International Symposium on GDOES for Surface Analysis, Keio University, Yokohama, Japan, November 19–21, 2002

During November 19th–21st “the first and last” “International Symposium on GDOES for Surface Analysis” took place in Keio University, Yokohama, Japan. It was organised by Professor Kenichi Shimizu, a famous scientist well known for his electrochemical production of thin and ultra-thin layers and their characterisation by various analytical tools. Professor Shimizu felt that there was a lack of awareness and on the application of glow discharges for the analysis of thin layers, in a research area where glow discharges have to compete with well established methods such as Rutherford backscattering (RBS), secondary ion mass spectrometry (SIMS), proton induced X-ray emission (PIXE), Auger spectroscopy (AES), electron spectroscopy for chemical analysis (ESCA) and total reflection X-ray fluorescence (TXRF). Therefore Professor Shimizu invited around fifteen scientists from all over the world, all well known experts from different analytical methods or application areas, to present an invited lecture and to stimulate and participate in discussions on novel applications of conducting as well as of non-conducting materials. The latter materials are believed to pose a significant challenge for analytical instrumentation even today. In addition to the invited lectures, a poster session was organised covering different aspects of the technique. As a result, poster prizes were awarded to the best five presenters. The whole conference took place at Keio University, in a very friendly atmosphere, which was a prerequisite for all fruitful discussions. The surroundings of the conference site were dominated by the majestic shadow of the Mount Fuji on the horizon, making every problem seem even smaller.

After a warm welcome from Professor Ichiro Inazaki, the Dean of the faculty, and Dr. Masao Horima, Honorary President of the Symposium, Siegfried Hofmann from the MPI of Metal Research based in Stuttgart, Germany, gave an excellent summary of the definitions as well as the analytical figures of merit of surface analytical methods, and this was a good point of reference for the whole conference as it gave all participants the same language for discussions and inter-comparisons. Additionally, he described the state of the art of Auger spectroscopy and highlighted the needs for future applications.

Plate1 L–R: P. Chapon (Jobin Yvon Horiba, France), Miss Le Costumer, P. Le Costumer (Bordeaux University, France), G. E. Thompson (UMIST, UK), N. Jakubowski (ISAS, Germany), R. K. Marcus (Clemson University, USA), V. Hoffmann (IFW, Germany), R. Payling (University of Newcastle, Australia).

M.G. Dowsett, Department of Physics, University of Warwick, UK, demonstrated (using selected applications) the advantages of ultra-low energy SIMS to overcome beam-induced atomic mixing in the upper layers, thus improving the depth resolution significantly.

Richard Payling from the University of Newcastle, Australia, a well known as a consultant for Jobin Yvon Horiba company, gave an overview about recent advances in theory and techniques in rf-GDOES and presented his latest specialism, the calculation of emission lines and line intensities in GDOES, available in recent book as well as on CD-ROM.

Renate Gijbels (co-author Annemie Bogaerts; see their article in JAAS¹), University of Antwerp, Belgium, discussed recent results of theoretical calculations of technical and analytical glow discharges, among which are rf-discharges as well as those in which flowing gases dominate the transport of ions by diffusion to the walls. Densities of different species, their velocities, temperatures, emission yields and many more of the various forms of glow discharges were presented, giving the audience a good understanding of the dominant physical processes taking place.

Phillipe Belenguer, Centre de Physiques des Plasmas et de leurs Applications, Toulouse, France, presented a new approach for calculation of the physical and electrical rf discharge parameters, for instance the cathode sheath thickness, the impedance of the source and the plasma as well as the voltage current characteristics as a function of time, so that in future rf generators as well as matching units can be more easily developed to be fit for purpose.

Kazuaki Wagatsuma, IMR, Tohoku University Japan, demonstrated in various applications the capabilities of modulated discharge voltages in dc and rf-sources and their phase-locked amplification in optical emission spectroscopy. Using this approach he had successfully improved the signal to noise ratio measured by more than one order of magnitude.

