Electronic Transmission Coefficient Research Articles

"V"-Shaped Changing Electronic Performance of Iodinene-Based Nanoflakes as a Function of Width.

Special structures and prominent performance make 2D iodinene more appealing and valuable at the molecular level. Here, new-type electronic devices have been constructed with iodinene-based nanoflakes in different sizes and are theoretically studied for electronic transport properties. Our findings reveal that iodinene-based nanoflakes possess great electron transport suppression, achieving the same function as SiO2 on single molecule scale. Such transport suppression shows surprisingly nonlinear "V"-shaped trend with the width of the iodinene-based nanoflake. The medium-width iodinene-based nanoflake exhibits the strongest electron transport suppression, while the narrowest and widest ones display the largest electron transmission coefficients due to delocalized transmission eigenstates. Essentially, the weakest electron transport originates from an extremely small DOS and wide HOMO-LUMO gap. Specifically, increasing the width would diminish the extension of electronic states for the dominant transport orbitals, resulting in more butterfly-like electronic states. In non-equilibrium, negative differential resistance effect can be observed in iodinene-based devices, caused by the weakening and staying away from the Fermi level of transmission peaks influenced by the bias. Our findings provide insights into the relationship between the width of iodinene-based nanoflake and electronic transport properties, and lay a foundation in the device design and applications in molecular insulators and controllable-functional devices.

Enhancement of electrical and radiation shielding properties of vanadium doped lithium telluro-borate (LTB) glasses

Vanadium doped lithium telluro-borate (LTB) glasses of the composition (20-x)Li2O-20TeO2-60B2O3-(x)V2O5 (x = 0, 0.5, 1, 1.5 and 2 in mol %) were synthesised by melt quenching technique. The structural, optical, physical, electrical and radiation shielding parameters of the prepared glasses were investigated to determine the effect of vanadium in the LTB glass matrix. Density of LTB glasses were found to increases from 2.52 to 2.98 g/cm3 under addition of vanadium oxide and certain density derived structural parameters were studied. XRD pattern confirms the amorphous nature of the pristine and doped LTB glass. FTIR spectra shows the presence of various bonds in the vanadium doped LTB glasses. The direct optical bandgap (Eg) decreases due to the addition of V2O5 and leads to creation of defects in the LTB glasses thereby increasing the Urbach energy (Eu). Physical parameters like refractive index (n), molar refractivity (Rm), reflection loss (Lr), molar electronic polarizability (αm), transmission coefficient (T) and metallization criteria (M) were calculated. The electrical properties including dielectric constant (εʹ), conductivity (σ) and activation energies (Ea) were analysed and observed that Ea decreases under the addition of vanadium to the glass network proving the enhancement in electrical conductivity. Radiation shielding parameters such as MAC, LAC, HVL, TVL, MFP, R, ACS, ECS, Neff, Zeff, and Ceff were calculated using Phy-X/PSD and LTB_2V with the highest V2O5 additive shows enhanced result in gamma radiation shielding.

Structural and optical properties of lithium borate glasses under extreme conditions of ion irradiation

Lithium borate (LBO) glasses of the composition 10LiO2.90B2O3 were prepared by melt quenching technique and characterized for morphological, structural, and optical properties before and after the exposure to the extreme conditions of 100 MeV Ni ion irradiation. Both the morphological images and structural properties confirm the transformation of LBO glasses from amorphous to polycrystalline nature. This Ni irradiation provides thermal energy that causes the ceramization of glass. The beam interacts with the material where the top layer of the glass remelts, and ultrafast re-solidification occurs after the termination of the ion beams. The Rietveld refinement using the x-ray diffraction data shows that the irradiated LBO possesses a monoclinic crystal structure of lithium pentaborate pentahydrate (B5H10LiO13). The FTIR spectra of Ni ion irradiated glasses show the creation of non-bridging oxygens (NBO) by the formation of BO4 units at the expense of BO3 units. The direct band gap and the Urbach energy of the glasses are affected by the nickel ion irradiation and are in the range 2.73 to 2.55 eV and 0.59 to 0.42 eV. The refractive index also reveals a minor change (1.66 to 1.63). The molar electronic polarizability, metallization criteria, and transmission coefficient were estimated. The coexistence of crystalline and amorphous phases leads to a multiscale phase structure that has multilevel relaxation processes. This is a suitable condition for the improvement of the rheological properties of glass and glass ceramics. Future work involves optimization of the coexistence of these two phases during irradiation.

