Plasma-sheath resonances and energy absorption phenomena in capacitively coupled radio frequency plasmas. Part I

Abstract

A plasma-sheath resonance has been observed at low pressures in argon plasmas. This phenomenon was known in a different context, that of the plasma resonance probe, but was hitherto unknown in parallel-plate plasma reactors. Two different models have been used to resolve the plasma-sheath resonances. A simple linear model is used to represent the plasma system as a series circuit of two capacitors (sheaths) and an inductor (plasma region). The plasma-sheath resonance occurs at a frequency where the cold plasma behaves inductively and resonates together with the two sheaths. The second model treats the plasma bulk as a series combination of an infinite number of elementary cells each one constituted by an inductor and a capacitor in parallel. By assuming an electron density profile the total impedance of the plasma can be obtained. Furthermore, the calculations show that the resonant energy is absorbed at an infinitely thin resonance plane. This causes the impedance of the system, filled with a lossless inhomogeneous plasma, to have a real part. This resonance can be used as a diagnostic, to measure the electron density. It could perhaps be exploited as the basis of a new plasma reactor.

Modeling of microplasmas from GHz to THz

“…3,4 The previous explanations used averaged quantities as presented in Figure 1. Next, we present the internal details of the spatial and temporal variation of current.…”

“…These resonant behaviors of the plasma have been intensively investigated over the years [3][4][5][6][7][8][9] (a brief chronological review is made in Ref. 3). Most of the recent work concerns the series resonance in low pressure discharges and is motivated by its applicability to the plasma processing industry.…”

“…3. That approach identifies two resonant interactions involving the inductance of the quasineutral bulk plasma.…”

“…The series resonance occurs at a lower frequency related to the plasma frequency through a geometric factor involving the sheath thickness (s) and plasma length (L), x $ x p ffiffiffiffiffiffiffi s=L p . These resonant behaviors of the plasma have been intensively investigated over the years [3][4][5][6][7][8][9] (a brief chronological review is made in Ref. 3).…”

Antenna Impedance Measures in a Magnetized Plasma. Part 1. Spherical Antenna

“…Most of this research was for spacecraft and rocket mounted plasma diagnostics for electron density measurements in the ionosphere. Recently, there has been renewed interest in this subject as advances in measurement and computer technology have allowed scientists to collect more accurate readings and model antennas more realistically than was previously possible [9]- [18]. The use of impedance measurements for space physics research is still a fairly active field, but there have also been new applications; for example, plasma electron density measurements under experimental conditions that make it difficult to get Langmuir probe readings, such as plasma thrusters [11] and processing plasmas [14].…”