Dielectric properties in microwave remote plasma sustained in argon: Expanding plasma conditions

Abstract

This work is devoted to the study of the relative permittivity in argon expanding plasma produced below a microwave discharge sustained in a quartz tube and working at 2.45 GHz. We discuss results and explain the microwave propagation within the reactor, outside the quartz tube. It is shown that at low pressures (133 Pa) and at powers ranging from 100 W to 400 W, the wave frequency remains lower than the plasma frequency anywhere in the expanding plasma. Under these conditions, the real part of the relative permittivity is negative and the wave is reflected. Surprisingly, in these conditions, the plasma is produced inside and outside the quartz tube, below the wave launcher. This effect can be explained considering a surface wave propagating at the surface of the quartz tube then into the reactor, on the external surface of the expanding plasma below the quartz tube. V

A global model of cylindrical and coaxial surface-wave discharges

“…The negative ion loss mechanism is dominated by the detachment as expected in the considered pressure regime [38]. A hypothetical inclusion of an axial ion edge-to-centre ratio, for example, with the critical edge electron density of the surface-wave propagation [55], are negligible on the results.…”