A particle-in-cell simulation of the breakdown and period doubling thresholds for a RF discharge Ar plasma

RF glow-discharge plasmas provide mild energetic ion bombardment of exposed surfaces. The characteristics of a 10 MHz RF glow-discharge Ar plasma are studied by particle-in-cell simulation. The model simulates a spherical plasma device using a one-dimensional plasma model. The code is used to determine the breakdown voltage, Vrf , for a given pd , where p is the gas pressure and d is the plasma discharge length. These values are then compared with Paschen’s law for the DC case. Also, the breakdown voltage as a function of driver frequency is investigated. Due to the nonlinear capacitance of the plasma, the current and voltage waveforms are found to contain higher harmonic components and sub-harmonic components. Above a certain power level of the driver, sub-harmonics which are indicative of a period-doubling (PD) bifurcation are found to become dominant. The PD thresholds for varying pd , the magnitude of the current and the voltage of the Fourier-analysed components as a function of applied RF voltages are calculated. The PD threshold is always higher than the breakdown threshold. Finally, the pressure-dependence of the sheath width is discussed.