Showing papers on "Diffusion current published in 2011"
TL;DR: The mechanism of a newly observed photovoltaic effect which occurs in ferroelectrics with periodic domain structures, found in BiFeO(3) films, is elucidated and should occur in any system with a similar periodic potential.
Abstract: We elucidate the mechanism of a newly observed photovoltaic effect which occurs in ferroelectrics with periodic domain structures. Under sufficiently strong illumination, domain walls function as nanoscale generators of the photovoltaic current. The steps in the electrostatic potential function to accumulate electrons and holes on opposite sides of the walls while locally reducing the concentration of the oppositely charged carriers. As a result, the recombination rate adjacent to the walls is reduced, leading to a net diffusion current. In open circuit, photovoltages for periodically ordered domain walls are additive and voltages much larger than the band gap can be generated. The internal quantum efficiency for individual domain walls can be surprisingly high, approaching 10% for above band-gap photons. Although we have found the effect in BiFeO(3) films, it should occur in any system with a similar periodic potential.
343 citations
TL;DR: By evaluating dark lock-in thermography images taken at one reverse and three forward biases, images of all two-diode-parameters J01, J02, n (ideality factor of J02), and Gp (the parallel Ohmic conductivity) of the dark current-voltage characteristic are obtained as discussed by the authors.
96 citations
TL;DR: The diffusion coefficient parallel to the field is strongly affected by the field as well and also approaches a 1/B scaling, in striking contrast to earlier predictions.
Abstract: A first-principles study of diffusion in a strongly coupled one-component plasma in a magnetic field $B$ is presented. As in a weakly coupled plasma, the diffusion coefficient perpendicular to the field exhibits a Bohm-like $1/B$ behavior in the strong-field limit but its overall scaling is substantially different. The diffusion coefficient parallel to the field is strongly affected by the field as well and also approaches a $1/B$ scaling, in striking contrast to earlier predictions.
84 citations
TL;DR: The electrical response of an electrolytic cell in which the diffusion of mobile ions in the bulk is governed by a fractional diffusion equation of distributed order is analyzed.
Abstract: The electrical response of an electrolytic cell in which the diffusion of mobile ions in the bulk is governed by a fractional diffusion equation of distributed order is analyzed. The boundary conditions at the electrodes limiting the sample are described by an integro-differential equation governing the kinetic at the interface. The analysis is carried out by supposing that the positive and negative ions have the same mobility and that the electric potential profile across the sample satisfies the Poisson's equation. The results cover a rich variety of scenarios, including the ones connected to anomalous diffusion.
63 citations
19 Jun 2011
TL;DR: By evaluating dark lock-in thermography images taken at one reverse and three forward biases, images of all two-diode-parameters J 01, J 02, n 2 (ideality factor of J 02 ), and G p (the parallel ohmic conductivity) are obtained.
Abstract: By evaluating dark lock-in thermography images taken at one reverse and three forward biases, images of all two-diode-parameters J 01 , J 02 , n 2 (ideality factor of J 02 ), and G p (the parallel ohmic conductivity) are obtained. A local series resistance is explicitly considered and may be provided as a series resistance image, e.g. resulting from luminescence imaging. The results allow a separate investigation of factors influencing the depletion region recombination current and the bulk lifetime-governed diffusion current.
40 citations
TL;DR: In this paper, the effect of suspended CuO nanoparticles on the mass transfer to a rotating disc electrode was investi-gated experimentally, using the electrochemical limiting diffusion current technique.
39 citations
TL;DR: In this article, the authors studied how the Einstein relation between spontaneous fluctuations and the response to an external perturbation holds in the absence of currents, for the comb model and the elastic single file, which are examples of systems with subdiffusive transport properties.
Abstract: We study how the Einstein relation between spontaneous fluctuations and the response to an external perturbation holds in the absence of currents, for the comb model and the elastic single-file, which are examples of systems with subdiffusive transport properties. The relevance of non-equilibrium conditions is investigated: when a stationary current (in the form of a drift or an energy flux) is present, the Einstein relation breaks down, as is known to happen in systems with standard diffusion. In the case of the comb model, a general relation, which has appeared in the recent literature, between the response function and an unperturbed suitable correlation function, allows us to explain the observed results. This suggests that a relevant ingredient in breaking the Einstein formula, for stationary regimes, is not the anomalous diffusion but the presence of currents driving the system out of equilibrium.
