An understandable approach to the temperature dependence of electric properties of polymer-filler composites using elementary quantum mechanics

In today’s society, with a high percentage of elderly people, floor heating to ensure constant temperature and heat jackets in winter play important roles in winter to them to live comfortable lives without compromising health – except tropical zones. Under floor heating maintains a comfortable temperature in a room without polluting the air and heat jackets allow for light clothing at comfortable temperatures. The two facilities are attributed to Joule heat generated by tunnel currents between adjacent short carbon fillers in flexible polymer matrixes under low voltage. The current between adjacent conductive fillers is due to electron transfer associated with elementary quantum mechanics. Most of undergraduate students investigating polymer physics will have learned, about electron transfer in relation to the temperature dependence of the conductivity of conductive filler-insulator polymer composites as well as the phenomenon of Joule heat at high school. Despite their industrial importance, most students show little interest for investigating electric properties, since most of polymers are insulation materials. Polymer scientists have carried out qualitative analyses for tunneling current using well-known simplified equations derived from complicated mathematical process formulated by solid-state physicists. Hence this paper is focused on a teaching approach for temperature dependence on electric properties of the polymer-filler composites relating to tunnel current in terms of elementary quantum mechanics. The approach also attempts to bridge education and research by including reference to the application limit of the well-known theories to such complicated composite systems that fillers are dispersed uniformly in the polymer matrix.

Anisotropy and Current Control of Magnetization in SrRuO3/SrTiO3 Heterostructures for Spin-Memristors

Spintronics-based nonvolatile components in neuromorphic circuits offer the possibility of realizing novel functionalities at low power. Current-controlled electrical switching of magnetization is actively researched in this context. Complex oxide heterostructures with perpendicular magnetic anisotropy (PMA), consisting of SrRuO3 (SRO) grown on SrTiO3 (STO) are strong material contenders. Utilizing the crystal orientation, magnetic anisotropy in such simple heterostructures can be tuned to either exhibit a perfect or slightly tilted PMA. Here, we investigate current induced magnetization modulation in such tailored ferromagnetic layers with a material with strong spin-orbit coupling (Pt), exploiting the spin Hall effect. We find significant differences in the magnetic anisotropy between the SRO/STO heterostructures, as manifested in the first and second harmonic magnetoresistance measurements. Current-induced magnetization switching can be realized with spin-orbit torques, but for systems with perfect PMA this switching is probabilistic as a result of the high symmetry. Slight tilting of the PMA can break this symmetry and allow the realization of deterministic switching. Control over the magnetic anisotropy of our heterostructures therefore provides control over the manner of switching. Based on our findings, we propose a three-terminal spintronic memristor, with a magnetic tunnel junction design, that shows several resistive states controlled by electric charge. Non-volatile states can be written through SOT by applying an in-plane current, and read out as a tunnel current by applying a small out-of-plane current. Depending on the anisotropy of the SRO layer, the writing mechanism is either deterministic or probabilistic allowing for different functionalities to emerge. We envisage that the probabilistic MTJs could be used as synapses while the deterministic devices can emulate neurons.

The Nature of CVC Nonlinearity in Low-Voltage Scanning Tunneling Spectroscopy of Semiconductors

A new model of field emission in a scanning tunnelling microscope was developed. The model describes the tunnelling current from a surface of semiconductor (semimetal) and allows estimating the preexponential factor in the expression for the tunneling probability. It is shown that this factor is directly related to the degree of localization of the electron density and determines the shape of the local tunnel current-voltage characteristics (LTCVCs) at low voltages. The model allows separating the contributions of surface electronic states of different symmetry (dimension) of the tunnelling current. The practical application of the model is demonstrated by the example of mathematical processing of the LTCVCs of HOPG surface containing different structural defects.

Распределение кластеров, сформированных sp-=SUP=-2-=/SUP=-- и sp-=SUP=-3-=/SUP=--связями, в углеродной алмазоподобной тонкой пленке

Diamond-like thin films obtained by condensation on carbon metal substrates from a vapor-gas phase are presented. Graphite targets were evaporated by defocused laser radiation. Using the hardware-software complex of a scanning probe microscope in the tunnel current mode, the distribution of regions with sp2 and sp3 bonds in a diamond-like film is analyzed. It is shown that the structure of a diamond-like film consists of large diamond non-conducting fragments with sp3 bonds, along the boundaries of which current regions with sp2 bonds are localized.

