Glow and glory

Over the years JAAS has developed to become one of the most important journals in atomic spectroscopy, where authors publish their actual research work and find appropriate attention in all areas of plasma based atomic spectroscopy and, in particular, in analytical glow discharge spectroscopy. Glow discharges are still an important focus and feature of JAAS. The glow discharge community is a small one compared with that of the ICP, but nevertheless it is very active and productive in terms of both applied and fundamental research and this is the reason why JAAS has always been involved with it. For instance, over the years we have seen special issues of JAAS being attributed to tuneable sources¹ and glow discharges.² Also, as an experiment to demonstrate the fastest way of publication, an electronic adjunct section of JAAS became available on the internet at the end of the last millennium: the “glow discharge section of JAAS”. This was done to support hot topic research in new and developing areas. The adjunct journal was intended to become an important publication tool for the European Thematic Network on Analytical Glow Discharges, to improve the speed and the flow of scientific information and to make analytical results available worldwide to the analytical community without delay, with the idea of combining the scientific efforts in this field and stimulating and improving discussion about unsolved problems. In the end this initiative was so successful that nowadays every article of JAAS is available online as an advance article and also the time lag between submission and internet publication has significantly shortened (just as a reminder, an article in JAAS is published in less than 90 days), which is fast compared with all other journals in plasma source spectroscopy.

Two EU projects were supported and accompanied, the EU Thematic Network, which has already been mentioned, and an instrumental research project, “Automated GDMS”, from which many ideas have been used for the development of a new instrument in the field.³

Now JAAS will take an interest in two new EU projects. One, EMDPA, had already been funded at the end of last year. The other one, GLADNET, had its “kick off meeting” just before the 2007 European Winter Conference on Plasma Spectrochemistry. More detailed information about the ideas of both projects will follow at the end of this editorial. And is it not glorious if more than 30 partners from more than 20 European countries, with a total of more than 100 scientists, are starting joint and coordinated efforts to find new ways to investigate the big unknowns in the glows which can lead to the next generation of glow discharges with much enhanced analytical capabilities?

It is the purpose of this Editorial to keep the reader informed about such large scale projects in plasma based spectroscopy and it serves as an appetizer for papers coming soon. It is also the aim of this Editorial, in conjunction with a Perspective article, to make the hot topics in glow discharge spectroscopy (GDS) in the above mentioned two EU projects more transparent and maybe this will also help to coordinate international activities. Both the Editorial and the Perspective are more a personal view and compendium of actual research topics rather than a comprehensive review of research topics which are related to both EU projects. Some very comprehensive reviews have recently been published.^4,5

GLADNET

The new Analytical Glow Discharge Marie Curie Research Training Network (RTN) “GLADNET” is the result of many efforts to obtain significant EC funding for research on analytical glow discharges. The earlier (1999–2002) Thematic Network on Analytical Glow Discharge Spectroscopy (GDS) under the FP4 Standards, Measuring and Testing (SMT) programme had led to increased—and continuing—collaboration between those involved in the various aspects of GDS, those using OES and those using MS, those involved in modelling and those working experimentally and, most importantly, between those involved in fundamental studies and those undertaking materials analysis. The importance of this last factor was demonstrated at many meetings when it was found that apparently anomalous analytical results were linked to particular excitation processes in the discharge and when effects predicted by fundamental studies were identified as occurring in analytical work.

However, the Thematic Network did not provide funding or personnel for research work. Early in the FP6 programme, proposals for an RTN in this area were submitted by the University of Oviedo and London Metropolitan University, but both were unsuccessful. The EC later introduced a 2-stage application process, and at a meeting of the informal European Working Group on Glow Discharge Spectrometry (EW-GDS), after the Winter Conference on Plasma Spectrochemistry in Budapest (February 2005), it was agreed that a further joint attempt should be made to establish an RTN related to analytical GDS. Edward Steers did not feel able to lead the coordination, and Johann Michler from the Swiss Federal Laboratories for Materials Testing and Research (EMPA), Thun, was persuaded that EMPA should be the coordinator, although Edward Steers remained heavily involved in the drafting of the proposals.

