What hardware is used to generate plasma?
One must apply an electrical field to the gas to generate a plasma. In a vacuum chamber, where the ions and electrons have long lifetimes, it is relatively easy to do this. Radio frequency power can be applied to two metal plates immersed in the vessel creating a capacitive discharge. Alternatively, RF power may be deposited into a coil mounted on the chamber walls, thereby producing an inductively coupled plasma. The gas also may be ionized by application of microwave power at 2.45 GHz to a specially designed cavity or horn. In an atmospheric plasma, a variety of power supplies may be used from DC to RF. Here, the challenge is to design the electrodes and gas flow to yield intimate contact between the reactive gases and the substrate. At high pressure, the atoms and radicals are quickly consumed by collisions in the gas, so the transit time from the plasma to the surface must be short. If one wishes to achieve low temperature operation with atmospheric plasmas, then special precaution