A study of tunneling in triangular resonant tunnel diodes: Effect of barrier width, barrier height, pressure, temperature, and heterostructure strain

Using the transfer matrix, the transmission coefficient of electrons is examined in the triangular double-barrier semiconductor heterostructure. GaAs-based heterostructure is considered to study the role of barrier width, barrier height, pressure and temperature. The geometrical parameters of the heterostructures (barrier width and barrier height) and the external perturbation (pressure and temperature) influence the tunneling properties. The tunneling time of the electrons is also studied using Heisenberg's uncertainty principle. The account of the heterostructure strain is also discussed.

Electronic transport and thermoelectric properties of phosphorene nanodisk under an electric field

The Seebeck coefficient is an important quantity in determining the thermoelectric efficiency of a material. Phosphorene is a two-dimensional material with a puckered structure, which makes its properties anisotropic. In this work, a phosphorene nanodisk (PDisk) with a radius of 3.1 nm connected to two zigzag phosphorene nanoribbons is studied, numerically, by the tight-binding and non-equilibrium Green’s function (NEGF) methods in the presence of transverse and perpendicular electric fields. Our results show that the change in structure from a zigzag ribbon to a disk form creates an energy gap in the structure, such that for a typical nanodisk with a radius of 3.1 nm, the size of the energy gap is 3.88 eV. Besides, with this change, the maximum Seebeck coefficient increases from 1.54 to 2.03 mV/K. Furthermore, we can control the electron transmission and Seebeck coefficients with the help of the electric fields. The numerical results show that with the increase of the electric field, the transmission coefficient decreases and the Seebeck coefficient changes. The effect of a perpendicular electric field on the Seebeck coefficient is weaker than a transverse electric field. For an applied transverse electric field of 0.3 V/nm, the maximum Seebeck coefficient enhances to 2.09 mV/K.

Перенос электронов через границу полупроводник-вакуум с отрицательным и положительным электронным сродством: влияние скачка массы

The effect of jump in electron mass at the crystal-vacuum interface on photoemission from semiconductors is considered. In the effective mass approximation, the angular and energy dependences of the electron transmission coefficient through interfaces with a jump in mass and potential steps of different signs, corresponding to negative and positive electron affinities, are considered. It is shown that due to the jump in mass, there are a critical energy and a critical angle of incidence of electrons, which separate qualitatively different angular and energy dependences of the transmission coefficient, respectively. The jump in mass makes it possible for electrons to transfer (up to complete transmission) through a positive potential step with a normal component of kinetic energy below the height of the step. The calculated dependences of the emission quantum yield of thermalized electrons on the affinity value are compared with the experimental data on photoemission from p-GaAs(Cs,O). Possible reasons for the significant differences between the experiment and the calculation are analyzed: a complex potential profile, including the near-surface band bending in the semiconductor and the image charge potential in vacuum, scattering in the (Cs,O) layer, and the need to go beyond the effective mass approximation and to take into account full Bloch nature of electron wave functions in semiconductors.

Resonant tunneling diodes in semiconductor microcavities: Modeling polaritonic features in the terahertz displacement current

We develop in this work a simple qualitative quantum electron transport model, in the strong light-matter coupling regime under dipole approximation, able to capture polaritonic signatures in the time-dependent electrical current. The effect of the quantized electromagnetic field in the displacement current of a resonant tunneling diode inside an optical cavity is analyzed. The original peaks of the bare electron transmission coefficient split into two new peaks due to the resonant electron-photon interaction, leading to coherent Rabi oscillations among the polaritonic states that are developed in the system in the strong coupling regime. This mimics known effects predicted by a Jaynes-Cummings model in closed systems, and shows how a full quantum treatment of electrons and electromagnetic fields may open interesting paths for engineering new THz electron devices. The computational burden involved in the multi-time measurements of THz currents is tackled by invoking a Bohmian description of the light-matter interaction. We also show that the traditional static transmission coefficient used to characterize DC quantum electron devices has to be substituted by a new displacement current coefficient in high-frequency AC scenarios.

