GROWTH – DEDICATED CALL – 1/00
TOPIC III.30
Quantitative determination of Nitrogen, Carbon and Oxygen for
spectroscopic analysis methods
1. CONFORMITY WITH THE WORK PROGRAMME
This topic falls under the Competitive and Sustainable Growth Programme, generic
activity Measurement and Testing. Specifically, it is related to Objective GROW-20006.3 support to the development of certified reference materials for which expressions of
interest have been called.
2. KEYWORDS
Quantitative analysis, Certified reference materials, GD-OES, SNMS, spectroscopic
analysis, Nitrides, Carbides, Carbonitrides, Oxides, Oxynitrides
3. SUMMARY OF OBJECTIVES AND JUSTIFICATION
The increasing application of hard coatings, decorative coatings and protective coatings
(nitrides, carbides and carbonitrides) as well as passivation layers (oxides an
oxynitrides) require the knowledge of composition and layer thickness during the R &
D period, for production quality, checks as well as for damage analysis. GD-OES and
High Frequency (HF) -plasma SNMS are powerful tools for the analysis of bulk
materials and coatings in the nm to µm thickness range. Both methods can be applied to
electrically conducting and insulating layers and bulk materials. GD-OES and SNMS
intensities measured on these technologically relevant chemical compounds can
generally not be converted into element concentrations without CRM’s. This holds also
for other spectroscopic methods like Glow-Discharge Mass Spectrometry (GD-MS),
Auger Electron Spectroscopy (AES), X-ray Photoelectron Spectroscopy (XPS) and
Secondary Ion Mass Spectroscopy (SIMS). In general, there is a serious lack of
reference materials applicable to the quantitative analysis of nitrogen, carbon and
oxygen in coatings, layers and bulk materials. Consequently, the aim of this proposal is
to evaluate and develop reference materials, which can be used for the quantification of
GD-OES and SNMS measurements and other spectroscopic methods.
4. BACKGROUND
Accurate, reliable, and rapid methods of composition analysis are important in material
research and quality control in production and testing of protective layers, in corrosion
and ageing studies, as well as in damage analysis. It may be necessary to analyse either
the bulk material or, for treated and/or coated materials, the variation of elemental
concentrations from the surface to a depth of 100µm. The GD-OES method is primarily
used for the analysis of bulk metallurgical materials (e.g. steels) and for depth profiling
of thick coatings (e.g. 1- to about 100 µm Zn on steel sheets) [1-3]. Moreover, this
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technique has considerable potential for thinner layer systems (some 10 nm to some 100
nm, e.g. PVD and CVD films or coatings). GD-OES is of special interest for industrial
application because of fast analysis cycles (no sample transfer, pre-vacuum technique,
and short measurement times) and of high elemental sensitivity and low cost compared
to traditional surface analysis (AES, XPS, SIMS). Therefore, both general and
application aspects of GD-OES are under discussion now in ISO/TC201/SC8.
Furthermore, January 1999 a Thematic Network on Glow Discharge Spectroscopy
(GDS) for Spectrochemical Analysis founded by the EC (Contract No. SMT4 - CT98 7517 (DG 12 - HIAS)) has been established. The objective of this network is to assist in
the further development of analytical methods using GD-OES and Glow Discharge
Mass Spectrometry (GD-MS) including their range of applications.
(See web page: http://homepages.unl.ac.uk/rogresi~)
For the conversion of detected emission line intensities into elemental concentrations
and, in the case of layer depth profiling, of sputter time into depth, reference materials
of known composition must be used [4]. Most of the quantification methods applied
today define the sputter rate in terms of mass loss per unit time deduced from integrated
signal intensity [4]. However, the conversion of mass loss into depth requires the
knowledge of the material density. Usually, the weighted average of the densities of the
pure elements, or the weighted average in terms of the concentrations in atom percent, is
utilised. This approach leads to accurate results for most metallic alloys. However,
significant uncertainties in the density estimation may occur for more complex materials
that contain gases or other light elements, like oxides, nitrides, or carbides [5]. Such
inaccurate densities result in systematic errors for the calculated sputter depth.
Further problems can arise from the influence of molecular species, which can be
formed in the vicinity of the sample surface if the sample contains highly reactive
elements like oxygen, nitrogen etc. Background signals and line interferences must be
considered as well, especially in case of trace element detection [5].
For metallurgical applications like steel analysis a large variety of CRM´s are available.
However, in case of nitrides, carbides and carbonitrides only few CRM´s containing
nitrogen and carbon exist. In particular the newly developed High Frequency (HF) mode which allows the analysis of electrically insulating materials like oxides,
oxynitrides and varnishes [6] requires reference materials with different concentrations
of oxygen and nitrogen. For this new GD-OES applications there exist no useful
standards at all.