Although the 2-stage process meant that less documentation was required at Stage 1, we soon learnt that the majority of the planning work was still required at this stage! However, the Stage 1 proposal was accepted: we were invited to submit Stage 2, which again satisfied the referees, and eventually the contract was signed in December 2006, and came into force on February 1st 2007. The “kick-off” meeting was held immediately preceding the Winter Conference on Plasma Spectrochemistry in Taormina (February 2007), the culmination of a two year preparation period.

GLADNET (see Fig. 1 for the logo) involves 16 partners and fulfils all three aspects of the EC Marie Curie RTN programme: it is international, interdisciplinary, and inter-sectorial; partners are in twelve countries, chemistry and physics university departments are involved and some of the research institutes work on material sciences. Four of the partners are research institutes, seven are universities and five are from industry, including one SME (for more details see Table 1). The geographical distribution of the partners is shown in Fig. 2. Two of the partners are in newly joined EU states and three of the University partners are in “Third Countries”, i.e. not in the EU or Associated states. The proportion of partners from Research Institutes and industrial firms in GLADNET is higher than in many RTN, particularly in the science area, and is the direct result of the experience gained in the Thematic Network. During the drafting of the proposals it became clear that more groups wished to participate than could be accommodated in the Network, and there is therefore an outer circle of “affiliates”, at present numbering about 20, who are closely interested in the Network project and will be represented at many Network meetings. GLADNET will fund ten Early Stage Researcher (ESR) positions, all of three years duration, and five Experienced Researcher (ER) positions of varying durations. ESRs will normally be registered as PhD students, whilst ERs must have had at least four years (and not more than ten years) postgraduate research experience or hold a PhD degree.

Fig. 1 GLADNET logo.

Fig. 2 Geographical distribution of partners.

Table 1 GLADNET partners

Partner number	Organisation name and department	Acronym	Country
Research institutes
1	Swiss Federal Laboratories for Materials Testing and Research, Thun (Coordinator)	EMPA	Switzerland
2	Leibniz Institute for Solid State and Materials Research Dresden	IFW	Germany
3	Research Institute for Solid State Physics and Optics, Budapest	RISSP	Hungary
4	Corrosion and Metals Research Institute, Stockholm	KIMAB	Sweden
Higher education
5	Imperial College, London, Physics Dept.	ICSTM	UK
6	London Metropolitan University, DCCTM	ULMET	UK
7	University of Antwerp, Chemistry Dept.	UA	Belgium
8	University of Oviedo, Chemistry Dept.	UNIOVI	Spain
9	St. Petersburg State University, Chemistry Dept.	CRI-SPSU	Russia
10	University of Belgrade, Faculty of Physics	FoPB	Serbia
11	Indiana University, Chemistry Dept.	IU	USA
Industrial firms
12	AQura GmbH (Degussa AG), Hanau	DEG	Germany
13	LECO Instrumente Plzen, spol. s r.o.	LECO	Czech Republic
14	Thyssen Krupp Steel AG, Dortmund	TKS	Germany
15	Shiva Technologies Europe, Toulouse	STE	France
16	TOFWERK AG, Thun	TOFWERK	Switzerland

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Research on GD spectrometry in Europe is currently fragmented; most of the research teams are small or have only a small part working in this field. The teams tend to be specialised, using either OES or MS—this may be appropriate for particular analytical tasks, but it restricts the flow of information on the glow discharge itself. Furthermore, teams are working on particular aspects in groups in Physics, Chemistry or Materials Science Departments, concentrating on the discharge physics and spectroscopy, the analytical chemistry or the characterisation of materials. Moreover, teams in research institutes and particularly in universities tend to have limited awareness of practical analytical problems. Thus, at present a PhD student may acquire a good knowledge, say, of experimental atomic spectroscopy and discharge processes, but has no idea of the practical analytical applications of this knowledge.