28 citations
TL;DR: This procedure allows the construction of general expressions for the electrochemical impedance satisfying the Kramers-Kronig relations when the diffusion of ions in the cell is characterized by the usual, as well as by anomalous, behavior.
Abstract: The contribution of ions to the electrical impedance of an electrolytic cell limited by perfect blocking electrodes is determined by considering the role of the anomalous diffusion process and memory effects. Analytical solutions for fractional diffusion equations together with Poisson’s equation relating the effective electric field to the net charge density are found. This procedure allows the construction of general expressions for the electrochemical impedance satisfying the Kramers‐Kronig relations when the diffusion of ions in the cell is characterized by the usual, as well as by anomalous, behavior. (Some figures may appear in colour only in the online journal)
23 citations
TL;DR: In this article, a three-current model is used to predict the spin Seebeck effect on large-scale diffusion currents on large scales, which is known as the Soret effect or thermophoresis.
Abstract: Using a three-current model (i.e. heat, spin-up and spin-down electrons) the thermodynamics of irreversible processes predicts that a temperature gradient gives rise to a spin current on large scales, in particular under the conditions used to measure the spin Seebeck effect. Diffusive currents on large scales are common in thermochemistry. The proportionality between the diffusion current and the gradient of the chemical potential is known as the Soret effect or thermophoresis. (C) 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
22 citations
TL;DR: In this paper, an improved analytical model of InGaAs-based focal plane arrays is proposed to predict the ultimate dark current limits for tight-pitch arrays, which can explain how tight pitch arrays suppress diffusion current and why bulk generation-recombination is not a limiting factor.
Abstract: InGaAs-based focal plane arrays are an unrivaled uncooled SWIR technology. Prior analytical models of InGaAs have
been inaccurate at predicting the ultimate dark current limits for tight-pitch arrays. By going back to first-principles, we
have developed an improved analytic model. This model clarifies how tight pitch arrays suppress diffusion current and
why bulk generation-recombination is not a limiting factor in today's devices. We can thus explain our experimental
arrays with dark currents of 0.5nA/cm2 at 20C and <0.1nA/cm2 at 7C as well why we believe another order of
magnitude decrease in dark current is theoretically possible.
17 citations
TL;DR: In this article, an analysis of the transport of electric current in a jet of an electrically conducting liquid discharging from a metallic tube into a gas or a vacuum, and subject to an electric field due to a high voltage applied between the tube and a far electrode is presented.
Abstract: This paper presents an analysis of the transport of electric current in a jet of an electrically conducting liquid discharging from a metallic tube into a gas or a vacuum, and subject to an electric field due to a high voltage applied between the tube and a far electrode. The flow, the surface charge and the electric field are computed in the current transfer region of the jet, where conduction current in the liquid becomes surface current due to the convection of electric charge accumulated at its surface. The electric current computed as a function of the flow rate of the liquid injected through the tube increases first as the square root of this flow rate, levels to a nearly constant value when the flow rate is increased and finally sets to a linear increase when the flow rate is further increased. The current increases linearly with the applied voltage at small and moderate values of this variable, and faster than linearly at high voltages. The characteristic length and structure of the current transfer region are determined. Order-of-magnitude estimates for jets which are only weakly stretched by the electric stresses are worked out that qualitatively account for some of the numerical results.
TL;DR: In this paper, a transition between two different dendritic growth regimes in the electrodeposition of a metal from a binary electrolyte was studied using two different optical techniques: laser interferometry and optical absorption due to Cu 2+ ion.
TL;DR: In this article, the effect of spin-dependent electric field on magnetization dynamics was examined and it was shown that the spin current is a nonlocal function of the spin motive force and can be expressed in terms of nonlocal Gilbert damping tensor.
