A comparison of a Langmuir probe technique with an emissive probe technique to measure the plasma potential in a RF plasma

Abstract

Summary form only given, as follows. In a RF plasma, the plasma potential can be fluctuated with time and both Langmuir and emissive probes measurements are based on the time-averaged characteristic I-V curves. Hence the inflection points in the derivative of I-V curve represents the peak to peak plasma potential fluctuation. The estimated plasma potential by Langmuir probe technique tends to be underestimated because of the electron kinetic energy (electron temperature). However the plasma potential can be determined more precisely when an emissive probe is used with the inflection point method in the limit of zero emission. In this experiment, the potential differences determined by two probe techniques are quantitatively estimated as a function of the electron temperature. The electron temperature of an inductively coupled plasma was controlled by the gas pressure. The measurement of plasma potential in Langmuir probe is carried out from the numerically filtered data by the Bi-orthogonal wavelet filtering method (the related study is present in this conference). The geometry effects of Langmuir probe in the plasma potential measurement also have been investigated.