What is downstream plasma?

[hoegs]

Downstream plasma treatment is often called “ion-free” plasma as it
utilizes only the radical species generated within plasma discharge.

A plasma discharge containing electrons, ions, and radicals is
generated upstream between a powered and ground electrode.

The sample is located downstream of the glow discharge, and is
typically placed on a floating electrode.

The active species in the plasma diffuse to the sample by passing
through a perforated ground electrode.

The perforated ground electrode removes the ions and electrons from the
gas stream while permitting the radicals to diffuse to the sample.

The plasma treatment is a result of the interaction of the radical
species with the sample surface.