Abstract: Spin motive force is a spin-dependent force on conduction electrons induced by magnetization dynamics. To examine its effects on magnetization dynamics, it is indispensable to take into account spin accumulation, spin diffusion, and spin-flip scattering since the spin motive force is, in general, nonuniform. We examine the effects of all these on the way the spin motive force generates the charge and spin currents in conventional situations, where the conduction electron spin relaxation dynamics is much faster than the magnetization dynamics. When the spin-dependent electric field is spatially localized, which is common in experimental situations, we find that the conservative part of the spin motive force is unable to generate the charge current due to the cancellation effect by the diffusion current. We also find that the spin current is a nonlocal function of the spin motive force and can be effectively expressed in terms of nonlocal Gilbert damping tensor. It turns out that any spin-independent potential such as Coulomb potential does not affect our principal results. At the last part of this paper, we apply our theory to current-induced domain wall motion.
TL;DR: In this article, it was shown that very small wave electric field amplitude, of the order of 10 −7 V/m, within one wave period can produce the drift of protons in both directions, perpendicular to the ecliptic plane and also along the background magnetic field, to distances measured in millions of kilometers.
Abstract: Transport and diffusion of plasma particles perpendicular and parallel to the magnetic field is discussed in the framework of the transverse drift wave theory. The starting model includes the density and magnetic field gradients perpendicular to the magnetic field vector. In such an inhomogeneous environment the transverse drift wave naturally develops. The transverse drift wave is a low frequency mode, with the frequency far below the ion gyro-frequency, it is driven by these gradients and it propagates perpendicular to them. The mode is also purely perpendicular to the magnetic field and it is electromagnetically transverse, which implies that when its wave vector is perpendicular to the magnetic field vector, the perturbed electric field is along the equilibrium magnetic field, while in the same time the perturbed magnetic field is in the direction of the background gradients. In application to the solar wind, it is shown that very small wave electric field amplitude, of the order of 10 −7 V/m, within one wave period can produce the drift of protons in both directions, perpendicular to the ecliptic plane and also along the background magnetic field, to distances measured in millions of kilometers. The electric field along the magnetic field vector implies particle acceleration in the same direction. When a critical threshold velocity of the particle is achieved, the particle motion becomes stochastic. This is a completely new nonlinear stochastic mechanism which follows from the very specific geometry of the transverse drift mode. Particle drift perpendicular to the magnetic field vector means a diffusion of particles, with the effective diffusion coefficient for ions that is at least 11 orders of magnitude larger than the classic diffusion coefficient. The features of this diffusion are: within certain time interval, initially faster particles will diffuse to larger distances, and the same holds for protons in comparison to heavier ions. For electrons the effective diffusion coefficient can easily match the one obtained from observations, i.e., to become of the order of 10 17 m 2 /s. It is also expected that the wave-induced stochastic motion will considerably increase the effective collision frequency in such an environment which is, with respect to its mean parameters, practically collision-lees. Hence, the solar wind regions affected by such a stochastic acceleration may show various unexpected features that are typical for collisional plasmas.
TL;DR: In this paper, a general description of the interplay between the Kirkendall shift (as a special way of relaxation) and diffusion induced driving forces in diffusion intermixing of binary systems is given.
Abstract: General description of the interplay between the Kirkendall shift (as a special way of relaxation) and diffusion induced driving forces in diffusion intermixing of binary systems is given. It is shown that, if the Kirkendall shift is negligible, a steady state Nernts-Planck regime is established with diffusion coefficient close to the slower diffusivity, independently of the type of the diffusion induced field and also independently whether this is a single field or a combination of different fields (e.g. stress field and extra chemical potential of non-equilibrium vacancies). Deviations from parabolic kinetics are expected only before or after this steady state stage. Using the results of our previous paper, on development and relaxation of diffusion induced stresses, it is illustrated that the setting of time of the Nernst-Planck regime is very short: intermixing on the scale of few tenths of nanometer is enough to reach it. It is also illustrated that this stage is realized even in the case of asymmetric interdiffusion (in one side of the diffusion zone the diffusion is orders of magnitude higher than in the other), when the stress distribution has a more complex form (having a sharp peak at the interface). Surprisingly the steady state is longer than it would be expected from the relaxation time of Newtonian flow: This is so because the composition profile is not static but changes fast in the timescale of the stress relaxation, and thus the stress re-develops continuously.
