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Your search keyword '"Steers, Edward B. M."' showing total 31 results
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31 results on '"Steers, Edward B. M."'

25. The role of oxygen in analytical glow discharges: GD-OES and GD-ToF-MS studies.

Author

Mushtaq, Sohail, Pickering, Juliet C., Steers, Edward B. M., Horvath, Peter, Whitby, James A., and Michler, Johann

Subjects
OXYGEN, GLOW discharges, IRON, COPPER, TITANIUM, TIME-of-flight mass spectrometry, ULTRAVIOLET-visible spectroscopy, FOURIER transform infrared spectroscopy
Abstract

The influence of up to 0.8% volume fraction of oxygen on the argon plasma in a direct current analytical glow discharge was studied for iron, titanium, copper and gold samples using both time-of-flight mass spectrometry and high resolution optical UV-Vis Fourier transform spectrometry. A sudden decrease in sputtering rates, optical emission intensities and ion signals is observed at a current and material dependent threshold fraction of oxygen, and is attributed in part to the formation of an oxide layer on the surface. Beyond the threshold oxygen fraction, a further large continuing decrease in ion signals is observed as the oxygen fraction is increased. This smooth decrease of the observed ion signals is attributed to quenching of ions and argon metastable atoms by oxygen in the flowing afterglow in the flow tube used to promote ion transport to the mass spectrometer sampling orifice. At the threshold oxygen fraction, signals from the mass spectrometer decrease by orders of magnitude more than the optical emission observed from analyte and gas ions. This disproportionate decrease is also likely to be due to reactions in the flow tube. The negative mass spectra were also measured for iron, titanium and copper samples and a significant increase in ion signals is observed at material dependent critical oxygen concentration. Results of studies using calamine (a sample with oxide layer) in pure argon are reported and compared with argon/oxygen mixtures. [ABSTRACT FROM AUTHOR]

Published
2011
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29. Round Robin exercise: Coated materials for glow discharge spectroscopy

Author

Hodoroaba, Vasile-Dan, Hoffmann, Volker, Steers, Edward B. M., Griepentrog, Michael, Dück, Alexander, and Beck, Uwe

Abstract

A Round Robin (RR) exercise on selected coated materials has been carried out with the aim of finding the optimal conditions for the analysis of nitride layers with GD-OES. Such pre-normative work is necessary for the evaluation of parallel development of the production of nitride layers as certified reference materials (CRMs). Two types of samples, Ti–N layer and V–N layer, respectively, with chemical compositions close to stoichiometry and a thickness of ∼3 μm, deposited on a steel substrate, have been provided to the RR participants. Additionally, another type of sample, a (100 nm CrNi/100 nm Cu) multilayer (ML) stack deposited on silicon wafer has also been included in the RR. This sample can be used as a CRM for checking GD spectrometer conditions and it has been proved helpful in further development of GDS instrumentation and methodology. The RR exercise has been performed in the frame of the EC Thematic Network on Glow Discharge Spectroscopy for Spectrochemical Analysis (‘GDS-Net’).

Published
2005
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30. Influence of hydrogen on the analytical figures of merit of glow discharge optical emission spectroscopy—friend or foe?

Author

Hodoroaba, Vasile-Dan, Steers, Edward B. M., Hoffmann, Volker, Unger, Wolfgang E. S., Paatsch, Wolfgang, and Wetzig, Klaus

Abstract

It is well known that the presence of small quantities of hydrogen in an argon glow discharge (GD) causes serious alterations to the excitation and ionisation mechanisms in the GD plasma and hence to the analytical signals. This so-called “hydrogen effect” leads also to a change in the shape of the sputtering crater and its roughness. The present work shows how the manifold effects of hydrogen can be exploited in glow discharge optical emission spectroscopy (GD-OES) in order to improve analytical figures of merit such as analytical sensitivity, detection limits and depth resolution. Other problems caused by the presence of hydrogen, e.g. the occurrence of hydride bands, are demonstrated and discussed. It is shown that start-up phenomena leading to a falsification of the initial part of GD-OES depth profiles can be partially inhibited by controlling the GD source cleanness, and possibly by adding hydrogen.

Published
2003

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