Showing papers on "Electric potential published in 1971"

A Consideration of Poole‐Frenkel Effect on Electric Conduction in Insulators

Abstract: The extended Poole‐Frenkel model presented here includes the variation of the barrier height with electric field in directions both opposite and forward to the electric force on an electron The equation for the voltage‐current characteristics based on this model gives not only the usual Poole‐Frenkel equation at extremely high electric fields but also Ohm's law at low fields Several published experimental data are in good agreement with this equation

Electric Field Gradients at 57Fe in ZnFe2O4 and CdFe2O4

Abstract: The nuclear quadrupole coupling constants and isomer shifts of 57Fe in the spinels ZnFe2O4 and CdFe2O4 were measured using the Mossbauer effect. The signs of the quadrupole coupling constants were determined from spectra which were taken in an applied magnetic field. The sign is negative in both spinels. The isomer shifts and Fe–O distances indicate that Fe3+ in ZnFe2O4 is somewhat more covalently bonded than in CdFe2O4. The external field gradients at the Fe3+ positions can be interpreted in terms of the ionic point‐multipole model modified by some charge transfer between oxygen and the cations. The point charge contribution to the field gradient is positive in case of ZnFe2O4 and nearly zero in case of CdFe2O4; the predominant contribution is due to the electric dipole moments of the oxygen ions and is negative. The dipole polarizability of the oxygen ion which gave the best fit is αD = 0.8 A3. The effect of charge transfer on the ionic field gradient is small.

Electrons in Crystals in a Finite-Range Electric Field

Abstract: The problem of an electron in a finite-range constant electric field is treated; energy levels and eigenfunctions are calculated for the "empty crystal" and for a Mathieu-type model crystal. It is shown that the addition of boundary conditions may change the solution drastically. The influence of different boundary conditions on the eigenvalues and eigenfunctions is discussed and it is found that the former are relatively insensitive while the latter are sensitive to a change in boundary conditions. The result for the eigenvalues is shown to be consistent with an extension of the Born-Ledderman theorem to electronic states in finite crystals. The effective-mass approximation is shown to hold for this model even for moderate fields and use is made of it to explain the complex behavior of the wave functions near the bands' edges. All in all, a clear detailed picture, although limited in scope, is presented of properties of electrons in crystals under the influence of external electric fields.

On electronic conduction through evaporated silicon oxide films

Abstract: A new model is proposed to explain the voltage-current characteristics of evaporated silicon oxide films in the whole range of electric field intensity, in which one sort of Poole-Frenkel effect is used and the current conduction is thought of as due to the carrier jumps over the coulomb potential wall from the occupied Poole-Frenkel sites to the empty ones. The voltage-current characteristics are calculated and compared with existing experimental data. We found good agreement between the calculated results of this model and the experimental results.

Low-Energy Electron-Diffraction Intensity Calculations for Beryllium with a Realistic Crystal Potential

Abstract: The band-matching approach is used to calculate low-energy electron-diffraction intensity-voltage curves for the basal cleavage plane of beryllium. An approximation to the exact theory, made possible by the presence of strong inelastic scattering, enables these curves to be calculated very rapidly, for general angles of incidence and with a detailed nonlocal potential. The potential is constructed from first principles, includes thermal and inelastic-scattering effects, and has no adjustable parameters. Over a wide range of incident angles the calculated curves show marked agreement with recent experiments. A test of the sensitivity of the calculations to changes in the scattering potential parameters shows that the absolute intensity, rather than peak position or peak width, should be the best experimental probe of the scattering processes. A new approximation for core-valence exchange is used in the calculation and is described in an appendix.

