Dissociation fraction in low-pressure inductively coupled N2–Ar and O2–Ar plasmas

Experiments with a Langmuir probe and optical emission spectroscopy (OES) combined with actinometry were performed in inductively coupled rf 13.56 MHz N2–Ar and O2–Ar discharges under the pressure range of 1–30 mTorr and the power range of 400–600 W. The Ar contents in the gas mixture were varied from 5% to 80%. The effect of the Ar content on the variation of the emission line intensities from various species was investigated. The dissociation fraction of nitrogen and oxygen molecules was obtained from the measured intensity peaks of light emission by using the OES actinometry. The dissociation fraction of N2 molecules has a peak value at a specific pressure (11 mTorr). The electron density and the electron temperature were obtained by using a Langmuir probe to investigate the effects of the plasma parameters on the dissociation fraction. The electron density was observed to increase with the power while the electron temperature to decrease with the pressure and power.