engleski

Characterization of RF nitrogen plasma by optical emission spectroscopy

Optical emission spectroscopy was applied to study the characteristics of low pressure nitrogen plasma suitable for discharge cleaning of electronic components. Plasma was created in a glass tube with an inductively coupled RF generator with the frequency of 13.56MHz and the output power of 120W. Vacuum system was pumped with a roots and a two stage oil rotational pump. Commercially available nitrogen was leaked into the discharge vessel through a precise leak valve. The pressure during experiments was between 10 and 100 Pa. The electron density and temperature were measured with a double Langmuir probe and were about 1x1016 m-3 and 5eV, respectively. The optical emission spectra were measured with a S2000- Ocean Optics spectrometer. A rich spectrum of nitrogen molecules was observed between 350 and 800nm. The predominant lines were bands corresponding to neutral nitrogen molecular transitions from B3Π g to A3Σ +u states. The bands in this system were most intense in the red part of the spectrum indicating transition to different vibrationally excited states. Transitions between the neutral nitrogen molecule C3Π u excited state to B3Π g excited state were detected in the violet part of the spectrum. These transitions were less intensive indicating a rather poor population of the highly excited C3Π u states. Ionic transition states were also observed. The transitions between the B2Σ +u to X2 Σ +g positively charged molecular ionic states were detected in violet range of the spectra. The results were explained with N2 potential curves.

nitrogen discharge; optical emission spectroscopy

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