Presence Of High Electric Field Research Articles

An instrument for measuring the tensile properties of powders at elevated temperature and in the presence of electric fields

A new method is described for measuring the tensile strength of weak powder compacts by applying stress to a vertical powder test piece, formed and supported by the glass and metal surfaces of a split cell. Tension is applied by slowly stretching a long vertical spring to which the upper powder support is attached, until brittle fracture occurs at the unsupported waist of the test piece. Tensile strength is calculated from the spring elongation at fracture. The instrument is designed to measure tensile strengths in the range 10-2000 N m-2 at temperatures up to 200 degrees C. There are two modes of operation for separate or joint determination of shear and tensile properties. The ability to function in the presence of high electric fields (up to 2 kV mm-1) is an additional feature of the equipment.

Chemical surface reactions in the presence of high electric fields

Abstract Since the invention of the field ion microscope (FIM) by E. W. Muller1 and the first mass-spectrometric analysis of field ions by Inghram and Gomer,2 these tools for field ionization have been developed considerably, as described in several monographs and summarizing artilces.3–8 Field ion mass spectrometry (FIMS) can analyze solid surfaces with extreme sensitivity. The experimental facilities enable ultimately the identification of single surface particles, which can be correlated to individual surface sites within the atomic scale of a surface. The atom-probe, which was developed by E. W. Muller,9 can now analyze surface particles with high precision in mass resolution.

The activation energy for surface self-diffusion of tantalum and the influence of residual gases on this quantity in the presence of high electric fields

When tantalum field emission microscope tips are heated in the presence of applied electric fields, the build-up of the 〈111〉 areas dominates. A linear relationship is indicated between the activation energy for surface self-diffusion, Q F, determined from this process and log p ( p average residual gas pressure during the measurement). The negative slope is interpreted in terms of the presence of a permanent dipole migration mechanism. At p=5×10 −10Torr and F apex=22 MV/cm, Q F≅1.4 eV/particle. From the build-up decay the corresponding activation energy for surface self-diffusion without applied field Qs=2.03±0.05 eV/particle could be determined. The higher values obtained by other authors are explained by the influence of contaminants.

The influence of residual gases and oxygen on the activation energy for surface self-diffusion of tungsten in the presence of high electric fields

Two build-up stages could be distinguished during the heating of tungsten field emitters at various residual gas pressures, p, while an electric field, F, was applied: (a) build-up around the 〈111〉 poles and (b) build-up around {100} planes. A plot of log p versus Q F, the activation energy for surface self-diffusion with field, indicated a linear relation with a positive slope for {100} build-up and a linear relation with a negative slope for 〈111〉 build-up. The value of Q F also, is a linear function of F, indicating a permanent dipole migration mechanism. In the presence of oxygen, 〈111〉 build-up occurred predominantly. The Q F values match the pressure dependence for residual gas 〈111〉 build-up. It could be determined: Q F (W-atom) = 1.9 eV/particle for F = 25 MV/cm , Q F = 0 (dipole) = 4.8 eV/particle at P residual = 4 × 10 −9 Torr, and an effective dipole moment of μ ⋍ 6 D . The increase of Q F {100} with increasing residual gas pressure is proposed to be due to pinning by carbon. The final build-up form ({110}, {100}, and {112}) is discussed in comparison with other single-crystal growth forms of tungsten.

Microwave Conductivity of n-Type Germanium in the Presence of High Electric Field

Microwave Conductivity of n-Type Germanium in the Presence of High Electric Field

High Field Transport Phenomena in n-InSb at High Temperatures

Earlier theories of transport phenomena in n -InSb have been extended to include medium-high electron concentrations at high lattice temperatures (300° to 500°K) in presence of high electric fields. Polar optical mode of electron-phonon scattering has been considered to be the sole mechanism of electron scattering at these temperatures. The steady state electron distribution function has been chosen to be the Fermi-Dirac distribution function appropriate to the effective electron temperature which is determined by the energy balance condition. Nonparabolicity of the conduction band has been taken care of by the Kane's model. It is seen that the effective electron temperature is not far above the lattice temperature even at the highest attainable fields and that the Galvano-thermo-magnetic transport coefficients do not exhibit any marked dependence on the strength of electric field under the present conditions. Some limitations and approximations have also been mentioned.

Metal-glass contacts in high electric fields

In the presence of high electric fields, the region adjacent to a metallic anode of an ionic conducting glass quickly becomes depleted of mobile ionic carriers. At the cathode, however, electrons are injected into the glass from the metal electrode and cause the effective conductivity of this region to increase.

Microwave conductivity of polar semiconductors in the presence of high electric field

The frequency-dependent small-signal conductivity of polar semiconductors in the presence of high steady electric field is calculated theoretically taking into consideration both the momentum and energy relaxation times. The results obtained are compared with experiments carried out on InSb.

Experimental study of the phenomena associated with the presence of high electric fields in the thin insulating films : J. Lebrun, L'Onde Electrique, pp. 1022–1039 (Oct. 1963). (In. French.)

Experimental study of the phenomena associated with the presence of high electric fields in the thin insulating films : J. Lebrun, L'Onde Electrique, pp. 1022–1039 (Oct. 1963). (In. French.)