Theory Of Electron Emission Research Articles

Current-field characteristics of AlAl 2O 3Al sandwiches in the regions of thermionic and T- F emission

On the basis of the earlier proposed theory of electron emission in insulators more detailed expressions for the current density in the thermionic and thermionic-field region are developed under the assumption of a Schottky image potential barrier near the metal-insulator interface. Current-field characteristics of AlAl 2O 3Al sandwiches with relatively thick oxide layers (50–150 Å) have been measured at suitable applied voltages. Rather good quantitative agreement between theoretical equations and experimental data is found.

Theory of photo-field electron emission from metal surfaces: A M Brodskiy et al,Vestn Mosk Univ Fiz Astronom, 12 (1), 1971, 11–17 ( in Russian)

Theory of photo-field electron emission from metal surfaces: A M Brodskiy et al,Vestn Mosk Univ Fiz Astronom, 12 (1), 1971, 11–17 ( in Russian)

255. General threshold theory of electron emission from the surface of a metal: A M Brodskii et al, Phys Stat Sol, 40 (1), July 1970, 139–151

255. General threshold theory of electron emission from the surface of a metal: A M Brodskii et al, Phys Stat Sol, 40 (1), July 1970, 139–151

Theory of electronic emission in a strong electromagnetic field

The threshold theory of emission phenomena, previously developed by the authors, is generalized to the case of electronic emission in the strong field of an electromagnetic wave.

General Threshold Theory of Electronic Emission from the Surface of a Metal

AbstractA unified theory of field‐, thermo‐, and photoemission from metal surface is considered, and the general quantum‐mechanical methods for the investigation of the threshold phenomena are applied. As result the corresponding final expressions are obtained in such a form that it is possible to apply immediately the well known methods of scattering theory for their investigation. Thus, a rigorous foundation for existing formula of emission phenomena is given leading to a more exact form and to restrictions of the frames of their applicability without using any concrete model. Some explanations of the emission phenomena which by traditional theory could not be explained, are suggested. Beside this the new approach to emission phenomena permits further generalization.

On the experimental proof of the general theory of electron emission from metals

A comparison is made between the recently developed general theory of thermionic and field emission from metals and the available experimental data related to the dependence of the electron emission current on both temperature and field (Andreev, Dyke et al., Drechsler, Haag). It is shown that the measurements at relatively strong currents agree well with the theoretical equations in rather wide temperature and field ranges while those at very weak currents are not reliable to be a test of the theory.

Remarks on the kinetic ejection of electrons from a copper monocrystal by argon ions with energy 20–80 keV

The regular lattice structure is introduced in Parilis' theory of electron emission by considering the “shadow” behind surface atoms. The energy dependence of the widths of the minima in δ(ψ) curves (ψ is bombarding direction) is ∝ E− 1 4 , in accordance with experiments.

Unified Theory of Thermionic and Field Emission from Semiconductors

AbstractThe recently developed general theory of electron emission from metals is extended to semiconductors assuming an arbitrary position of the Fermi level at the surface, and a parabolic energy‐momentum relation with an electron effective mass differing from the free electron mass. The expressions obtained for the emission current density from the conduction band are valid for all emission condition between the limits of thermionic and field emission. The formulae for the current originating from the valence band apply to wider emission conditions than those proposed in earlier work.

1664. The present state of the theory of secondary electron emission: V Malat, Czech J Phys, A16(6), May 1966, 242–250 (in Czech.)

1664. The present state of the theory of secondary electron emission: V Malat, Czech J Phys, A16(6), May 1966, 242–250 (in Czech.)

General Theory of Electron Emission from Metals

AbstractA theory of the emission of electrons from metals is developed on the basis of a general integral expression for the total transmission probability of an incident electron on the potential barrier at the metal surface. This integral is expressed as a sum of three conveniently defined integrals. In this way formulas are obtained for the current density for all temperature and field conditions of practical interest. The maximum error in the calculation of the total current by this method is about 10%. This theory includes as limiting cases thermionic and field emission as well as some earlier results for the emission over a narrow intermediate range of conditions. The limits of applicability of the theory in its general form are outside those of practical importance and include temperatures from 0 to 3500 °K and fields from 0 to 108 V/cm.

Thermionic Emission from Barium-coated Ultra-pure Nickel in the Emission Microscope†

Abstract After a comprehensive theory of thermionic electron emission from barium-coated alloyed nickel was established in some other place, the present investigations, using the large-screen emission microscope, served to confirm it by covering also the phenomena on polycrystalline ultra-pure nickel. Barium droplet formation was found in abundance, but of short life only. Inadequate ion densities in the contact layer are responsible for woak retaining forces, so that early evaporation leads to barium monolayer conditions without the existence of emission reversal in any instant. Hence the conclusion is drawn that the work function of ultra-pure nickel planes generally must be smaller than in the presence of abundant impurities. Poor contrast between crystal faces prevails, although very large crystal shapes emerge after rocrystallization Contrast anomaly is present but to a lesser degree than with alloyed nickel. Brief exposure to oxygen in the hot state results in a uniform and sharp increase of emissivity overruling anisotropic crystal properties Magnetic domain patterns reproduced by thermionic electrons high above the Curie point of nickel are caused by the remanent ability in the surface layer to polarize because of initial work-hardening and the directionality of the inducing magnetic lens field, particularly at the nickel surface where thermally disoriented internal lattice spins cannot cancel them fully..Removal of work hardening by excessive heating permanently cancels these fringe patterns Barium migration and evaporation mechanisms were visualized on the 21 in. screen as a dynamic streaming of barium droplets breaking loose from pools, progressively shrinking and sweeping toward hotter regions of the nickel surface.

