Optical emission spectroscopy used to study the characteristics of the capacitive radio-frequency discharge in argon

Abstract

Capacitively coupled radio-frequency (13.56 MHz) glow discharge in argon at low pressure (200 mTorr) has been studied by optical emission spectroscopy (OES) and electrical probe. Increasing power density resulted in lowering of the electron temperature Te and increase of the electron density ne. The α to γ transition in this case takes place smoothly. The intensity (I750.4) of the emission line at 750.4 nm due to 2p1→1s2 transition closely follows the variation of ne with power density. Calculation of the electron-energy probability function shows that electron occupation mainly changes in the high-energy tail, which explains close resemblance of I750.4 to ne. At moderate pressures, only OES method was applied to observe α-γ transition which is abrupt in this pressure range.