TL;DR: A traditional model used to describe the current-voltage dependence of low mobility materials sandwiched between planar electrodes is reformulated by using the quasi-electrochemical potential as the fundamental variable instead of the local electric field or the local charge carrier density to allow the material density-of-states to enter explicitly in the equations.
Abstract: We have reformulated a traditional model used to describe the current–voltage dependence of low mobility materials sandwiched between planar electrodes by using the quasi-electrochemical potential as the fundamental variable instead of the local electric field or the local charge carrier density. This allows the material density-of-states to enter explicitly in the equations and dispenses with the need to assume a particular type of contact. The diffusion current is included and as a consequence the current–voltage dependence obtained covers, with increasing bias, the diffusion limited current, the space-charge limited current, and the injection limited current regimes. The generalized Einstein relation and the field and density dependent mobility are naturally incorporated into the formalism; these two points being of particular relevance for disordered organic semiconductors. The reformulated model can be applied to any material where the carrier density and the mobility may be written as a function of ...
Posted Content•
TL;DR: In this paper, a phenomenological model of conductivity was developed using the generalized continuity equations, and a limiting conductivity is obtained that amounts to 1.09 × 10 9 Ω −1 m −1.
Abstract: Application of the generalized continuity equation reveals that the drift current in conductors is equivalent to a negative diffusion current. A phenomenological model of conductivity is developed using the generalized continuity equations. Consequently, a limiting conductivity is obtained that amounts to 1.09 × 10 9 Ω −1 m −1 . A magnetomotive force (current) is hypothesized to exist, which is exhibited when a voltage changes with time. Magnetic charges and currents are found to be related to displacement current. PACS: 14.80.Hv 03.50.De 11.30.Er
TL;DR: In this paper, a mathematical modeling of the mobility of Ag + ion in AgI is presented, where the depolarization potential is recorded at various isothermal conditions in the temper-ature range 300-535 K.
Abstract: A mathematical modeling of mobility of Ag + ion in AgI is presented. In the model, regime is space charge polarized initially by applying a fixed d.c. field of ∼0.5 V across the sample, sandwiched between two electronically conducting graphite electrodes. The depolarization potential is recorded at various isothermal conditions in the temper- ature range 300-535 K. By considering open-circuit condition (where the sum of all current densities, i.e., drift current density, trapped current density, and displacement current density, is vanished), ionic drift- and trap-modulated mobilities are modeled. Result obtained through this model is compared with the ionic mobility, measured by conven- tional transient ionic current technique in the same temperature range.
TL;DR: The relationship between the space charge and the current density is consistent with the voltage-current characteristics, and can reflect the nonlinear characteristics of ZnO varistors as discussed by the authors, which can reveal the conduction mechanism.
Abstract: In order to reveal the conduction mechanism of ZnO varistor, the pulsed electroacoustic (PEA) measurement is employed to investigate the space charge distribution characteristics of ZnO varistors under different current densities in this paper. Experimental results show that the relationship between the space charge and the current density is consistent with the voltage-current characteristics, and can reflect the nonlinear characteristics of ZnO varistor. The space charge increases linearly with the increase of the electric field strength and the current density in the small current region, this reflects the decrease of the surface states of the grain boundary and changes of the Schottky barrier. There exists a transition region between the small current and middle current regions, where the current is composed of the current by the emission of thermally activated electrons and the tunneling current. In the middle current region, the space charge will decrease as the current increases, and will disappear with the depletion layer decreasing to zero.
01 Jan 2011
TL;DR: The first task of an optical receiver is to convert the signal from the optical domain to the electrical domain, which is performed by the photodiode which is discussed thoroughly in this paper.
Abstract: The first task of an optical receiver is to convert the signal from the optical domain to the electrical domain. This is performed by the photodiode which is discussed thoroughly in this chapter.
TL;DR: In this paper, the relationship between the radial electric field and radial current in tokamak plasmas, especially when heated by neutral beam injection, was analyzed in a rigorous manner.