The resonant condition of transmission in the graphene-based double-barrier structures

The Klein tunneling of Dirac fermions through a symmetric double potential barrier of a rectangular shape in graphene has been investigated. A new analytical formula for a dependence of the transmission coefficient of electrons on the angle of incidence on the barrier was obtained, on the basis of which the conditions for the angles of incidence with 100% transmission were found. In the case of a double potential barrier we have three conditions for resonance tunneling, two of which are similar to those conditions for one barrier, and the third one reflects the presence of the second barrier.

Stability and electronic transport properties for discernible binary (BN)Cx armchair heteronanotubes

We study the electronic transport properties in the (BN) Cx armchair heteronanotubes with binary supercells. The binary supercell consists of a junction of two single (BN) Cx supercells either as the conventional double period structure or two following discernible BN-C patterns. We consider three kinds of discernible binary supercells according to the different orientations of the separated BN armchair cells in both longitudinal and circular directions inside the armchair nanotube. Contrary to the perfect double period structure, the discernible binary (BN)Cx armchair heteronanotube behaves either as a semiconductor or a metal, according to the resulted backscattering effects inside the binary supercell. Moreover, by combining the resulted electronic band structure with the electronic transmission coefficient of the incorporated binary supercell between two perfect leads of carbon nanotubes, we report three universal types of the backscattering effects as fingerprints of the corresponding binary supercell. These types evolve with different regular sequences when the number 'x' of the armchair carbon cells increases inside each kind of the binary (BN) Cx supercell. The energetic stability parameters have also been checked for the BN circular orientations. No evidence for a privileged circular phase has been recorded for the binary (BN)Cx heteronanotubes. The calculations have been performed based on the density functional tight-binding model as implemented in the DFTB ​+ ​software package.

Electronic transport properties of a-Si:H

To investigate the electron transport properties of hydrogenated amorphous silicon (a-Si:H), a series of quantum simulations and electron transport analyses were performed. The target system is a nano-scale junction of a-Si:H with various hydrogen concentrations sandwiched between two metal electrodes. The density functional based tight binding simulation was conducted to obtain the electronic structure, and the non-equilibrium Green’s function method was adopted to evaluate the electron transmission coefficient and the electric current under a bias field. It is confirmed that the hydrogen atoms passivate a part of defects in amorphous silicon, but the remaining defects realize the energy states in the bandgap; the p orbitals of silicon atoms mainly contribute to the electron transmission. The transport behavior is greatly affected by the hydrogen concentration. The interface between a-Si:H and the metal electrodes also influences the transport behavior through changing the spatial charge density inside the a-Si:H.

Unexpected role of electronic coupling between host redox centers in transport kinetics of lithium ions in olivine phosphate materials.

The discrepancy between the trend in the diffusion coefficient of a lithium ion (DLi+) and that in the activation energy of ion hopping signals hidden factors determining ion transport kinetics in layered olivine phosphate materials (LiMPO4). Combining density functional theory (DFT) calculations and the Landau–Zener electron transfer theory, we unravel this hidden factor to be the electronic coupling between redox centers of the host materials. The ion transport process in LiMPO4 is newly described as an ion-coupled electron transfer (ET) reaction, where the electronic coupling effect on DLi+ is considered by incorporating the electronic transmission coefficient into the rate constant of the transfer reaction. The new model and DFT calculation results rationalize experimental values of DLi+ for various LiMPO4 (M = Fe, Mn, Co, Ni) materials, which cannot be understood solely by the calculated activation barrier of ion hopping. Interestingly, the electronic coupling between host redox centers is found to play an essential role. Particularly, the sluggish ion mobility in LiFePO4 is due to a very weak electronic coupling. The obtained insights imply that one can improve the rate performance of intercalation materials for metal-ion batteries through modifying the electronic coupling between redox centers of host materials.

