A kinetic model for an argon plasma containing dust grains

Abstract

A complex low-pressure argon discharge plasma containing dust grains is studied using a Boltzmann equation for the electrons and fluid equations for the ions. Local effects, such as the spatial distribution of the dust density and external electric field, are included, and their effect on the electron energy distribution, the electron and ion number densities, the electron temperature, and the dust charge are investigated. It is found that dust particles can strongly affect the plasma parameters by modifying the electron energy distribution, the electron temperature, the creation and loss of plasma particles, as well as the spatial distributions of the electrons and ions. In particular, for sufficiently high grain density and/or size, in a low-pressure argon glow discharge, the Druyvesteyn-like electron distribution in pristine plasmas can become nearly Maxwellian. Electron collection by the dust grains is the main cause for the change in the electron distribution function.

Low‐Pressure PECVD of Nanoparticles in Carbon Thin Films from Ar/H2/C2H2 Plasmas: Synthesis of Films and Analysis of the Electron Energy Distribution Function

“…2a)). It is worth mentioning that, in reasonable agreement with measurements of T e with increasing C 2 H 2 , the values of the T e associated with the Maxwellian fits (better for 20 % C 2 H 2 ) are roughly around 1.75 eV (for 1 % C 2 H 2 ) and the more realistic 1.15 eV (for 20 % C 2 H 2 ), exhibiting a decreasing trend with growing C 2 H 2 that is probably connected with an increase of the non-uniformly distributed [25,29] dust concentration in the discharge due to the fast polymerization of C 2 H 2 in the plasma. We can see in Figures 2 and 3 that the assumption of a Maxwellian shape for the EEDF is, in general, better justified as the relative concentration of C 2 H 2 grows so that the measured T e s are closer to the calculated ones when using 20 % C 2 H 2 .…”

“…The value of the amplitude, E 0 , of the electric field is chosen following recent results on predicted values of the electric field in dusty plasmas as a function of the dust particle size. [29,30] The possible use of the QSS and/or DC effective field approximations would considerably save computation time (no timedependent Boltzmann equation would need to be solved) and simplify the study of the underlying plasma kinetics. We have chosen two values of E 0 equal to 0.60 V cm -1 and 1 V cm -1 in the plasma bulk which, according to recent results by Denysenko et al [30] for conditions quite similar to ours, are related to particle diameters of 50 nm and 200 nm, respectively.…”

Influence of the power on the particles generated in a low pressure radio frequency nitrogen-rich methane discharge

“…The particles, during their formation and growth, trap electrons with an energy higher than the particle surface potential. 35 The electron energy distribution function ͑EEDF͒ is thus depleted of these electrons. The introduction of a small quantity of argon or helium in the CH 4 / N 2 gas mixture allows us to get indications concerning the EEDF.…”

“…Nevertheless, it has been shown that the electron number density with low energy increases at the beginning of the particle formation. 35 Consequently, the CN intensity increase at the beginning of each particle generation ͑as the N 2 one͒ may also result from the EEDF modification. The excited species CN, N 2 , and N 2 + intensities may also depend on their contribution in the particle growth.…”

A non-Maxwellian kinetic approach for charging of dust particles in discharge plasmas

“…In argon the EEDF shape changes from Druyvesteyn to bi-Maxwellian with decreasing gas pressure. The dust particle charge was investigated in [3] in a low pressure argon discharge plasma using a Boltzmann equation for the electrons and fluid equations for the ions. It was found that the presence of the dust particles modifies the shape of the EEDF from Druyvesteyn to Maxwellian due to the fact that the dust grains collect fast electrons.…”