Abstract: The fluid equation is analytically derived in a rigorous manner, stipulating the relationship between the radial electric field and radial current in tokamak plasmas, especially when heated by neutral beam injection. On a very short time scale compared to the decay in poloidal rotation, the polarization current compensates for the non-ambipolar fast-ion radial current, producing a concomitant time change in the radial electric field. This polarization current predominates among the constituents of the radial current that produces the j × B torque. For times comparable to or longer than the decay time, the polarization current is no longer sufficient to compensate for the fast-ion radial current. In a steady state where the radial electric field is constant over time, the polarization current vanishes and the orthogonal conduction current becomes a sole component of the radial current that continues to flow as long as the charge separation occurs due to the neutral beam injection. Analytical work demonstra...
Patent•
16 Feb 2011
TL;DR: In this article, a forward biased voltage is applied to generate a diffusion current in a junction 35 between a p layer 14 and an n layer 13, and the surface shape and/or dopant distribution of either layer is changed based on Joule heat produced by a generated diffusion current, the process of which is repeated.
Abstract: PROBLEM TO BE SOLVED: To provide a photodetector fabrication method which makes it easy to fabricate elements provided with sensitivity to a specific wavelength without having to select a material.SOLUTION: A forward biased voltage is applied to generate a diffusion current in a junction 35 between a p layer 14 and an n layer 13, and the surface shape and/or dopant distribution of either layer is changed based on Joule heat produced by a generated diffusion current, the process of which is repeated. In places where near-field light is generated, the diffusion current is reduced by stimulated emission it in plural steps by a diabatic process based on inverted population, thereby reducing the Joule heat, in which way the surface shape and/or dopant distribution is fixed.
Patent•
10 Aug 2011
TL;DR: In this paper, a deep energy level impurity ionizing collision transistor belonging to the fields of field effect transistor logic devices and circuits in a CMOS (Complementary Metal Oxide Semiconductor) ultra large scale integrated circuit (ULSI) is presented.
Abstract: The invention provides a deep energy level impurity ionizing collision transistor belonging to the fields of field effect transistor logic devices and circuits in a CMOS (Complementary Metal Oxide Semiconductor) ultra large scale integrated circuit (ULSI). The transistor comprises the same N-type or P-type doped source electrode and drain electrode, a control gate and a high-resistance drift region, wherein the drift region comprises deep energy level impurities which can ionize carriers under a high field; leakage current of the device can be reduced by the high-resistance drift region in an off state; and a large amount of carriers can be instantly provided when the device is in an on state, so that the on of the device is promoted. Compared with the conventional low-power-consumption device TFET (Tunneling Field Effect Transistor), since drift diffusion current is adopted, larger on current and steeper sub-threshold frequency can be achieved. Compared with the conventional low-power-consumption device IMOS (Ion Implanted Metal Oxide Semiconductor), since a critical electric field of deep energy level impurity ionization is far lower than an avalanche critical electric field, the reliability of the device can be enhanced while working points of the device are greatly reduced.
TL;DR: In this article, the ideality factor of amorphous silicon (a-Si:H) solar cells is analyzed as a function of both the thickness of the intrinsic layer and the applied voltage to the cells.
Abstract: This paper analyzes the ideality factor of amorphous silicon (a-Si:H) solar cells as a function of both the thickness of the intrinsic layer and the applied voltage to the cells. The ideality factor in this work is extracted from the current/voltage characteristic that is calculated by solving the continuity and transport equations and taking into account the contributions of diffusion and drift currents for minority and majority carriers and, especially, the nonequality of mobilities and lifetimes of electrons and holes in a-Si:H solar cells.
01 Sep 2011
TL;DR: In this article, an improved PEA (pulsed electro-acoustic) measurement system was developed to measure the space charge distribution and external current in low density polyethylene (LDPE).
Abstract: Space charge distribution and external current in low density polyethylene (LDPE) have been measured simultaneously using an improved PEA (pulsed electro-acoustic) measurement system. They are usually measured using different devices independently. However, to investigate the relationship between the space charge behavior and the conduction current, it is necessary to measure them simultaneously in the same sample. Therefore, we have developed an improved PEA system to measure them simultaneously. In this improved system, the space charge distribution and the external current measurements are carried out by switching connection of the lower electrode between electrometer and ground. As the result of simultaneous measurements, it is found that the external current increases during the injection and traveling of positive charge from the anode towards the cathode. To explain the phenomenon, we estimated displacement current, conduction current and conductivity distributions in the sample from the results of the measurements. Moreover, we examined the relationship between those distributions and charge behavior in LDPE.