Ligand and solvent effects on the kinetics of the electrochemical reduction of Ni(II) complexes: Experiment and quantum chemical modeling

The two-electron reduction of some Ni(II) complexes with α-diimine ligands ([Ni(bpy)3]2+ and [Ni(pybox)2]2+) at a platinum electrode from acetonitrile (AN) and dimethylformamide (DMF) solutions is investigated by cyclic voltammetry (CV). Digisim simulations are employed to determine kinetic parameters. For [Ni(bpy)3]2+ in AN the first electron transfer (ET) step was found to be rate-controlling. The rate constants of the first and second steps (k1 and k2) are practically the same in the DMF solution. In contrast, the second ET step is rate controlling for the [Ni(pybox)2]2+ complex in AN, while the difference between k1 and k2 for this complex reactant in DMF becomes less noticeable. Molecular modeling based on the quantum mechanical theory of electron transfer and on density functional theory (DFT) calculations is performed for the first time to predict the activation barriers of the two-step heterogeneous redox processes and to elucidate the role of the ligands and solvents in the kinetics of these processes. Three-dimensional reaction free energy surfaces are constructed along the solvent and intramolecular coordinates. The electronic transmission coefficients are estimated as well. The results of model calculations are in qualitative agreement with the experimental data.

Enhancement of photoelectron emission efficiency from quantum dot solids, through electrical field biasing of interfaces

It is shown through comparison with experimental results that the efficiency of quantum dot (QD) film-based photoemission would be impacted by an inadequate supply of electrons from an electron source. An explanation for the related photocurrent droop, as arising from restricted electron transmission at the substrate-QD interface as well as between the QDs, is proposed. It is suggested that interfacial potential based biasing schemes could considerably enhance electronic coupling for improved transmission and quantum efficiency. Modeling indicates that electric fields of ∼450 MV/m would be necessary for ensuring electron transmission coefficients close to unity.

Standard units for ElectroChromic Shift measurements in plant biology.

The absorbance shift of pigments is proportional to the membrane potential (Δψ) in plants, green algae, and many photosynthetic bacteria. It is currently denoted as ElectroChromic Shift (ECS) at 515-520 nm for plant carotenoids. It is increasingly being used for phenotyping plants for traits related to photosynthesis or chloroplast metabolism because it is a non-invasive technique and also because more instruments are now commercially available from various manufacturers. The ECS technique is currently used to monitor the post-illumination decay of the proton-motive force (pmf), but it has a more general use for quantitative studies on photosynthetic energy transduction. Here we briefly summarize the basic knowledge on ECS, emphasize the full potential of this technique, and propose a quantitative analysis of the photosynthetic performance with the definition of a transmission coefficient for electrons along the photosynthetic chain.

Effect of Nitrogen on Negative Differential Conductance in Polythiophene Molecular Bridge

Polythiophene is a highly conductive molecule which possesses thermal and chemical stability showing great performance in electrical devices. Polythiophene also shows an uncommon highly demanding electrical property named negative differential resistance which is a decrease of electron current with increase of applied voltage. To address this issue, in this work we study theoretically electron transport properties of a polythiophene molecular bridge sandwiched between two metal leads in the presence of Nitrogen atom as a substitute for one or two of the Carbon atoms in the molecule. The results based on Green’s function formalism show that the presence of Nitrogen reduces the electron transmission coefficient. On the other hand, Nitrogen can lead to amplification of negative differential resistance. Strength of the resistance is affected by the positions and number of Nitrogen atoms in the system. Therefore, choosing right positions for locating impurities is very important. We found that by substituting a Carbon atom with Nitrogen in some positions the system shows notable negative differential resistance. Besides, when two Carbon atoms are replaced by Nitrogen atoms there are some special locations that not only the system shows negative deferential resistance but also it works as an electronic molecular switch which is highly demanding in electronic industry.

