Experimental and numerical investigations on time-resolved characteristics of pulsed inductively coupled O2/Ar plasmas

Abstract

The time-resolved characteristics of pulsed inductively coupled O2/Ar plasmas have been investigated in this paper, by means of a Langmuir probe and a global model. The plasma properties, e.g., the electron density, effective electron temperature, and electron energy probability function (EEPF), have been experimentally investigated under various discharge conditions, combined with the comparison with simulated results. It is found that when the power is switched on, the electron density increases rapidly and then it reaches to a steady state with a constant value. When the power is switched off, the electron density exhibits a peak at the initial afterglow period, and then it decays gradually to a very low value. This peak may be caused by the detachment of negative ions. Moreover, it is noted that the effective electron temperature also increases to a peak value at the early afterglow, which can be understood by examining the evolution of EEPFs with time. Indeed, when the power is switched off, more moderate-energy electrons are produced through the collisions among the excited state particles and the energy loss of energetic electrons, and this is responsible for the peak of the effective electron temperature at the initial afterglow. In addition, the simulated results show a qualitative agreement with the experimental data, with the exception of the peaks in the electron density and effective electron temperature in the afterglow. The discrepancy in absolute values may be caused by the assumption of a Maxwellian electron energy distribution function distribution in the model.