The activities of working group A in the GDS network are focussed on the field of
standard procedures and standard reference materials. As one result also the
development of reference materials with varying nitrogen, carbon and oxygen contents
in the per cent range is recommended.
In the last decade, HF-plasma SNMS [7,8] has become a well-established method in the
field of elemental depth profiling and bulk analysis. In contrast to the GDS techniques,
the particles sputtered by means of the low-pressure plasma of HF-plasma SNMS are
not considered to take part in plasma processes apart from being partially ionised. This
fundamental difference alleviates quantification; on the other hand, not all the physical
processes influencing the quantification of this comparatively young method have been
clarified yet.
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By using the recently introduced HF sputtering mode (HFM) [9], electrically nonconducting samples like nitrides, carbides and oxides - bulk samples as well as layers
with thickness up to a few µm - can be investigated by means of HF-plasma SNMS. In
contrast to alloys and other metallic samples, quantification in the wide field of
technologically relevant chemical compounds is still hampered by large, and often
matrix dependent, variations of detection factors. This is partly due to secondary ions,
which can contribute to the measured signal in HFM [10]; methods for their suppression
are under development. Other problems eventually arise from matrix dependent
emissions of molecular secondary neutrals, which can deplete the conventionally
measured atomic signal, and from variations in the angular and energy distributions of
the sputtered neutrals [8]. Using CRM’s in the quantification procedure should
compensate such matrix effects.
As for the calibration of sputter depth, matrix-near standards are also needed in HFplasma SNMS. Comparing the sputtered mass of a CRM with the elemental signal
integrated over sputtering time results in absolute elemental detection factors, which,
after an appropriate check for matrix dependence, should be directly applicable to any
commercial sample [8].
Nitrides, carbides and carbonitrides occur in high alloyed steels and other highperformance metals as precipitates on a micrometer or sub-micrometer scale. Material
properties are strongly influenced by the nature of such precipitates. Therefore, their
composition, structure, size and distribution in the metal matrix are systematically
investigated. Currently, analysis of submicron particles is frequently carried out by
means of Transmission Electron Microscopy (TEM); for particle diameters >1µm
Electron Probe Microanalysis (EPMA) or SIMS are used. Modern AES instruments
have the potential to investigate small structures on a nm scale.
As exemplified by [11], quantitative analyses on complex working materials are still
based on pure compounds only (h-BN powder in “In foil and diamond CVD” in [11]),
although the matrix dependence of sensitivity factors are well known. Some of the
quantification problems inherent in these analyses can very probably be reduced by
applying sensitivity factors determined on reference materials of a composition similar
to the material (bulk, layer, or particle) under investigation. Clearly, particle size and
other microdomain effects are of greater importance for these techniques than for the
GDS techniques and HF-plasma SNMS that consume sample material from mm² to cm²
sized areas. This point will need further investigation after preparing the CRM’s.
5. ECONOMIC AND SOCIAL BENEFITS
The economical prosperity of Europe depends on the quality and reliability of the
produced goods and on the production costs. In most cases the quality of the product
depends on the materials used. In the production processes analytical methods play a
vital role in checking the composition and quality of the product. The analysis needs to
be precise, accurate and as rapid as possible. GD-OES and HF-plasma SNMS can play
in a major role in the rapid analysis of solid materials both for bulk analysis and for the
characterisation of surface layers which can vitally affect material performance.
Currently, about 60 - 80 European laboratories use GD-OES techniques available from
4 - 5 instrument manufacturers. Direct Current (DC) -GD-OES has found a widespread
DC 1/00/Topic III.30/ Pg 4
use mainly for bulk analysis and for depth profiling in metallurgical and other
industries. Using the recently developed
HF-mode, the method can be applied for analysing a much wider field of materials of
high and increasingly important economical interest: decorative and protective coatings
on metals or non-metals; hard coatings on metals; lacquers, polymers, ceramics, glasses
etc. Up to now, the analytical results of DC- or HF-GD-OES measurements on these
materials is typically of qualitative nature. With CRMs becoming available, the
applicability of the method will be extended, and its power enhanced, because
quantification would be enabled.
HF-plasma SNMS has been invented and developed in Europe. It is employed in 14
European laboratories (4 companies, 6 institutes, and 4 universities) almost entirely in
the field of materials analysis and research and for the respective methodical
background. Like with the GDS techniques, the accuracy and reliability of HF-plasma
SNMS analyses of Carbides, Nitrides, Oxides, and mixed compounds are expected to
undergo a substantial improvement when appropriate CRMs will have become
available. This will enable European developers of new materials to refine their
production steps with respect to accurate elemental concentrations and depth profiles of
nm thick layers.
