Image charge force of keV ions through insulating nanocapillaries

Eric Giglio (1, 2)

1 SIMUL - Simulation
2 CIMAP - UMR 6252 - Centre de recherche sur les Ions, les MAtériaux et la Photonique

In nanocapillaries of large aspect ratio, the attractive image charge force is strong enough to affect the trajectory of ions passing through capillaries and consequently to diminish the fraction of transmitted beam ions. We calculated the theoretically transmitted fraction, using an expression of the image charge force valid in the case of a static ion and an infinite cylindrical dielectric interface. When comparing the theoretically transmitted fraction to the available experimental data for nanocapillaries with an inner diameter of less than 200 nm, we found a surprisingly large disagreement, i.e., the theoretically transmitted fractions were easily an order of magnitude lower than the experimental ones. Noting that the image charge force depends on the velocity of the ion via the frequency-dependent relative permittivity of the insulator, we investigated whether the disagreement could be lifted using a velocity depend image charge force. We give the exact expressions of the dynamical image charge force for a plane and cylindrical dielectric interface as a function of the ion velocity. We then reevaluated the theoretically transmitted fractions in the case of SiO$_2$ and polyethylene terephthalate dielectric interfaces. Our findings are discussed in light of the available experimental data.

Keywords: capillary; secondary electrons; ion beam

Domains: Physics [physics]

Eric Giglio. Image charge force of keV ions through insulating nanocapillaries. Physical Review A, 2023, 107, pp.012816. ⟨10.1103/PhysRevA.107.012816⟩. ⟨hal-04312990v2⟩