Copper Deposition from Chloride-Containing Aqueous Solutions: Catalysis and the Role of the Water Structure

The formation of complexes and the effect of a water network close to the surface on the copper deposition are investigated by means of molecular dynamics simulations. Surprisingly, the presence of chloride has a little effect on the potential of mean force for the approach of a copper ion to an electrode. In addition, the electronic transmission coefficients for Cu2+/Cu+ and [CuCl2]/[CuCl2]− redox couples are calculated in the framework of the modern theory of charge transfer in condensed media. Our results show that the metal influence on the electron transfer (ET) kinetics at the copper deposition results from two important quantities: the work terms and the electronic transmission coefficient. The ET first step proceeds in a near-adiabatic regime for both reactants. The catalytic effect of Cl– is confirmed; the ratio of the calculated rate constants for [CuCl2]/[CuCl2]− and Cu2+/Cu+ was found to be more than two orders of magnitude.

Magnetic Field and Hydrostatic Pressure Effects on Electron Transport in Heterostructure Based on InAs/GaAs Triple Barriers with Dresselhaus Interaction

This paper theoretically examines the spin-dependent transport of electrons through InAs/GaAs symmetric triple barriers by solving the spin-dependent Schrodinger equation. The Transfer Matrix Method (TMM) was used to investigate the impact of the hydrostatic pressure, temperature, and magnetic field on the transmission coefficient and spin polarization of electrons while taking into account the Rashba and Dresselhaus spin orbit interactions. The results indicate that when both the hydrostatic pressure and temperature increase, the two resonant states of spin-up and down electrons move toward lower energies (blue shift). In addition, when the magnitude of the applied magnetic field increases, the resonant states of spin-up electrons shift toward lower energies, whereas the spin-down ones shift toward higher energies, which leads to perfect spin separation. This important spin-separation behavior could be very useful in the design of spin filters, which are strongly required in spintronics applications.

Spectral analysis, chiral disorder and topological edge states manifestation in open non-Hermitian Su-Schrieffer-Heeger chains

We investigate topological and disorder effects in non-Hermitian systems with chiral symmetry. The system under consideration consists in a finite Su-Schrieffer-Heeger chain to which two semi-infinite leads are attached. The system lacks the parity-time and time-reversal symmetries and is appropriate for the study of quantum transport properties. The complex energy spectrum is analyzed in terms of the chain-lead coupling and chiral disorder strength, and shows substantial differences between chains with even and odd number of sites. The mid-gap edge states acquire a finite lifetime and are both of topological origin or generated by a strong coupling to the leads. The disorder induces coalescence of the topological eigenvalues, associated with exceptional points and vanishing of the eigenfunction rigidity. The electron transmission coefficient is approached in the Landauer formalism, and an analytical expression for the transmission in the range of topological states is obtained. Notably, the chiral disorder in this non-Hermitian system induces unitary conductance enhancement in the topological phase.

Subbarrier and Overbarrier Electron Transfer through Multilayer Semiconductor Structures

The transparency coefficients of a semiconductor structure consisting of alternating asymmetric potential barriers and wells, where the Bastard condition is taken into account, are calculated. It is shown that in the structure, an oscillation of the transmission coefficient of electrons depending on their energy is observed, which is caused by the interference of the de Broglie waves coming to the barrier and reflected from the potential barrier. The electronic states of a multilayer semiconductor structure consisting of alternating potential wells and barriers are analyzed.

Thermoelectric Properties of Metallocene Derivative Single-Molecule Junctions

The investigation of electron and phonon transport via molecular nanoscale junctions is one of the fundamental steps in the development of improved high-performance thermoelectric materials for cooling and converting waste heat into electricity. Here, the electrical and thermoelectric properties of metallocenes containing divalent ions Fe, Ni, and Co (ferrocene, nickelocene, and cobaltocene) were investigated. This was achieved by calculating the electronic and phononic transmission coefficients together with the electrical conductance and Seebeck coefficient. The analysis results suggest that the electrical conductance can be tuned by metal substitution, and the thermal conductance due to the electrons across this family of molecules take the order nickelocene > ferrocene > cobaltocene. In contrast, the contribution of phonons to the thermal conductance of these junctions is very insensitive to the selection of the metal atom. Metal substitution has the potential to change both the sign and the amplitude of thermopower.