Effect of adding small amount of inductive fields to O2, Ar/O2 capacitively coupled plasmas

Electron energy distribution functions (EEDFs) of low pressure O-2 plasma were measured by adding small amount of coil power in a capacitive discharge. When the plasma was generated by bias power only, the measured EEDF showed a bi-Maxwellian distribution. However, when a very small coil power (a few Watts) was added, the EEDF evolved abruptly into a Maxwellian distribution, while the electron density was decreased. In an Ar/O-2 mixture discharge, this EEDF evolution to the Maxwellian was also observed at a relatively higher coil power. This abrupt change in EEDFs with a very small coil power appears to be attributed to a combined effect of collisionless heating by capacitive and induced electric fields. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4705362]