Power transfer efficiency and the power threshold for E–H mode transition in inductively coupled plasmas

Abstract

The effects of gas pressure and gas component on the power transfer efficiency [Formula: see text] and transition power threshold [Formula: see text] during the E–H mode transition in inductively coupled plasmas are studied. The evolutions of [Formula: see text] during the E–H mode transition in pure Ar and Ar/O2 discharges are similar, i.e., in E-mode discharge, [Formula: see text] slightly increases with raising the applied power ([Formula: see text] is below 30%), whereas, an abruptly upward jump of nearly two to four times for [Formula: see text] occurs when the discharge transits to H-mode, and then [Formula: see text] monotonously increases with increasing the applied power. In addition, as the pressure rises, [Formula: see text] increases rapidly first and then slowly in pure Ar discharge. However, [Formula: see text] in Ar/O2 mixture gases discharge shows a non-monotonic behavior. It reveals a tendency of first increase at low pressures and then decreases at high pressures, which is because the resistive component of the plasma varies with the electron density [Formula: see text] and the electron effective collision frequency [Formula: see text]. Furthermore, a non-monotonic behavior of transition power threshold [Formula: see text] with the pressure is found, i.e., with increasing the pressure, [Formula: see text] first decreases and then increases. It may be caused by the threshold electron density, which is constant at low pressures [Formula: see text] but increases at high pressures [Formula: see text].