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31.
《Physics letters. A》2020,384(19):126399
In this work we investigate a generalized tunneling barrier for planar emitters at zero-temperature. We present the evidence of the emergence of a non-Fowler-Nordheim-type general behavior for the field emission current density in the case that the Fermi energy (μ) is comparable with or smaller that the decay width (). Therefore, for some non-metals or materials that have very small Fermi energy the standard Fowler-Nordheim-type theory may require a correction. In the opposite regime, i.e., for μ much larger that , we confirm that the conventional theory is suitable for metals. 相似文献
32.
We study the effective manipulation of the Andreev bound states (ABS), zero mode Majorana fermion and Josephson current (JC) in a superconductor–normal–superconductor junction on the surface of a topological insulator in unexplored regime of parameters. It is found that the energy of the ABS changes dramatically with the phase difference between both superconductors (SCs) in a certain range of the incident angle of quasiparticles. It is shown that the velocity of Majorana fermion and the JC can be effectively tuned in a wide range of the chemical potential in the normal region (μN) and the separation width (L ) of the two SCs. In addition, we expose that the critical JC and its product with the normal resistance are, respectively, a quarter and the same to those in a graphene-based Josephson junction. The dependence of the critical JC on the chemical potential in the superconducting region is not monotonous: it increases (decreases) for small (large) μN. 相似文献
33.
In this paper, n-Zinc oxide/p-copper oxide heterojunctions were fabricated by RF-sputtering on indium tin oxide-covered glass substrates. The structural and optical properties of the copper oxide and zinc oxide films were analyzed by X-ray diffraction, Fourier transform infrared, scanning electronic microscopy and ultraviolet-visible spectroscopy. The electrical junction properties were investigated by current–voltage (I–V) characteristics. Additionally, both capacitance (C) and conductance (G) versus frequency (f) measurements were realized at room temperature. The junctions showed a rectifying behavior, and C and G varied with both voltage and frequency. 相似文献
34.
The main mechanisms of leakage currents in thin lead zirconate titanate (PZT) ferroelectric films prepared by the sol–gel method are discussed. Four specific regions are determined in I–V dependencies. At very weak fields (10–20 kV/cm), the current falls with the voltage increase as a result of depolarization. In the low fields region (about 70–100 kV/cm), the leakage current decreases with the decrease of voltage ramp speed and its components are the ohmic and displacement currents. In the high fields region (≥130 kV/cm), the leakage current increases with the decrease of step voltage ramp in contrast to the previous case. Possible conductivity mechanisms are the Poole– Frenkel emission and hopping conduction. In the transition region between above-mentioned ones (from 80–90 to ~130 kV/cm), an abrupt unstable increase of current is observed caused by breakdown of reverse bias Schottky barrier. Depolarization currents are studied for sol–gel PZT films prepared at different preparation conditions. 相似文献
35.
We study the problem of spin current pumping in a one-dimensional quantum wire when there exist two orthogonal Rashba spin-orbit couplings (SOCs) in different regions which evolve with time and can be induced by the perpendicular electric fields. On one hand, we demonstrate that the time-evolving Rashba SOC is equivalent to the spin-dependent electric field and the scheme may lead to the pure spin current associated with well suppressed charge current. On the other hand, we adopt the non-equilibrium Green's function method and numerically find that the parameter loop must satisfy certain condition for the successful pumping. We also study the effect of the Fermi energy and the inevitable disorder on the spin current. The implications of these results are discussed. 相似文献
36.
37.
《Journal of computational science》2014,5(2):269-276
Growing interconnection in distribution system creates new problem for protection engineers. Particularly the design of overcurrent relay coordination in such system is an independent area of research. With the availability of new artificial based optimization algorithm relay coordination research gain a new momentum. Well established artificial based optimization algorithm such as genetic and particle swam optimization are successfully applied for such applications. This paper discusses the application of informative differential evolution algorithm with self adaptive re-clustering technique for selection of TDS and PSM for optimal coordination of directional overcurrent relays. Both continuous as well as discrete version of informative differential evolution algorithm are used for optimization of relay setting. Proper combination of backup relays for each primary relay are identified by using LINKNET graph theory approach. Coordination of directional overcurrent is developed for 9 bus and IEEE 30 bus distribution systems. The aim of problem is to minimize the total operating time of primary relays and eliminate the miscoordination among the primary and backup relay pairs. Discrete types of settings for electromechanical types of relay are also discussed in this paper. Moreover, the relay coordination problem is modified for providing optimal coordination time interval between 0.2 and 0.8 s among all primary and backup relays pairs. The results are compared with hybrid of genetic algorithm – nonlinear programming and sequential quadratic programming. Digsilient power factory software is used for verification of result. 相似文献
38.
39.
Hiroshi Ishiwara 《Current Applied Physics》2012,12(3):603-611
Impurity substitution effects in BiFeO3 thin films are reviewed from a viewpoint of FeRAM (ferroelectric random access memory) applications, in which such characteristics as a large remanent polarization, a low coercive voltage, and excellent fatigue endurance are most important. First, it is described that substitution experiments for Bi and Fe atoms in the films have already been conducted using almost all rare earth and transition metal elements. A list of the published paper is given in a form of the periodic table of elements. Then, two typical cases, La substitution for the Bi site and Mn substitution for the Fe site, are reviewed in detail. Particular attention is paid to the role of these impurity atoms by which the ferroelectric and insulating properties of BiFeO3 films are significantly improved. Finally, impurity effects due to substitution or co-substitution of other elements are reviewed. 相似文献
40.
陈怀宁 《浙江大学学报(理学版)》1986,13(3):305-308
本文研究电涡流传感器的探测线圈与电涡流之间的电磁作用力。理论计算与测量结果表明,对于某些应用电涡流传感器的灵敏装置而言,这个力的影响是不能忽略的。 相似文献