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 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.

Non-topographic current contrast in scanning field emission microscopy.

In scanning field emission microscopy (SFEM), a tip (the source) is approached to few (or a few tens of) nanometres distance from a surface (the collector) and biased to field-emit electrons. In a previous study (Zanin 2016 , 20160475. (doi:10.

Exact eigenstates of a nanometric paraboloidal emitter and field emission quantities.

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.

Beam spot diameter of the near-field scanning electron microscopy.

We have examined the beam spot diameter at the anode of the scanning electron microscopy (SEM) in the near-field mode as a function of the anode-tip distance d. The detector lateral resolution of this type of microscopy is approximately equal to this spot diameter. For our calculations we have simulated the apex region of the tip with an ellipsoid of revolution of radii R₁ and R₂ with R₁>R₂ as suggested by TEM images of the realistic tips.