GLADNET aims to rectify this deficiency in three main ways. (1) A training manager has been appointed, with overall responsibility for all aspects of the researcher training. (2) All the researchers appointed will spend some of their time in the laboratories of other partners, including a period in an industrial analytical laboratory. (3) Network-wide training courses will be held every six months; these will combine specific training courses for the appointed researchers (and for other research staff in training) with scientific presentations on the various Network projects. Where possible, these meetings will be linked to conferences relevant to some aspect of GDS. Thus, the September 2007 training meeting will be linked to ECASIA (European Conference on the Applications of Surface and Interface Analysis) in Brussels, whilst it is intended that the meeting in September 2009 will be linked with the Colloquium Spectroscopicum Internationale (CSI) in Budapest. Moreover, the researchers will be encouraged to consider their future career prospects throughout their training. Thus GLADNET should produce a fresh generation of research personnel with a wide understanding of analytical glow discharge techniques and accustomed to working in a pan-European context.

The overall scientific objectives of the Network are to link the leading European laboratories working in this field, to overcome the fragmentation of research and to further develop GD spectroscopy as a leading tool for the analysis of solids, layers and interfaces. Improved analytical techniques will, in turn, improve development of materials and production, and hence the competitiveness of European industry. The research work of the Network is divided into five “work packages”, each coordinated by an expert in that field, as follows.

WP1. Pulsed discharge studies

There are two strands to this work package. In the first, fundamental research concerning the application of pulsed rf discharges in GD-OES and -MS is planned, including the application of a source, newly developed at IFW, with integrated voltage and current probes to give time resolved voltage and current signals. The influence of the light elements such as H₂ and N₂ on the electrical discharge parameters will also be studied. In combination with accurate sputtering rate measurements, as well as temporal and spatial resolved light intensity measurements, the development of improved models for the quantification of rf-GD-OES in continuous and pulsed mode is intended. In the second strand, the properties of pulsed hollow cathode discharges will be studied using time of flight (TOF) GD-MS, and results will be compared with modelling data. These studies will include the effect of molecular gases (H₂, N₂, etc.) on the ionic spectra of the sample.

WP2. Experimental studies on glow discharge processes

The effects of molecular gases on observed GD spectra will be examined and interpreted in terms of the individual excitation processes, including comparison with modelling predictions. Where appropriate, high resolution Fourier transform spectroscopy will be used for unambiguous line identification and study of line profiles (e.g., to assess gas temperatures). Spatially resolved spectra will be recorded to link spectral effects to specific regions of the discharge and hence assist in the interpretation of the processes involved.

WP3. Modelling studies

These include (i) modelling of the effect of molecular gases on the electrical parameters, emitted spectra and ion concentrations including a collision–radiative model for Ar + H₂, Ar + O₂ and/or Ar + N₂ discharges coupled to experimental verification, and (ii) modelling of crater shapes of pulsed discharges including a physical model for the ignition of the plasma and thermal effects of the sputter gas or sample to understand the dependence of the crater shape on gas flow, pressure and electrical parameters.

WP4. Analytical studies

This will cover a wide range of analytical applications: new applications of continuous and pulsed rf glow discharges for the analysis of advanced materials (nano-structured materials, polymers and other thermally unstable materials); investigation of the analytical potential of the newly developed double focusing GD-MS instrumentation; exploration of GD-TOFMS for the analysis of macromolecular materials, in particular of the effect of hard and soft ionisation processes on long molecular chains in the pulsed GD plasma; assessment of laser-assisted GD sputtering for spectrochemical imaging; quantification of H in steels.

WP5. Complementary studies

These are aimed at producing the fundamental data necessary for modelling calculations. Currently, reaction rate coefficients are available for, for example, asymmetric charge transfer excitation for elements (particularly volatile elements) commonly used in lasers, but not for less volatile elements of major analytical importance. Another current requirement is for a searchable database containing reliable experimental data on glow discharge spectra of analytically important elements.This ambitious programme is the largest ever European collaborative research programme on glow discharge spectroscopy and, even if somewhat daunting, is an exciting challenge to all involved. This network opens new capabilities of enhancing GD research, not only in the EU but hopefully worldwide. It can help to coordinate the research work needed to build better sources for quite new analytical and technical applications and bring people together from various fields for a new joint effort.

