Plasma sheath model and ion energy distribution for all radio frequencies

The spatiotemporal structure of the sheath and the ion energy distribution (IED) at the electrode of a collisionless electropositive glow discharge were studied with a model that is valid for arbitrary radio frequencies (rf). The model is based on the work of P. A. Miller and M. E. Riley [J. Appl. Phys. 82, 3689 (1997)] and uses an effective electric field to which the heavy ions respond. Given the plasma density and electron temperature at the sheath edge, and the waveform of either the potential or total current across the sheath, the spatial and/or temporal profiles of the following quantities were obtained: sheath thickness and capacitance, electron and ion densities, potential, and individual components of the current. An analytic expression for the energy split of the IED function was also obtained. The product omega tau(i) of applied radian frequency omega and ion transit time tau(i) is a critical parameter for describing the sheath dynamics. (C) 1999 American Institute of Physics. [S0021-8979(99)02207-0].