Continuous ultraviolet emissions produced by electron impact on SF6 and NF3

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Abstract
We studied the continuous emissions in the wavelength range 2000 to 3400 Å produced by low energy electron impact on SF6 and NF3. In both cases two different features contribute to the emission spectrum. In NF3, we found a structured emission with maxima at 2880, 3005, and 3130 Å and an onset energy of 8.5±2 eV superimposed on a continuous feature from 2500 to 3500 Å with an onset at about 30 eV. We attribute the structured emission, which has an emission cross section of 2.2×10−19 cm2 at 25 eV, to the NF2 fragment. In SF6, we observed a broad emission feature from 2000 to 3300 Å with maximum intensity at 3010 and 3145 Å with a comparatively weak shoulder at 3160 Å. The 3160 Å feature, which has an emission cross section of about 2×10−20 cm2 at 25 eV, has a single onset at 13.5±1.5 eV, whereas at least two different processes with onsets at 28±2 eV and 42±3 eV, respectively, contribute to the main SF6 emission. The potential relevance of these continuous emissions for diagnostic purposes of NF3 and SF6 processing plasmas utilizing plasma‐induced emission spectroscopy and laser‐induced fluorescence techniques is discussed.