To achieve this ambitious programme it is essential that we are able to fill the ESR and ER positions provided under this RTN as soon as possible: the salaries are generous, including a career exploratory allowance. Normal Marie-Curie mobility rules apply—in general, applicants should not be nationals of the country where the position is offered, nor have worked in that country for more than 12 months in the past 3 years. For details of the application procedure, and for further details of the project and the network partners, visit our website: www.gladnet.eu.

Following the formal “kick-off” meeting in February, the first major scientific meeting of the Network will be in September 2007. It had already been suggested that the next meeting of the informal European Working Group on Glow Discharge Spectrometry (EW-GDS) could be linked to the European Conference on the Applications of Surface and Interface Analysis (ECASIA) in Brussels. This EW-GDS meeting will now be joined to the GLADNET meeting. There will be a training course in Antwerp on 9–12th September for the newly appointed GLADNET researchers and other students from the GLADNET consortium; on Thursday 13th September, there will be a GDS session at ECASIA in Brussels (see www.ECASIA07.be) and on Friday 14th September there will be an open EW-GDS/GLADNET/German GDS Users Group meeting at the Vrije Universiteit Brussel (VUB) (see www.GLADNET.eu), at which more details of the various GLADNET work packages and projects will be given.

EMDPA

EMDPA is the acronym for “New Elemental and Molecular Depth Profiling Analysis of Advanced Materials by Modulated Radio Frequency Glow Discharge Time of Flight Mass Spectrometry”. EMDPA is a STREP project funded by the EU (contract STRP 032202) in the 6th framework program under the Thematic Priority No. 3—Nanotechnologies and nano-sciences, knowledge-based multifunctional materials and new production processes and devices. EMDPA started September 1st, 2006.

The mission statement of the project is stated as follows: “EMDPA will provide research laboratories and industry with a unique “multi-dimensional” analysis tool of all types of layered materials, allowing direct, simultaneous elemental and molecular quantitative measurements with a sensitivity down to 100 ppb in the depth profiling mode for all elements of the Periodic Table, in observed zones of millimetre dimensions, through the development of a Micro Modulated or Pulsed Radio Frequency Glow Discharge Time of Flight Mass Spectrometer”.

EMDPA gathers 10 multidisciplinary organisations from 7 countries, carefully selected for the complementary expertise they bring to the project: for more details see Table 2 and Fig. 3.

Fig. 3 Geographical distribution of the partners.

Table 2 List of partners, locations and acronyms

Partner and location	Acronym
HORIBA Jobin–Yvon (coordinator), Longjumeau, France	HJY
University of Manchester, UK	UoM
National Institute of Lasers, Plasma and Radiation Physics, Bucharest, Romania	NILPRP
Gesellschaft zur Foerderung der Analytischen Wissenschaften e.V., Dortmund, Germany	ISAS
Swiss Federal Institute for Materials Science and Technology, Thun, Switzerland	EMPA
Centre de Physique des Plasmas de Toulouse (now Laplace laboratory), Toulouse, France	CPAT
TOFWERK AG, Thun Switzerland	TW
University of Oviedo, Spain	UNIOVI
Università degli Studi di Catania, Italy	UNICT
ALMA Consulting Group, Lyon, France	ALMA

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Some members of EMDPA were already partners in the EC Thematic Network on Glow Discharge and have experience of work in common, and many are also involved or associated with the EU Gladnet network indicating the mutual benefits that the cooperation between the two projects may bring.

The partnership embraces experts in plasma physics/chemistry and plasma-surface interactions (CPAT, NILPRP and UNICT), renowned groups in GD-MS design, chemometrics and data handling (ISAS, UNIOVI and EMPA), a recognised research centre with expertise in all aspects of material sciences (UoM), a provider of innovative TOFMS technologies (TW), and a large company manufacturing GD optical spectrometry instruments (HJY).

