Modeling of electrotransport properties of Li-intercalated graphene film

In this work, within the framework of density functional theory combined with the method of nonequilibrium Green’s functions the density of states, transmission spectrum, current-voltage characteristics, and differential conductivity of Li-intercalated graphene (LiC6) have been determined. It is shown that in the energy range of -1.3÷-1.05 eV the quasiparticle transport through the nanostructure is disable. The features of IV- and dI/dV-characteristics of LiC6 in the form of decreasing of resistance in the range of -0.4÷0.4 V were revealed, and in the interval of 0.4÷1.4 V formation of negative differential resistance area, related to scattering of quasiparticles. It is established, that LiC6 nanodevice has 12÷13 ballistic channels and has the maximum amount of conductance 12÷13G0 , where Go is the conductance quantum.

Влияние контактной разности потенциалов на вольт-амперные характеристики в сканирующей туннельной спектроскопии

Using the energy diagrams of asymmetric potential barriers formed at the contact of two metals with different work functions, the influence of contact potential difference on the current-voltage characteristics and differential conductivity spectra measured by scanning tunneling spectroscopy is considered. It is shown that the obtained conclusions are in qualitative agreement with the experimental results for ytterbium nanofilms with the thickness of 16 monolayers (6.08 nm). However, they significantly differ quantitatively. The analysis of such diffrences is performed.

Generation of sequences of strong electric monopulses in nitride films

This paper presents theoretical investigation of the excitation of the sequences of strong nonlinear monopulses of space charge waves from input small envelope pulses with microwave carrier frequencies due to the negative differential conductivity in n-GaN and n-InN films. The stable numerical algorithms have been used for nonlinear 3D simulations. The sequences of the monopulses of the strong electric field of 3 - 10 ps durations each can be excited. The bias electric field should be chosen slightly higher than the threshold values for observing the negative differential conductivity. The doping levels should be moderate 1016 -1017 cm-3in the films of ? 2 mm thicknesses. The input microwave carrier frequencies of the exciting pulses of small amplitudes are up to 30 GHz in n-GaN films, whereas in n-InN films they are lower, up to 20 GHz. The sequences of the electric monopulses of high peak values are excited both in the uniform nitride films and in films with non-uniform conductivity. These nonlinear monopulses in the films differ from the domains of strong electric fields in the bulk semiconductors. In the films with non-uniform doping the nonlinear pulses are excited due to the inhomogeneity of the electric field near the input end of the film and the output nonlinear pulses are rather domains.

Electric Transport Properties of a Model Nanojunction “Graphene–Fullerene C60–Graphene”

In the framework of the density functional theory and method of nonequilibrium Green functions (DFT [Formula: see text] NEGF), the electric transport properties of the model nanojunction “Graphene–Fullerene C[Formula: see text]–Graphene” were studied. The transmission spectra, the density of states, the current–voltage characteristic (CVC) and the differential conductivity of the nanojunction are determined. The appearance of a feature of the DOS nanotransition is revealed. This is due to the fact that the Lowest Unoccupied Molecular Orbital (LUMO) of C[Formula: see text] becomes closer to the Fermi level of metal substrates than its Highest Occupied Molecular Orbital (HOMO). It is shown that Coulomb stairs associated with the Coulomb blockade effect appear on the CVC of the nanotransition. The same changes are observed on the differential conductivity spectrum in the form of eight distinct peak structures arising with period [Formula: see text][Formula: see text]V. The comparison of the electric transport characteristics of single-fullerene nanodevices with various electrode materials (graphene, gold, platinum) are presented. It was found that the voltage period of Coulomb features [Formula: see text] in a nanodevice with graphene electrodes is less than in nanodevices with platinum and gold electrodes. It was revealed that the considered nanotransition has negative differential conductivity. The results obtained can be useful in calculating promising elements of single-electronics.

Mechanism for negative differential conductivity in holographic conductors

We clarify the mechanism for negative differential conductivity in holographic conductors. Negative differential conductivity is a phenomenon in which the electric field decreases with the increase of the current. This phenomenon is widely observed in strongly correlated insulators, and it has been known that some models of AdS/CFT correspondence (holographic conductors) reproduce this behaviour. We study the mechanism for negative differential conductivity in holographic conductors by analyzing the lifetime of the bound states of the charge carriers. We find that when the system exhibits negative differential conductivity, the lifetime of the bound states grows as the electric field increases. This suggests that the negative differential conductivity in this system is realized by the suppression of the ionization of the bound states that supplies the free carriers.