Electric Field Distriutions in Dielectrics, with Special Emphasis on Near-Surface Regions in Ferroelectrics

Abstract: The characteristics of the electric field distribution due to space-charge currents in dielectric materials with both linear and nonlinear polarization are discussed, and analytic and numerical solutions for zero current are presented. In considering Poisson's equation for a material with a position-dependent polarization, we find it convenient to define a dielectric parameter in terms of the internal-electric-field derivative of the polarization rather than their quotient. In the static situation the largest electric fields exist near the surfaces for all dielectrics. Introducing the nonlinear dielectric parameter into the one-carrier model including diffusion exaggerates the effect. We expect that the strongest indications for such behavior occur in ferroelectrics since their dielectric properties are the most field sensitive. The diffusionless two-carrier recombination-center model is briefly considered. We discuss an example from the literature in terms of our "amplified-space-charge region" model and comment upon implications for device usage.

Engineering Applications of Current and Potential Distributions in Disk Electrode Systems

Abstract: Integral transform methods for analytic solutions to current and potential distribution on disk in infinite plane for four limiting cases

Surface potential of a photoemitting plate

Abstract: Earlier work [Guernsey and Fu, 1970] studied the potential distribution in the neighborhood of a photoemitting plate immersed in plasma. The result indicates that two steady state potential distributions can exist, namely one in which the potential decreases from its plate value to zero monotonically and one in which it decreases from its plate value to a negative minimum and then increases to zero (‘overshoot’ type). In the present work a Maxwellian distribution is assumed for the emitting photoelectrons instead of a Fermi shape distribution. Furthermore the difference of the surface potential for these two types of distributions is investigated in more detail. The result shows that this difference can exist only if 1

Pull‐In Phenomena of Josephson Oscillators

Abstract: Constant voltage steps in dc current‐voltage characteristics occur by assuming pull‐in phenomena. Based on this concept, steps above the gap voltage and frequency dependence of the step amplitudes are found.

Magnetohydrodynamic duct flow in a uniform transverse magnetic field of arbitrary orientation

Abstract: The paper presents an approximate analysis for high Hartmann number of the flow of an electrically conducting, incompressible fluid in a duct of square crosssection, having one pair of opposite walls insulating, and the other pair perfectly conducting and inclined at arbitrary orientation to a uniform transverse magnetic field. The flow is considered to be either pressure-driven with the two perfectly conducting electrodes short-circuited together or electrically driven by a potential difference applied between these electrodes in the absence of axial pressure gradient. The paper describes experiments on the pressure-driven, short circuited case using mercury in copper ducts to investigate the variation of the streamwise pressure gradient and of the potential distribution along one insulating wall with orientation, magnetic field and flow rate.At general orientations the analysis suggests and the experiments confirm the existence of regions of stationary fluid in the corners of the duct, together with viscous shear layers parallel to the magnetic field. For the case in which the electrodes are parallel to the magnetic field the experimental results for the pressure gradient, but not those for the potential distribution, agree reasonably well with Hunt & Stewartson's (1965) asymptotic solution. Both pressure gradient and potential results agree closely with the analysis by Hunt (1965) of the case in which the electrodes are perpendicular to the magnetic field.

High current density electrolytic cell

Abstract: APPARATUS FOR RECOVERING A METAL FROM A SOLUTION IN WHICH THE METAL IS PRESENT IN IONIC FORM, INCLUDING A PAIR OF OPPOSITELY DISPOSED ELECTRODES SEALED TO AND SEPARATED BY AN ELECTRICALLY NON-CONDUCTIVE SPACING ELEMENT WHICH FORMS A DISK-SHAPED CHAMBER THROUGH WHICH THE SOLUTION IS CIRCULATED AND MEANS FOR IMPRESSING AN ELECTRIC POTENTIAL ACROSS THE ELECTRODES TO CAUSE THEMETAL IONS IN THE SOLUTION TO PLATE OUT ON THE ELECTRODE SURFACE OF LOWER POTENTIAL. THE APPARATUS IS PARTICULARLY WELL ADAPTED TO RECOVERING SILVER FROM FIXING SOLUTIONS EMPLOYED IN PHOTOGRAPHIC PROCESSING AND PERMITS SUCH RECOVERY TO BE EFFECTED AT EXCEPTIONALLY HIGH CURRENT DENSITIES.

