Floating potential in a bi-Maxwellian RF plasma

The floating potential is investigated for a planar probe/electrode in a DC/RF plasma with a bi-Maxwellian electron distribution. A form of Bohm velocity is adopted appropriate to a two-temperature ( T 1 , T 2 ) plasma with corresponding electron densities n 1 , n 2 . Taking hydrogen as an example, a numerical study shows that for given values of T 1 / T 2 , n 1 / n 2 and RF amplitude (normalized to T 1 ), the floating potential (normalized to T 1 ) is unique. On the other hand, using the same normalizations for prescribed values of floating potential and RF amplitude, and given n 1 / n 2 , there are two values of T 1 / T 2 . Conversely for given values of floating potential, RF amplitude and T 1 / T 2 , n 1 / n 2 may be single or double valued. Under conditions of sheath inversion RF plasmas again show uniqueness or two valuedness, according to the prescription.