Hysteresis induced by gap length effects in capacitively coupled plasmas at low pressures

Gap length effects on the properties of capacitively coupled plasmas at low pressures are investigated with particle-in-cell/Monte Carlo simulations. A hysteresis, or two different steady states under the same parameters, in argon gas is observed for the first time. Simulation results show that the hysteresis may be a consequence of different energy diffusion coefficients. At smaller gaps, electron energy probability functions will have much higher energy tails, and the average electron energy loss to the electrodes will increase significantly. These imply the electrons are possibly heated by the resonance heating mechanism and therefore electron energy probability functions are anisotropic.