamental principles of PEC water splitting and the roles of LDHs are summarized. Secondly, it covers the development of different composite structures, including BiVO4 combined with bimetallic and trimetallic LDHs, as well as other BiVO4-based composites such as BiVO4/metal oxide, metal sulfide, and various charge transport layers integrated with LDHs. Additionally, LDH composites incorporating materials like graphene, carbon dots, quantum dots, single-atom catalysts, and techniques for surface engineering and LDH exfoliation with BiVO4 are discussed. The research analyzes the design principles of these composites, with a specific focus on how LDHs enhance the performance of BiVO4 by increasing the efficiency and stability through synergistic effects. Finally, challenges and perspectives in future research toward developing efficient and stable BiVO4/LDHs photoelectrodes for PEC water splitting are described.

Multifunctional Native Defects Boosting the Thermoelectric Transport in Few‐Layer PdPS

AbstractAs a unique Cairo pentagonal 2D material, palladium phosphide sulfide (PdPS) has garnered immense interests due to its excellent optoelectronic properties, anisotropic electronic transport behavior, and good air‐stability. In addition, its puckered pentagon structure renders an ultralow thermal conductivity, making it a promising candidate for thermoelectrics applications. However, its thermoelectric transport has not been studied until now due to challenges in obtaining the atomic thin PdPS flake and further measurement. In this work, the thermoelectric performance of 2D PdPS is investigated. It is found that thermoelectric property of PdPS can be effectively manipulated via the delicate annealing treatment, which effectively regulate the defect concentrations. Remarkably, beyond regulating carrier concentrations and shifting the Fermi level closer to the conduction band, these defects also produce a large number of defect states. Consequently, ultra‐high power factor of 0.648 mW m−1 K−2 at room temperature is achieved, outperfoming other 2D materials reported to date. Furthermore, the anisotropic electronic transport properties of few‐layer PdPS are further studied and an extremely high electron anisotropic ratio of 47.37 are obtained at 20 K. The findings provide a new pathway for the development of nanoelectronic devices based on emerging 2D materials with high electronic anisotropy and thermoelectric performance.

A multi-state supramolecular switch realized via a [π⋯π] dimer.

Supramolecular assemblies have attracted great attention in the latest studies of molecular electronic devices for their superiorities. Here, we design a non-covalent [π⋯π] dimer made of DCV4Ts (two-terminally dicyanovinyl-substituted quaterthiophenes), and five typical conformations of this dimer are specifically focused on. Based on density-functional theory calculations and the non-equilibrium Green's function technique, electron transport properties through the dimer are mainly investigated in molecular junctions. It is revealed that four distinct states of conductance can be observed through these five conformations, with the maximal ON/OFF ratio over 400 and the minimal one around 10. The multiple states of conductance basically stem from the destructive quantum interference and the spatial overlap of the two DCV4T monomers. To implement the above-indicated molecular switch in experiments, it is essential to mechanically stretch or compress the designed dimer, probably using the piezo-modulated scanning tunneling microscope based break-junction technique.

Phenyl- versus cyclohexyl-terminated substituents: comparative study on aggregated structures and electron-transport properties in n-type organic semiconductors

This paper reports that specific attractive intermolecular interactions between side-chain substituents can be useful for enhancing charge-carrier mobility in organic semiconductors owing to the suppression of molecular motions.

Effect of defects on ballistic transport in a bilayer SnS2-based junction with Co intercalated electrodes.

This study theoretically investigates the defect-related electronic structure and transport properties in a device where a semiconductor bilayer SnS2 (BL-SnS2) serves as the central scattering region and bilayer SnS2 with cobalt atom intercalation (Co-SnS2) as the metallic electrodes. The Co-SnS2/BL-SnS2 junction forms an ohmic contact, which is robust to defects. Low contact resistances of 52.1 Ω μm and 56.2 Ω μm are obtained in the zigzag (ZZ) and armchair (AC) transport directions, respectively. Defects, whether near the interface or in the middle of the central region, reduce the barrier between metal and semiconductor and the contact resistance. In particular, defects in the middle of the central region introduce impurity states and may result in resonant tunneling processes. This causes leakage current in the AC direction but not in the ZZ direction because impurity-associated transmission peaks in the latter are always outside the bias window.

