SPATIOTEMPORAL PROFILES OF OPTICAL-EMISSION SPECTRA IN CF4 DISCHARGES AT 1-MHZ

Spatiotemporally resolved observation of optical emission spectra was made in 1 MHz discharges in CF4 and in CF4/N-2 mixture at the pressure of 0.5 Torr. The emission intensity peaks around phases omega t=0 and pi of the applied voltage (V sin omega t) were observed in addition to those around phases omega t=pi/2 and 3 pi/2. These results are similar to those in electronegative SF6/N-2 mixture discharges, while their electrical properties are rather similar to those in electropositive N-2 discharges. Those characteristic optical emissions indicate the existence of a relatively intense field due to the space charge which is yielded by the presence of negative ions in the discharge space.