05 Sep 2011
TL;DR: In this paper, a model for a 1D Si-based light-emitting p-i-n diode (LED) is presented, describing DC electrical characteristics and the internal quantum efficiency as a function of the applied bias.
Abstract: A new model for a 1D Si-based light-emitting p-i-n diode (LED) is presented, describing DC electrical characteristics and the internal quantum efficiency (_IQE) as a function of the applied bias, showing good agreement with the simulation results. An optimization scheme, based on the model, shows improved _IQE for engineered heterojunctions by reducing the diffusion current.
TL;DR: In this article, a method for calculating activation energy of silicon p-n junctions from volume generation current is presented. But the method is limited to the case where the volume diffusion current is subtracted from the volume leakage current, and the activation energy is derived from slope of an Arrhenius plot of diffusion current.
Abstract: Diode leakage current consists of diffusion (Id) and generation current (Ig), which is strongly sensitive to the residual defect density. These defects can be studied by activation energy (Ea). Therefore, this paper presents a method for calculating activation energy of silicon p-n junctions from volume generation current. It combines temperature-dependent current–voltage (I –V) and capacitance–voltage (C-V) measurements of diodes. The Ig can be found from the volume leakage current by subtraction of the volume diffusion current, which is calculated while the depletion width is zero. The activation energy (Ea) is derived from slope of an Arrhenius plot of Ig. To derive the correct slope the temperature dependence of the depletion width, which is obtained from the corrected volume capacitance has been applied. The Ea profile below junction has been shown. The lower Ea value has been found near the junction, which may relate to the junction implantation.
TL;DR: In this article, the authors investigated the vertical transport in p-i-n diodes containing InGaP/GaAs multi-quantum-wells (MQW) using current-voltage measurements under forward bias at different temperatures.
Abstract: Vertical transport in p-i-n diodes containing InGaP/GaAs multi-quantum-wells (MQW) is investigated using current-voltage measurements under forward bias at different temperatures. At low injection, the experimental data are analyzed through a two diode model, by taking into account the non-complete depletion of the MQW region caused by unintentional p-type doping. The diffusion current results to be dominant at high temperatures, whereas the current due to non-radiative recombination through defects in the space charge region becomes more and more relevant as the temperature is reduced. At temperatures above T = 150 K and at high forward voltages, when the current is limited by the series resistance, the thermionic emission of holes over the InGaP barriers controls the transport through the whole MQW region. At lower temperatures resonant tunneling of holes takes place and a simple picture of the hole quantum levels permits to interpret the main details of the I(V) curves at T = 41 K, by supporting the hy...
14 Sep 2011
TL;DR: In this article, the authors demonstrate increased light emission in Si p-i-n light emitting diodes (LEDs) by changing the geometry of the device, reducing the injector size, decreasing the diffusion current as shown by IV measurements and simulations, as a result, for a particular on-current the pn product and hence light increases inside the active region for the new devices.
Abstract: This paper demonstrates increased light emission in Si p-i-n light emitting diodes (LEDs) by changing the geometry of the device. The theory behind this, the device fabrication, electrical and optical characteristics are also presented. Reducing the injector size, decreases the diffusion current as shown by IV measurements and simulations. As a result, for a particular on- current the pn-product and hence light increases inside the active region for the new devices. The electroluminescence (EL) intensity measurements show an enhanced light emission by more than a factor of four.
TL;DR: In this article, the spin-drift-diffusion theory and Ohm's law were used to obtain the charge current polarization, which took into account the special carriers of organic semiconductors.
Abstract: Spin-polarized injection and transport into ferromagnetic/organic semiconductor structure are studied theoretically in the presence of the external electric field and magnetic induction. Based on the spin-drift–diffusion theory and Ohm's law, we obtain the charge current polarization, which takes into account the special carriers of organic semiconductors. From the calculation, it is found that the current spin polarization is enhanced by several orders of magnitude by tuning the magnetic induction and electric fields. To get an apparent current spin polarization, the effects of spin-depended interfacial resistances and the special carriers in the organic semiconductor, which are polarons and bipolarons, are also discussed.