Low contact resistance in carbon nanotube devices: metal-induced gap states.

Designing devices with low contact resistance, especially those based on carbon-based materials, is becoming increasingly important. In this work, we investigated the electronic structure and transport properties of two-types of structures based on carbon nanotubes connecting graphene electrodes by combining density functional theory with the non-equilibrium Green's function method. The directly connected structure exhibits ohmic contact and has a lower contact resistance compared to the typical van der Waals-connected structure. Furthermore, a metal-induced gap state in the directly connected structure provides an extra transport channel, making electron travel easier. The two structures have around a 4-order-of-magnitude difference in conductance at equilibrium and a 5-order-of-magnitude difference in contact resistance at a bias voltage of 0.4 V. This work may offer basic predictions for carbon nanotube transport as well as novel concepts for designing carbon nanotube transistors.

The effect of acceptor and donor doping on the electronic properties of the half-Heusler TiNiSn.

Optimizing the electronic transport properties of thermoelectric compounds is commonly achieved by either donor or acceptor atom doping to increase the conduction of the appropriate carrier type, electrons or holes, respectively. Enhancing carrier mobility and carrier concentration will both lead to optimized electronic properties. In this work the effect of various dopants on the electronic properties of TiNiSn was explored, by modeling the doping of an ideal compound on the Ti-sublattice with acceptor or donor elements. Using ab initio DFT calculations and a set of analytical expressions of transport properties, the temperature dependencies of the electronic properties were calculated, to examine possible n-type or p-type dopants to be used in further experimental studies.

Analysis of the high-temperature transport property in GaN-based single and double heterostructures

GaN-based heterostructures have been proved to be excellent candidates for high-voltage, large-power, high-frequency and high-temperature application fields, thanks to their superior material properties. To further improve the carriers’ confinement, using InGaN channel layer or introducing AlGaN back barrier layer is promoted. These structures are also proved to be favorable for the robust electron mobility at high temperature. However, the reason solely rests on the longitudinal optical (LO) phonon scattering and the behind mechanism is still absent. This work compares the temperature-dependent electronic transport properties in three groups of GaN-based heterostructures, including GaN-based single heterostructure (SH) with/without AlN interlayer, GaN-based SH and double heterostructure (DH), and GaN-based DH with AlGaN or GaN channel layer. The advantageous high-temperature mobility is attributed to the enhanced LO phonon energy in heterostructures. By self-consistent calculations of the Schrödinger–Poisson equations, a close relation between the narrow electron distribution in the quantum well with the high LO phonon energy, and consequently superior mobility at high temperature is implied. The results provide a simple strategy for the optimized design of the GaN-based heterostructures outperforming at high temperature.

Abnormal Electronic Transport Properties with Hall Effect, Magneto-resistivity, and Phase Diagram in CaFeAsF Single Crystal

Iron-based superconductor 1111-system contains rich physical properties, which can provide a very good material platform for the study of superconducting properties. Recently, it has been found that the annealed CaFeAsF...

Unlocking the mechanical, thermodynamic and thermoelectric properties of NaSbS2: A DFT scheme.

The present study focuses on the ground state mechanical, acoustic, thermodynamic and electronic transport properties of NaSbS2 polymorphs using the density functional theory (DFT) and semi-classical Boltzmann transport theory. The mechanical stability of the polymorphs is affirmed by the calculated elastic tensor. The calculated elastic properties asserted that all the polymorphs exhibit soft, brittle, anisotropic nature containing dominant covalent bonding. The 2D polar graphs are used to describe the anisotropic characteristic of the elastic parameters. The estimated value of Young's modulus and lattice thermal conductivity suggested that the polymorphs could be suitable for thermal barrier coating. Heat capacity, melting temperature, thermal conductivities, Grüneisen parameter, and thermal expansion coefficient of the polymorphs have also been studied to demonstrate thermodynamic behavior. The predicted lower values of lattice thermal conductivity declared that NaSbS2 polymorphs exhibit excellent electrical conductivity and transport properties. The estimated Seebeck coefficient (S), power factor (PF) and figure of merit (ZT) suggested that n-type triclinic and monoclinic, as well as p-type trigonal NaSbS2, are better for thermoelectric applications. The optimal carrier concentration for monoclinic structure is 1021cm-3 for T<750K, while it becomes 1020cm-3 for T>750K. It is also found that the optimal carrier concentration of the trigonal is 1021cm-3, whereas it is 1020cm-3 for triclinic structures. Therefore, it can be stated that NaSbS2 polymorphs possess excellent thermoelectric features, making them a promising choice for thermoelectric (TE) applications.

