Effect of helium on spatial plasma parameters in low pressure argon-helium plasma

Spatial distributions of the electron energy probability function were measured using a Langmuir probe in side-type argon-helium inductively coupled plasma. Collisional dominated electron heating and a concave shape of plasma density profile were observed at 10 mTorr pure argon. As the helium proportion increased, the electron heating and density profile changed to collisionless dominated heating and a convex shape respectively, and the same tendency was shown when the pressure decreased in the pure argon plasma. These changes were due to the decrease in the e-n collision frequency and the expansion of the electron power dissipation region. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.3703608]//dx.doi.org/10.1063/1.3703608