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Weinstein, Viktoria (2011) Factors affecting glow discharge plasma spectroscopy: effect of the molecular gases and sample geometry on the spectra. Doctoral thesis, London Metropolitan University.
This thesis is a part of a major investigation on fundamental processes in the glow discharge plasma. ln this work the effect of molecular gases, originating from sample and source contamination, has been examined. An extensive study on the emission spectra of copper with a high resolution Fourier transform spectrometer using argon and neon as carrier gases was performed. Small amounts of hydrogen were introduced into the GD source in order to verify the effect on the intensities of the emission lines. Supporting information on the spectra was gathered with a commercial GD-OES instrument. The effect of all three molecular gases (H2, O2, and N2) was studied with a fast flow GD-MS on three sample materials (Cu, Ti, and Fe). Sputter rates and also the crater surfaces after sputtering were considered. A small, experimental part of this project concentrated on testing the advantages of using hollow or shallow cathodes instead of flat samples, recording wide emission spectra with the FTS.
Conclusions were made about plasma mechanisms by observing the intensity changes of the emission lines and ion signals. It was found that the reactions occurring in the plasma are depending on the carrier gas and differ for argon and neon; also each investigated molecular gas has shown an individual effect. This supports previous investigations by other researchers. The major differences between the used GD-OES and GD-MS systems for this kind of study were highlighted.
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