Electron transport coefficients in dusty argon plasmas

Abstract

Low-temperature partially ionized plasmas, as used in plasma processing reactors and gas lasers, are often contaminated by gas phase particulates (1–10’s μm radius) resulting from electrode sputtering or gas phase chemical reactions. Particles having sizes comparable to or greater than the Debye length will negatively charge in the plasma and form a sheath at their surfaces. These particles thereby become a Coulomb-like scatterer of electrons. A hybrid Monte Carlo/molecular dynamics computer simulation has been developed to study the effect of such particulate contamination on electron transport in glow discharges and this letter presents results for argon. The dominant effect of particulate contamination is to shift the electron energy distribution to lower energies, thereby reducing electron impact rate coefficients for processes which have high threshold energies, particularly ionization. The self-sustaining E/N of discharges having dusty plasmas is therefore increased. The effect, proportional to particle density, begins to become important at a density of 103–105 cm−3 for gas pressures of 0.1–3 Torr.