  Macroscopic objects floating in an ionized gas (plasma walls) accumulate
electrons more efficiently than ions because the influx of electrons outruns
the influx of ions. The floating potential acquired by plasma walls is thus
negative with respect to the plasma potential. Until now plasma walls are
typically treated as perfect absorbers for electrons and ions, irrespective of
the microphysics at the surface responsible for charge deposition and
extraction. This crude description, sufficient for present day technological
plasmas, will run into problems in solid-state based gas discharges where, with
continuing miniaturization, the wall becomes an integral part of the plasma
device and the charge transfer across it has to be modelled more precisely. The
purpose of this paper is to review our work, where we questioned the perfect
absorber model and initiated a microscopic description of the charge transfer
across plasma walls, put it into perspective, and indicate directions for
future research.
