Influence of Plasma-Neutral Collisions on Probe Measurements in Atmospheric Pressure Plasmas



We report on the influence of plasma-neutral collisions in the sheath in front of a probe electrode based on the results of particle-in-cell simulations. The simulated space potential profiles indicate that the sheath potential drops with increasing neutral gas pressure Pn. According to collisionless theory, the apparent electron temperature is three times higher than that corresponding to the collisionless case at Pn = 0.1 Torr. To explain the deep negative potential at high Pn, the ion reduction factor β for the ion flux is proposed. It is found that β is related to the increased potential drop, however, it is difficult to explain the simulation results quantitatively when only elastic collision between ions and neutral particles are taken into account. (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)