A note on the semi-empirical theory of secondary electron emission

A note on the semi-empirical theory of secondary electron emission

Secondary Electron Emission from Clean Metal Surfaces Bombarded by Fast Hydrogen Ions

The secondary electron emission coefficient γ has been measured for clean Au, Pt, Ag, Mo, Cu, Ni, Zr, Ti and C surfaces bombarded with H1+, H2+ and H3+ ions of energies between 10 and 140 keV. Measurements of γ have been made within the monolayer adsorption time (similar 5 min) after flashing the targets to a high temperature in background pressures of approximately 10-8 mmHg. The measured values of γ intrinsic to clean metal surfaces are relatively low, e.g. γ = 1.5 for 100 keV protons incident on atomically clean molybdenum. A maximum in the yield curve for protons is found to occur in the velocity range 3 × 108-4 × 108 cm sec-1. The yield for H2+ ions is found to be almost twice that for protons at the same velocity and the yield for H3+ ions is only about 17% less than that for three protons at the same velocity. For a given ion, γ is found to vary little for the metals studied although the coefficient does increase slowly with atomic number. A few measurements involving D1+ and He+ ions show that the yield for D1+ is exactly the same as that for protons at the same velocity. The yield for He+ is approximately twice that for protons. The results are discussed in relation to a theory of secondary electron emission due to Sternglass. Partial agreement is observed.

Coherent radiation from the electrons in a synchroton:

Coherent radiation from electrons along the 10 cm wave, corresponding to the 50th harmonics of electron reverse frequency, was studied for various distributions inside the separatrix. In most cases the theory of coherent electron emission was verified. However, a deviation from theory was observed with close to uniform electron distribution. The radiation is used for measuring electron phase oscillation frequencies and the adiabatic attenuation of the amplitude of phase oscillations. The experiments were carried out with a 250-Mev betatron synchrotron. (tr-auth)

Transmission of Electrons through Metal Surfaces

This paper is a review of recent developments in the theory of electron emission from metals. The main subjects discussed are the periodic deviations in the Schottky effect and the transition between thermionic and field emission. The indications are that each of these phenomena can be understood in terms of the free electron model for the metal and the transmission of the electrons through the image force barrier at the metal surface.

High Field Conduction Currents in Hexane

The author has been able to measure conductivity currents in hexane up to the breakdown stress by using a conditioning process which enables a stable state of the electrodes and liquid to be kept for many hours. It is shown that the results are consistent with a theory of electron emission from the cathode, and that the dominant process is the Schottky one, together with the mathematically similar barrier peak tunnelling component. The work function is found to be 1.0 to 1.2 eV, although this may contain a bulk liquid component. For stresses of 1 MV cm-1 and greater, evidence is given of an ionization process within the liquid. Due to the difficulties of analysis, caused by the use of spherical electrodes, no estimate of the ionization increment factor α can be given. The tests give no information on the possibility of transient changes in the cathode state due to its inability rapidly to neutralize ionized particles reaching it.

Theory of Secondary Electron Emission by High-Speed Ions

The physical mechanism of secondary electron emission under the impact of high-speed heavy particles is analyzed. The treatment is based on the formation of secondaries according to the Bohr-Bethe theory of ionization, the diffusion of the slow secondaries to the surface, and their subsequent escape in the vacuum. The yield is found to be proportional to the rate of energy loss of the incident particles, and it is shown to be essentially the same for all metals, independent of their work function, conductivity, and other bulk properties. The observed energy distribution of the secondaries, the effect of adsorbed layers and the dependence of the yield on temperature, particle charge, and velocity are found to be explained in terms of this mechanism. The application to the general problem of the escape of electrons from metals and to the study of electron capture and loss by ions passing through solids is discussed.

Theory of Secondary Emission

The elementary theory of secondary electron emission developed by Salow, Bruining, Baroody, and others has been generalized and modified to incorporate recent measurements by Young of the range-energy relation and the dissipation of energy by slow electrons in solids. It is found that these modifications give considerably improved agreement between the theoretical and experimental universal reduced yield curves. However, for primary energies several times higher than that for which the yield has its maximum value, deviations occur; the reduced yield curve for metals appears to lie slightly above the theoretical curve, while that for MgO falls increasingly below. Similar results are found for Ge, but the agreement is better than for MgO.

Theory of Secondary Electron Emission from Solids

A formula is derived permitting the calculation of the yield of secondary electrons from the yield of photoelectrons.

The Work Function of Irregular Metal Surfaces

It is shown that the image potential of an electron outside an irregular metal surface is different from that for an ideal plane surface. Calculations of this potential for spherical and prolate spheroidal bosses on an otherwise smooth surface show that the image potential might easily be reduced by 50%. Since the image potential energy is likely to form a large portion of the work function for most metals, then the latter also will be significantly reduced when the surface is rough. The importance of this in the theory of electron emission from metals in practice is briefly discussed.