Electronic Processes at the Carbon-Covered (100) Collector Tungsten Surface

We have performed density functional VASP calculations of a pure and of a carbon-covered (100) tungsten surface under the presence of an electric field E directed away from the surface. Our aim is to answer the question of an increased penetrability of electrons at the collector side of a nanometric...

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Bibliographic Details
Published in:Micromachines (Basel) 2022-05, Vol.13 (6), p.888
Main Authors: Gotsis, Harilaos J., Bacalis, Naoum C., Xanthakis, John P.
Format: Article
Language:English
Subjects:
Boundary conditions
Carbon
carbon-covered tungsten surface
Density
Electric fields
Experiments
Field emission microscopy
Mathematical analysis
Potential energy
Quantum mechanics
Scanning field emission microscopy
scanning microscopy
Straight lines
Tungsten
tunnel diode
Tunnel diodes
VASP calculation
workfunction
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Summary:We have performed density functional VASP calculations of a pure and of a carbon-covered (100) tungsten surface under the presence of an electric field E directed away from the surface. Our aim is to answer the question of an increased penetrability of electrons at the collector side of a nanometric tunnel diode when covered by carbon atoms, a purely quantum mechanical effect related to the value of the workfunction Φ. To obtain Φ at a non-zero electric field we have extrapolated back to the electrical surface the straight line representing the linear increase in the potential energy with distance outside the metal-vacuum interface. We have found that under the presence of E the workfunction Φ = Evac − EF of the (100) pure tungsten surface has a minor dependence on E. However, the carbon-covered tungsten (100) surface workfunction Φ(C − W) has a stronger E dependence. Φ(C − W) decreases continuously with the electric field. This decrease is ΔΦ = 0.08 eV when E = 1 V/nm. This ΔΦ is explained by our calculated changes with electric field of the electronic density of both pure and carbon-covered tungsten. The observed phenomena may be relevant to other surfaces of carbon-covered tungsten and may explain the reported collector dependence of current in Scanning Field Emission Microscopy.
ISSN:2072-666X
2072-666X
DOI:10.3390/mi13060888