Signal intensities of positive ions were measured in situ by direct sampling from parallel-plate discharges in CF4/Ar and CF4/O2 mixtures using a quadrupole mass spectrometer. Major positive ions in CF4/Ar discharge are CF x + (x=3, 2, 1) and Ar+. Some of the production of CF2 + and CF+ is considered to be due to the contribution of Ar+. Major positive ions in CF4/O2 discharge are CF3 +, O y + and F y + (y=2, 1). The signal intensity of CO2 + is of the same order as that of F y +. The signal intensities of F y + and O+ in CF4/O2 discharge are higher than those in pure CF4 and O2 discharges, respectively. Intensity ratios of the ions vary with the gas mixing ratios.

Two modes of ionisation waves were observed in the pressure range 0.5-1 Torr and current range 0.1-0.3 mA. With Mode I waves the frequency changed from 20 to 80 kHz with the discharge current. The wave showed a B- type property with both phase and group velocities above 106 cm s-1. The other mode (Mode II) was a kHz wave with a group velocity less than 2*103 cm s-1, which changed from the forward wave to the backward wave with the discharge current. The forward wave showed an exponential increase of both phase velocity and wavelength. Numerical analysis taking into account four species of charged particles agrees qualitatively with the experimental results, and suggests that Mode I was induced by positive ions and Mode II by heavy negative ions.

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Positive ions were measured in situ by direct sampling from CF4 discharge space at 13.56 MHz using a quadrupole mass spectrometer. CF3 + is observed predominantly with smaller amounts of CF2 + and CF+. With increasing RF power, both CF2 + and CF+ shift to the lower energy side of CF3 +, and their intensities tend to increase. Such a phenomenon is also observed as controlling the potential of a sampling tip externally. These seem to suggest that CF2 + and CF+ are produced mainly in the sheath region.