Optimal Design of Large Signal and Noise Performance of GaN/SiC Hetero-Structural IMPATT Diodes Based on QCDD Model

Successes of GaN and SiC electronics in high frequency, large power realm indicate that, the GaN/SiC hetero-structures can be used to design the impact avalanche transit time (IMPATT) diodes operating at Terahertz range, of which holds advantages over homo-structural counterparts in lower noise and reduced tunnel current. Here, the (n)GaN/(p)SiC and (p)GaN/(n)SiC double drift region (DDR) IMPATT diodes operating at 0.85 THz are proposed based on the quantum corrected drift-diffusion (QCDD) model, the performance parameters of static state, large signal and noise properties of the studied devices such as peak electric field intensity, breakdown voltage, optimal negative conductance, output power, conversion efficiency, admittance-frequency relation, quality factor, noise electric field, mean-square noise voltage per band-width and noise measure were numerically calculated and analyzed, which can guide to optimize the GaN/SiC IMPATT diodes.

Non-Equilibrium Green’s Function Modeling of the Transport Characteristics of Magnetic Tunnel Junctions Containing Anderson Impurities

A nonequilibrium Green’s function (NEGF) formulation to study the transport characteristics of magnetic tunnel junctions (MTJs) that contains impurities at the barrier region and many-body interaction at the electrode region is presented. The formulation makes use of the already developed NEGF method for MTJs without any impurities and the impurity Green’s function is obtained using Haldane’s approach that explicitly takes into account the on-site Coulomb interaction ([Formula: see text]) of the impurity. The formulation is used to obtain the spin-dependent tunnel current of model MTJs as a function of the applied bias for different values of [Formula: see text] corresponding to both the parallel and antiparallel configuration of the end electrodes of the MTJ. The tunnel currents are used to obtain the tunnel magnetoresistance (TMR) of the MTJ and we observed from our study that the TMR is strongly influenced by the impurities. The TMR is found to be reduced compared to that of the MTJ without impurities and the bias dependence of the TMR is found to be strongly influenced by [Formula: see text]. Our studies revealed that the MTJ can exhibit almost completely spin polarized current at certain values of [Formula: see text].

Разработка и исследование туннельных p-i-n-диодов GaAs/AlGaAs для многопереходных преобразователей мощного лазерного излучения

Fabrication of connecting tunnel diodes with high peak tunnel current density exceeding the short-circuit current density of photoactive p−n junctions is an important task in development of multi-junction III−V photovoltaic converters of high-power optical radiation. Based on the results of a numerical simulation of tunnel diode current−voltage characteristics, a method is suggested for raising the peak tunnel current density by connecting a thin undoped i-type layer with thickness of several nanometers between the degenerate layers of a tunnel diode. The method of molecular-beam epitaxy was used to grow p−i−n GaAs/Al0.2Ga0.8As structures of connecting tunnel diodes with peak tunnel current density of up to 200A/cm2 .

In Situ Raman Spectra of a Conical Conductive Shell as an Electro Galvanic Spin Orbit Transformer (SPOT)

Experimental results are interpreted, which were obtained by tip enhanced Raman Spectroscopy (TERS) in a specific SNOM (Scanning Near-Field Optical Microscope) STM (Scanning Tunneling Microscope) configuration with a tunnel gap. The interpretation is performed in terms of a classical physical model of a photon as a vacuum phonon polariton. The metal tip is considered as a conductive infinitely thin shell of a diamagnetic electron gas. The stationary single electron tunnel current of an electron tunnel passage frequency f tunnel carries not the charge e but is shown to carry an energy hf e and an isotropic orbital angular momentum h/4π which corresponds to an isotropic transversal electron spin density of an angular frequency 2π 2 f e .Raman Spectroscopy, Electron Spin, Photon Spin, relativistic Quantum mechanicsThe electron spin current corresponds to an isotropic azimuthal inertial torque which acts on the photon by an increase of its energy and torque. Neglecting the influence of thermal and radiative losses of the conductive shell, the interpretation reproduces the spectroscopic results within the uncertainty of the experimental results. The photoelectric Raman spectrum of the tunnel gap can be regarded as a complex admittance spectrum which depends in a nonlinear way on the tunnel voltage, the tunnel current and the wavelength of the scattered light. The conical tunnel gap configuration can be considered as a bipolar Electro-Galvanic Spin -Orbit Transformer (SPOT) and from a thermodynamic viewpoint as a Quantum Energy Converter