Calculation of the Force Acting on an Impurity in a Metal Submitted to an Electric Field or a Temperature Gradient

Abstract: Abstract Using the Bosvieux-Friedel polarization model, the charge carrier induced force on an impurity in a normal metal submitted to a temperature gradient or an electric field is calculated, and a connection is made between the two phenomena. The results are interpreted in terms of the specific resistivity and thermoelectric power of the impurity in the matrix. A crude estimation of the force due to phonon scattering on an impurity in a temperature gra dient is given

Electric potential near a spherical body in a conducting half-space

Abstract: An extensive summary of classical potential solutions has been given recently by Van Nostrand and Cook (1966). This note presents a solution for the potential due to a point source of electric current placed on the earth’s surface in the vicinity of a buried spherical body of arbitrary resistivity. The analysis follows the procedure suggested by Van Nostrand and Cook and is similar to that used recently by Merkel (1969, 1971).

Process for producing a color state in a display device

Abstract: This disclosure is directed to articles of manufacture, chiefly display devices, containing minute "naked" droplets or inclusions of cholesteric liquid crystal material in a substantially continuous polymeric matrix, said liquid crystal material changing color or shade of color not only upon application of an electric potential but also upon removal of the field. The image produces has a comparable outline to that of the path of the electric field. Three chromatic states are evident, the normal color (before the electric potential is applied), the color given off when the electric field is applied, and the color observed when the electric field is removed. All three chromatic states are readily discernible from one another. The polymer matrix protects the cholesteric liquid crystal droplets from aging and enhances electric field behavior because the third chromatic state (electric potential removed) has a greater longevity with the matrix-bound material versus unprotected material of identical composition but no polymeric matrix. Other advantages are also discussed.

Altitude variations in the electrical potential resulting from orographic features

Abstract: The two-dimensional differential equation which governs the electrical potential of an atmosphere whose conductivity is given by $$\lambda = \lambda _0 \operatorname{e} ^{\beta z} $$ is solved numerically for a region above a simulated mountain range or a semi-infinite plateau wherez is the altitude. The effect of pollution below an inversion can be included by using different values ofλ 0 and β below and above the inversion. As would be expected, theresults show that in a simple exponential atmosphere the potential increases more rapidly above the peak than avove the plain far from the mountain range. However, if a polluted inversion layer is present below the peak then the increase in the electric potential may be greater immediately above the plain than above the mountain peak which protrudes above the pollution layer. From these solutions values of the vertical and horizontal electric fields and the enhanced current density at the peak can be caculated.

Nonlinear Field Dependence of Electric Conductivity above the Superconducting Transition

Abstract: The nonlinear field dependence of the so-called anomalous term in the electric conduc­ tivity due to the fluctuation of the superconducting order parameter is studied theoretically. It is found that in the limit of a large electric field E (i.e. E'J:>Ec= y3/D s0(T)312je where c0 (T) =8/n(T-Tc) and D is the diffusion constant), the anomalous term becomes twice as large as the Aslamazov-Larkin term independenct of the dimensionality of the system and independ~nt of the pair-breaking parameter iJ.

Optical switching and video devices using organo-substituted carboranes

Abstract: Optical switching and video devices using organo-substituted carboranes are disclosed. These devices comprise a pair of transparent electrodes containing an organo-substituted carborane between them. Located on either side of the transparent electrodes are a pair of crossed polarizers. A light beam is directed toward one polarizer and emerges from the other polarizer when an electric potential is applied to the transparent electrodes. When no electric potential is applied to the transparent electrodes light is not transmitted. The color of the light transmitted or passed depends on the intensity and duration of the electric potential applied.

Print-out elements and methods using photoconductors and polygnes

Abstract: Print-out elements and methods are described which involve a crystalline polyacetylenic compound in, or in contact with a photoconductive layer. Visible images are obtained with these layers in contact by imagewise exposure coupled with the application of an electric potential. In the absence of an applied potential, the elements described are stable under normal room-light handling conditions.