Ion energy distribution functions behind the sheaths of magnetized and non magnetized radio frequency discharges

TL;DR

This paper investigates how magnetic fields influence ion energy distributions and asymmetries in radio frequency discharges, revealing indirect effects on sheath conditions and demonstrating simulation methods' effectiveness.

Contribution

It demonstrates that magnetic fields can induce asymmetries in RF discharges and affect ion energy distributions indirectly, supported by particle-in-cell and ensemble-in-spacetime simulations.

Findings

Magnetic fields cause asymmetry in symmetric discharges.

Ion energy distributions are strongly affected by magnetic fields.

Ensemble-in-spacetime algorithm accurately reproduces ion energy distributions.

Abstract

The effect of a magnetic field on the characteristics of capacitively coupled radio frequency discharges is investigated and found to be substantial. A one-dimensional particle-in-cell simulation shows that geometrically symmetric discharges can be asymmetrized by applying a spatially inhomogeneous magnetic field. This effect is similar to the recently discovered electrical asymmetry effect. Both effects act independently, they can work in the same direction or compensate each other. Also the ion energy distribution functions at the electrodes are strongly affected by the magnetic field, although only indirectly. The field influences not the dynamics of the sheath itself but rather its operating conditions, i.e., the ion flux through it and voltage drop across it. To support this interpretation, the particle-in-cell results are compared with the outcome of the recently proposed ensemble-in-spacetime algorithm. Although that scheme resolves only the sheath and neglects magnetization, it is able to reproduce the ion energy distribution functions with very good accuracy, regardless of whether the discharge is magnetized or not.