30 th ICPIG, August 28 th - Septemper 2 nd , 2011, Belfast, UK Topic number A4 Current-Voltage characteristics of nonharmonically modulated plasma boundary sheaths Abd Elfattah T. Elgendy , D. Eremin , T. Mussenbrock , Ralf Peter Brinkmann Institute for Theoretical Electrical Engineering, Ruhr University Bochum, Bochum, Germany Abstract: The dynamics of dual frequency capacitive RF discharges is largely dominated by the charge-voltage characteristics of the plasma boundary sheath, which in turn is dependent on the characteristcs of the modulation. This contribution focuses on the behavior of the sheath under nonharmonic excitation, such as square, sawtooth, dual frequency and pulse-like excitation. Fluid model of a collisional sheath and a PIC simulation of different complexety and computational efficiency is established and compared. 1. Introduction: Plasma technology is applied in many areas that require high quality and precision demands. It is especially important in areas such as manu- facturing of semiconductors, solar cells, textile, medical technologies,etc. Capacitively coupled plasmas (CCPs), are widely used for material processing. In recent years it was realized that further improvement of plasma processes cannot be achieved without an improved insight in their functioning. The sheath controls the energy and angular distribution of the ions, efficiency of the energy coupling and characteristics of the non- linear behavior. Theoretical and experimental perspectives be studied. [1–8]. In this work the driving different RF excitations frequency will invesigate in details based on exact model and PIC simulation, in its collision form. The result of different characteristic behaviour of sheath plasma such as density of ion and electron distribution, electric field, sheath charge, current distribution and V (Q) - Q characteristics curve will study. 2. collisional sheath model 2.1. RF modulated boundary sheath The behavior of capacitive RF discharges is largely determined by the boundary sheath. In particular, the sheath controls the energy and angular distribution of the ions, efficiency of the energy coupling, as well as characteristics of the nonlinear behavior. n e n i n e t st x a.u. n a.u. Fig. 1: Schematic picture of electron and ion density in an RF modulated sheath. 2.2. Fluid model of the collisional sheath Ion model Stationary, phase averaged ion dynamics describ- ing with n i v i = ψ i (1) 0= en i ¯ E - π 2 m i n i v i |v i | λ i (2) Connection of the instantaneous to the phase averaged field ¯ E = 1 T  T 0 E(x,t)dt Electron dynamic model The electrons in contrast follow the instantenaous E field, we assumed that (Boltzmann equilibrium) T e ∂n e ∂x = -en e E (3) Possion Equation The instantenaous electric field is qusiataic to the