Computational modeling of triangular γ-graphyne using advanced topological methods

Modeling and computation of molecular descriptors play a crucial role in understanding the properties and characteristics of novel materials like [Formula: see text]-graphyne, the next-generation wonder material. Triangular [Formula: see text]-graphyne is an intriguing two-dimensional carbon-based material with diverse potential applications due to its unique electronic, mechanical, and thermal properties. Triangular [Formula: see text]-graphyne, a distinctive form of carbon allotrope, has garnered substantial interest as a result of its extraordinary characteristics. The notable value lies in its ability to be utilized in diverse domains for potential applications. The interconnected mesh structure of Triangular [Formula: see text]-graphyne exhibits exceptional mechanical strength and exceptional electron-transporting properties. This makes it a promising material for the development of high-performance electronic devices, such as transistors and sensors. Furthermore, gamma graphyne possesses excellent thermal stability, which makes it suitable for applications in the field of energy storage and conversion. It has the potential to be used as a catalyst in fuel cells or as an electrode material in supercapacitors. In this study, we utilize graph theory to dissect the molecular structure of triangular [Formula: see text]-graphyne, leading to the derivation of specific mathematical formulas for essential degree-based molecular characteristics. These findings can be instrumental in examining the correlations between the structure and properties of [Formula: see text]-graphyne. This paper focuses on two structures made from hexagonal honeycomb graphite lattices, like triangular [Formula: see text]-graphyne and triangular [Formula: see text]-graphyne chains with respect to some degree-based topological indices. The results obtained will aid in the investigation of the structure-property relationships in [Formula: see text]-graphyne.

A sandwich-type electrochemiluminescence biosensor based on Ni3(HAB)2/Au@ZnNiAl-LDH/Ru@MIL-53(Al)-NH2 for ultra-sensitive detection of microRNA-155.

Anovel electrochemiluminescence (ECL) biosensor was developed for the ultrasensitive detection of miRNA-155, based on the synergistic combination of multifunctional nanomaterials. The biosensor employed a conductive metal-organic framework (MOF), Ni3(HAB)2 (HAB = hexaaminobenzene), as the substrate material. The unique π-electron conjugated structure of Ni3(HAB)2 endowed the biosensor with excellent electron transport properties, significantly enhancing its sensitivity. Furthermore, the innovative preparation ofAu@ZnNiAl-LDH nanocomposites, characterized by a high specific surface area was employed to synergistically enhance the catalytic performance of the biosensor in conjunction with Ni3(HAB)2.The Au@ZnNiAl-LDH also provided stable anchoring sites for the capture unit, comprised of a DNA tetrahedron hairpin composite structure (DT-HP). Additionally, a porous aluminum-based metal-organic framework (MIL-53(Al)-NH2) was utilized to encapsulate Ru(bpy)32+, constructing a Ru@MIL-53(Al)-NH2 signal unit that effectively improved the stability of the ECL signal. Under optimal conditions, the ECL intensity of the biosensor exhibited a robust linear relationship with the logarithm of miRNA-155 concentration over a range 3 fM to 1nM, achieving a detection limit as low as 0.9 fM. Moreover, the biosensor demonstrated exceptional specificity, selectivity, and stability, highlighting its significant potential for applications in bioanalysis and clinical diagnosis, particularly for the early diagnosis of tumor.