The EMDPA web site is accessible through both www.emdpa.eu or www.emdpa.com addresses and provides information on the work in progress and on the activity of the partners.

A logo has been created, giving identity to EMDPA, as is shown in Fig. 4. It summarises the various aspects of the project, the multi-layered sample, the GD plasma with its various constituents, the parabolic ion trajectory in the time of flight mass spectrometer and the MS spectrum.

Fig. 4 EMDPA logo.

State of the art and objectives of the research

Surface and depth profiling chemical analysis of multi-layer materials demand a “multi-dimensional” knowledge, including elemental and molecular information and require direct sampling of the solid to provide the fundamental and strategic information for new materials development directed by a precise mechanistic understanding.

Surprisingly, if GD-OES is now clearly focused towards depth profile analysis but fails to provide molecular information, GD-MS essentially remains a bulk elemental technique, though one could think that it embraces the speed of GD-OES with MS detection capability.

Pulsed sources are now available in some GD-OES instruments but they have been extensively used in plasma deposition systems for electronics and a rich literature describes many of the benefits that they offer through their temporal distribution of power, providing a real possibility of separating elemental and molecular excitations.

The simultaneous recording of elemental and molecular information in the same sequence has been investigated for the first time in the analytical community by Lewis et al. through the coupling of ultra-fast MS instrumentation to a pulsed source.⁶

To date, however, little progress has been made towards instrumental development, mainly because of the absence of complete understanding of some key phenomena:

sputtering mechanisms and ionisation processes;

molecular chemistry in plasmas;

ion transport phenomena.

We thus defined the following research objectives for the project.

Objective 1

The first objective is to understand and model the sputtering mechanisms and the ionisation processes involved in the GD source. A better understanding of the relation between power coupling efficiency and the nature of the material, as well as a better control of ion energy with the discharge parameters, will lead to new micro-modulated and pulsed sources suitable for conductive and insulating materials.

Objective 2

The sputtered surface will be characterised to understand the molecular chemistry of the plasma. The source parameters will then be optimised for simultaneous quantitative elemental and molecular analysis.

Objective 3

The third objective concerns understanding and optimising ion transport and ion detection. Ion blanking as well as electron blanking will be tested for optimum and simultaneous negative and positive ion analysis. An ion mobility interface will be implemented for isobaric separation.

Objective 4

The final objective is to evaluate the performance of the instrument including new developments made in source design, ion optics, and detection, as a result of the work defined in the above objectives. This evaluation will be carried out using well characterised and reproducible samples of advanced materials.

The EMDPA research objectives are shown in Fig. 5.

Fig. 5 Research objectives.

Organisation of the work

The various tasks have been distributed within 7 work packages, as is shown in Fig. 6.

Fig. 6 Work package organisation.

The specificity of EMDPA is that for each concept developed within EMDPA, specific materials will be elaborated, allowing a clear and precise estimation of the achievements and enabling knowledge based instrument development and an expectation that for each targeted market, relevant materials will be evaluated, allowing adequate dissemination of the results.

Work package 1: materials for testing, validating and benchmarking

This work package will first define the reference samples and new materials, as well as the specifications required for their analysis. As a second step, the specimens will be synthesised. Finally, they will be analysed by the GDMS instrument and results will be compared with those from other techniques.

Work package 2: generation of plasma knowledge for rf-GD-TOFMS

This work package aims at acquiring knowledge in (i) plasma physics, (ii) plasma chemistry, (iii) plasma surface interactions and (iv) transport of ions to the interface. Experimental characterisation (electrical and optical) and numerical modelling of the plasma discharge will be used.

Work package 3: ion generation and collection

Results from work package 2 will define new source configurations that need to be tested. The choice on source geometry will be made and the source will be built. This work package also deals with designing a high transmission and easily cleanable ion interface.

