Analysis of low pressure electro-positive and electro-negative rf   plasmas with Monte Carlo method
  Particle-in-cell/Monte Carlo technique is used to simulate low pressure electro-negative and electro-positive plasmas at a frequency of 10 MHz. The potential, electric field, electron and ion density, and currents flowing across the plasma are presented. To compare the physical properties of the electro-positive gas with those of an electro-negative gas, the input voltage was decreased from 1000 Volts to 350 Volts. The simulation results indicate that the introduction of negative ions induces dramatic effects on the spatial and temporal variation of the electric field and on the behavior of the electron, ion, and displacement currents. In particular, the numerical modeling predicts the formation of double-layer at the plasma-sheath boundary of electro-negative discharge. 
M. Ardehali