Philippe Le Costumer, Department of Applied Geosciences, Bordeaux University, France, used various analytical tools, including GDOES, to characterise analytically the properties of glasses, especially at the surface or the interface or inter-phases between coated surface layers and the bulk material. Although low powers of rf-GDOES were used, thermal effects could not be neglected, so that for such application the techniques still needs to be improved, for instance by power modulation.

Volker Hoffmann, Leibniz Institute for Solid States and Material Research, Dresden, Germany, showed that the reflectivity of a sample surface can increase the emission intensity of the line measured, causing problems for calibration (see his article in JAAS²). Additionally he showed an example of how in multi-layers consisting of non-conducting/conducting interfaces selective sputtering can complicate interpretation of the element distribution in layers by charging of non-conducting islands on a metallic substrate, thus de-focusing the bombarding ions from the glow.

Kenichi Shimizu, Keio Univerity, Yokohama, Japan, the organiser of this meeting, presented his recent results of anodic oxidised Al and Ta. In his lecture he highlighted the point that with rf-GDOES he has a tool which is less expensive than more sophisticated surface analytical techniques but can give valuable information even at a layer thickness of less than 10 nm.

Nerea Bordel described some of the work recently being conducted in Alfredo Sanz Medel’s group at Oviedo University in Spain. They had investigated a commercial rf-GD-AES as well as a home-built DC-GD-TOF-MS and therefore could give a comparison of both techniques. In particular, their modular approach to a new glow discharge (see their article in JAAS³) looks convincing in terms of the application of technical layers shown.

Ken Marcus, Clemson Univerity, Clemson, USA, focussed his presentation on answering the question as to where we are coming from in glow discharge spectroscopy and where we might be going in the future. He convinced the audience that even scientists can learn from history in order to develop the instrumentation needed for the future.

Norbert Jakubowski, Institute for Spectrochemistry and Applied Spectroscopy (ISAS), Dortmund, Germany, described his groups’ experience in home-built instrumentation in glow discharge mass spectrometry. He presented an approach using absolute sensitivity factors (useful yields) to convert the intensity/time profiles measured in the analysis of thin Ni/Cr layers to concentration/depth profiles wanted. He presented the first results of an rf-driven Grimm-type ion source operated at high powers (80 W) with high gas flow rates up to 300 ml min⁻¹, which they had coupled to an ICP-SFMS (Axiom, ThermoElemental, Winsford, UK). They have achieved 2 orders of magnitude improvement in comparison to their low flow rate GD source coupled to a quadrupole mass analyser.

Plate2 L–R: Professor G. E. Thompson, two Geishas, Dr. Horiba, Professor Kenichi Shimizu.

Michael R. Winchester, National Institute of Standards and Technology, Gaithersburg, USA, gave a comprehensive overview of the standards and standard reference materials for GDOES. The outcome of his lecture was that although a couple of standards and certified standard reference materials with conducting layers are commercially available for GDMS there is still a lack of reference materials for non-conducting single and mutli-layer samples of advanced materials.

Kim Marshall, Leco Corperation, St. Joseph, USA, discussed the advances of GDOES in comparison to well established techniques for surface analysis (Auger spectroscopy, ESCA, SIMS). He showed the market niches and special applications where GDOES can compete well or even is superior in comparison with the above-mentioned techniques.

Finally, Patrick Chapon, Jobin Yvon Horiba, Paris, France, presented a broad overview of novel applications from industry. Most impressive was the new sample holder for automatic sample changing and cleaning of the source. He pointed out that even for bulk analysis GDOES can be used, giving a reproducibility of better than 3%.

References

1. A. Bogaerts, A. Okhrimovskyy and R. Gijbels, J. Anal. At. Spectrom., 2002, 17(9), 1076–1082.
2. R. Dorka, R. Kunze and V. Hoffmann, J. Anal. At. Spectrom., 2000, 15(7), 873–876.
3. J. Pisonero-Castro, J. M. Costa-Fernández, R. Pereiro, N. Bordel and A. Sanz-Medel, J. Anal. At. Spectrom., 2002, 17(8), 786–789.

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