Work package 4: ion measurement

This work package includes building and evaluating the high resolution mass spectrometer, adequate time of flight electronics and an ion mobility cell.

Work package 5: test and evaluation

This work package integrates all developments regarding the source, the interface, the mass spectrometer, electronics and software.

Work package 6: dissemination and standardisation

Internal and external dissemination is of particular importance and will be achieved through an internal and some public websites, as well as participation in conferences and various publications. An exploitation plan will also be built and regularly updated.

Work package 7: management

This work package ensures good administrative work and the financial follow-up required by the EC, as well as support for technical reporting and archiving. Coordination and communication between partners are also included in this work package.

20 participants gathered at HJY for the kick-off meeting in September 2006 and 22 were present in February 2007 for the first half year meeting organised at the University of Catania by Professor A. Licciardello. During these first six months multiple cross visits have set the base for a fruitful and solid collaboration between partners.

Thanks to the presence within the consortium of a consulting company in charge of the coordination of administrative matters, it was possible to essentially focus both meetings on the scientific and technical aspects of the project. The first one has clearly identified and defined the samples required to assess the performance, whereas the second meeting was focused on the source and lamp designs.

As a conclusion it can be summarised that the tuneable aspect of analytical GD now brings a lot of interest into the scientific community as it can address a variety of specific needs not easily covered by other instrumentation. EMDPA, with its focus towards surface and depth profile analysis, explores some of these needs. Its challenging goal is to provide new instrumentation that will offer new opportunities to precisely and correctly characterise the emerging materials and understand their behaviour under various conditions, thus promoting breakthroughs at the research and industrial levels.

Final remarks

Finally, it should be mentioned that both funded projects, EMDPA and GLADNET, are still open for discussion and cooperation. Everyone interested in them should directly contact the respective coordinators using the links given in the text. As already mentioned, JAAS will follow both projects over the coming years, and it is already planned now to publish a special issue attributed to glow discharges after the mid-term meeting of both projects, which means in roughly 18 months from now. The authors of this Editorial welcome all authors who will send their novel plasma based research papers to JAAS, so that this journal can become a dynamic platform for novel discharges including glow discharges at reduced and atmospheric pressures and all kinds of miniaturized plasmas with and without microchips.

Finally, it is the idea of the other members of this editorial team to acknowledge the enthusiasm and long term dedication of Professor Edward Steers. Without his power and energy most of the glow discharge research in the European Community would still be fragmented and uncorrelated. He has brought many people from various disciplines together for a joint effort in fundamental and applied research. Many of them started as partners and cooperate now as good friends. Many thanks to Edward.

Norbert Jakubowski

ISAS—Institute for Analytical Sciences, P.O. Box 10 13 52, D-44013 Dortmund, Germany. E-mail: jakubowski@isas.de; Fax: +49 231 1392-120; Tel.: +49 231 1392-108

Edward Steers

London Metropolitan University, 166–220 Holloway Road, London, UK N7 8DB. E-mail: e.steers@londonmet.ac.uk

Agnès Tempez

Horiba Jobin Yvon, 16–18 rue du Canal, F-91160 Longjumeau, France. E-mail: agnes.tempez@jobinyvon.fr

References

1. R. K. Marcus, E. H. Evans and J. A. Caruso, J. Anal. At. Spectrom., 2000, 15, 1.
2. J. Anal. At. Spectrom., 2003, 18, June issue.
3. M. Hamester, L. Rottmann and J. Hinrichs, LaborPraxis, 2006, Jan./Feb., 42.
4. V. Hoffmann, M. Kazik, P. Robinson and C. Venzago, Anal. Bioanal. Chem., 2005, 381, 173.
5. M. R. Winchester and R. Payling, Spectrochim. Acta, Part B, 2004, 59, 607.
6. C. L. Lewis, M. A. Moser, W. Hang, D. E. Dale, C. Hassell and V. Majidi, J. Anal. At. Spectrom., 2003, 18, 629.

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Footnote

† The HTML version of this article has been enhanced with colour images.

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