Parameter space for collisionless RF sheaths

As plasma processing reactors approach higher density, the sheath models which neglect the radio frequency (RF) response of the ions become invalid. This work show that the nature of the collisionless RE ion sheath can be described in a number of different regimes of parameter space. These regimes can all be visualized on a single two-dimensional (2-D) plot where the horizontal axis is the ion plasma frequency divided by the frequency, and the vertical axis is the electron oscillating velocity divided by the ion sound speed.