Field-Induced and Thermal Electron Currents from Earthed Spherical Emitters

Holgate, Joshua; Coppins, M.

doi:10.1103/physrevapplied.7.044019

Cited by 22 publications

(8 citation statements)

References 41 publications

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“…In the calculation, for each dc field, the effective work function is approximated by determining the peak value in the surface barrier profile under dc [43,44], Φ In /In 1 /2 , where the second term is the axial potential profile near a parabolic tip of radius of curvature r with d being a constant (= 83 nm to fit the spectra in Fig. 10(a)) [44], and the third term is the image charge potential of a spherical surface, with /4 1.199985 eV V/nm / being the Schottky constant [43]. It is important to note that the photoelectron spectra is very sensitive to the applied dc field , as shown in Figs.…”

Section: Application To Time-resolved Photoelectron Spectroscopymentioning

confidence: 99%

Analysis of two-color laser-induced electron emission from a biased metal surface using an exact quantum mechanical solution

Luo

Zhang

2019

Phys. Rev. Applied

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Photoelectron emission from solids driven by high intensity lasers offers a platform for the coherent control of electron motion in ultrashort spatiotemporal scales. By solving the time-dependent Schrödinger equation, we present an exact analytical solution for the nonlinear ultrafast electron emission from a dc biased metal surface illuminated by two-color laser fields. We systematically examine the combined effects of a dc electric field and the two-color laser fields. In addition to the remarkable tunability of electron emission processes due to the interference of the two-color laser fields, we find that a strong dc electric field not only opens up more tunneling emission channels, but also introduces intense modulation to the emission current. We found the surprising results that strong current modulation (with respect to the phase difference of the two-color lasers) persists (>70%) even with a large dc bias (i.e. ratio of the electric fields for dc : fundamental laser : second harmonic laser 1 : 0.5 : 0.07). In the meantime, the average emission current level increases by about three orders of magnitude compared to the case of zero dc bias. Application of our model to time-resolved photoelectron spectroscopy is exemplified, showing the dynamics of the n-photon excited states depends strongly on the applied dc field. Our study suggests a practical way to maintain a strong modulation to high current photoemission, by the addition of a large dc bias for two-color laser induced electron emission.

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Section: Application To Time-resolved Photoelectron Spectroscopymentioning

confidence: 99%

Analysis of two-color laser-induced electron emission from a biased metal surface using an exact quantum mechanical solution

Luo

Zhang

2019

Phys. Rev. Applied

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“…Finally, Kyritsakis & Xanthakis [7,8] have derived-starting from the original WKB expression-a generalized FN equation for an arbitrary emitter of radius of curvature R > 5 nm in which the corrections to the planar FN theory appear both in the exponential Gamow term and the pre-exponential factor. Their equation was shown to be verified by data from three separate experimental groups and by a recent analytical work by Holgate & Coppins [9]. Furthermore, from the curvature of the equation of Kyritsakis & Xanthakis [7] the value of the experimental R could be deduced, as is, indeed, possible from the work of Edgcombe & de Jonge [4].…”

Section: Introductionmentioning

confidence: 64%

Exact eigenstates of a nanometric paraboloidal emitter and field emission quantities

Chatziafratis¹,

Fikioris²,

Xanthakis³

2018

Proc. R. Soc. A.

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The progress in field emission theory from its initial Fowler-Nordheim form is centred on the transmission coefficient. For the supply (of electrons) function one still uses the constant value due to a supply of plane-waves states. However, for emitting tips of apex radius of 1-5 nm this is highly questionable. To address this issue, we have solved the Schrödinger equation in a sharp paraboloidally shaped quantum box. The Schrödinger equation is separable in the rotationally parabolic coordinate system and we hence obtain the exact eigenstates of the system. Significant differences from the usual Cartesian geometry are obtained. (1) Both the normally incident and parallel electron fluxes are functions of the angle to the emitter axis and affect the emission angle. (2) The WKB approximation fails for this system. (3) The eigenfunctions of the nanoemitter form a continuum only in one dimension while complete discretization occurs in the other two directions. (4) The parallel electron velocity vanishes at the apex which may explain the recent spot-size measurements in near-field scanning electron microscopy. (5) Competing effects are found as the tip radius decreases to 1 nm: The electric field increases but the total supply function decreases so that possibly an optimum radius exists.

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“…The emitted current density of electrons from the surface is highly sensitive to the local surface field strength which is itself strongly enhanced by the high curvature of small irregular features on the surface. 30,31 The large emitted electron current from these small irregular features is an important trigger for the formation of unipolar arc spots which are believed to provide a significant source of droplets which contaminate and degrade the plasma of magnetic confinement fusion devices. 32,33 The increase in electric field strength at a surface protrusion can be quantified with field-enhancement factors which give the ratio of the surface field strength at the curved feature to the field strength for a perfectly flat surface under the same conditions.…”

Section: B Sinusoidal Cathodementioning

confidence: 99%

Numerical implementation of a cold-ion, Boltzmann-electron model for nonplanar plasma-surface interactions

Holgate

Coppins

2018

Physics of Plasmas

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Plasma-surface interactions are ubiquitous in the field of plasma science and technology. Much of the physics of these interactions can be captured with a simple model comprising a cold ion fluid and electrons which satisfy the Boltzmann relation. However, this model permits analytical solutions in a very limited number of cases. This paper presents a versatile and robust numerical implementation of the model for arbitrary surface geometries in cartesian and axisymmetric cylindrical coordinates. Specific examples of surfaces with sinusoidal corrugations, trenches, and hemi-ellipsoidal protrusions verify this numerical implementation. The application of the code to problems involving plasma-liquid interactions, plasma etching, and electron emission from the surface is discussed.

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Field-Induced and Thermal Electron Currents from Earthed Spherical Emitters

Cited by 22 publications

References 41 publications

Analysis of two-color laser-induced electron emission from a biased metal surface using an exact quantum mechanical solution

Analysis of two-color laser-induced electron emission from a biased metal surface using an exact quantum mechanical solution

Exact eigenstates of a nanometric paraboloidal emitter and field emission quantities

Numerical implementation of a cold-ion, Boltzmann-electron model for nonplanar plasma-surface interactions

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