Evidently, the preparation of CRMs in Europe is no longer a national business.
6. SCIENTIFIC AND TECHNOLOGICAL OBJECTIVES
Based on the requirements outlined above, a set of bulk reference materials containing
different contents of nitrogen, carbon and oxygen - nitrides, carbides, carbonitrides,
oxides and oxynitrides - should be developed and produced in order to improve the
analytical potential of GD-OES, SNMS and other spectroscopic methods. Compositions
should range from a few percent to the highest stoichiometric contents of N, O and C in
order to obtain accurate and reliable calibration lines. Because of the background
discussed above the compositions of the reference materials should cover the range
given by typical technologically applied materials:
- B, Ti and Cr nitrides, carbides and carbonitrides (for hard, decorative, and
protective coatings),
- Al, Si, and Ti oxides and oxynitrides (for oxidation and passivation layers).
Bulk reference materials enabling multiple use are desirable for practical laboratory
work. These massive CRMs should be prepared by sintering or hot (isostatically)
pressing of pure ceramic powders.
The composites must be well characterised by different independent analysis methods.
The most important scientific tasks will lie in:
- The control of the CRM preparation processes mainly with respect to microcrystalline homogeneity and stoichiometric reproducibility and,
- The verification of stoichiometry and homogeneity with independent methods.
DC 1/00/Topic III.30/ Pg 5
References
[1]
[2]
[3]
[4]
[5]
[6]
[7]
[8]
[9]
[10]
[11]
H. Vetters, T. Hirsch, H. R. Stock, P. Mayr, Metalloberfläche 47 (1993) 6, 294-301
V. Hoffmann, Fresenius J. Anal. Chem., vol. 346, No. 1-3 (1993), 165-168
K. Marshall, D. Valesi, Materials World 10 (1995) 471-473)
"Glow Discharge Optical Spectrometry" ed. by R. Payling, D. Jones, A. Bengtson,
John Wiley & Sons, Chichester, New York, Weinheim, Brisbane, Singapore, Toronto,
1997
A. Bengtson, Spectrochimica Acta, vol. 49B, No. 4 (1994), 411-429
V. Hoffmann, H.-J. Uhlemann, F. Praessler, K. Wetzig, D. Birus, Fresenius J. Anal.
Chem. 355, 1996, 826-830
H. Oechsner in: H. Oechsner (Ed.), Thin Film and Depth Profile Analysis, Topics Curr
Phys 37, Springer, Berlin 1984
H. Jenett: Sekundärneutralteilchen-Massenspektrometrie (Plasma-SNMS), in: H. Günzler,
A.M. Bahadir, R. Borsdorf, K. Danzer, W. Fresenius, R. Galensa, W. Huber, M. Linscheid,
Lüderwald, G. Schwedt, G. Tölg, H. Wisser (Eds.): Analytiker-Taschenbuch 16.
Springer, Berlin, Heidelberg, New York 1997, pp. 43-117, and references therein.
W. Bock, M. Kopnarski, H. Oechsner Fresenius J. Anal. Chem. 353 (1995) 510
X. Ai, H. Bubert, H. Hutter, M. Gritsch, H. Börner, J. D. Sunderkötter, H. Jenett:
Al and Ti secondary neutral and secondary ion emission from oxide samples in the
high-frequency sputtering mode of HF-plasma SNMS. Fresenius J. Anal. Chem., in press
M. Griesser, H. Hutter, M. Grasserbauer, W. Kalss, R. Haubner, B. Lux: SIMS-analysis on
B, N, and C containing layers. Fresenius' J. Anal. Chem. 358 (1997) 293-296
DC 1/00/Topic III.30/ Pg 6
Addendum to the supporting document for all topics related to
the development of Certified Reference Materials (CRMs)
Introduction
Research in support of the development of CRMs is an objective of the Growth
Programme. The modality for this research is a shared cost action on RTD (cf work
programme Competitive and Sustainable Growth). The guidelines for the submission of
the proposal are laid down in the Guides for Proposers.
In addition to the requirements for research on a specific topic that are laid down in the
supporting document*, there are general requirements for the development of CRMs.
These requirements are described below and are in addition to the general requirements
for shared cost actions, as described in the guides for proposers and the model contract.
The requirements have been divided in 2 major parts:
I) Description of the work
This part concentrates on the technical requirements of the research as well as
the reporting requirements in view of the future certification.
II) Implementation of the objectives of the research
The research on CRMs consists of the development of the ability to produce and
certify reference materials that are fit for purpose. The planned exploitation of
the results has to aim at the production and certification of the reference
material(s) in accordance with prevailing international quality standards.
*
The dedicated call system enables the Commission to identify priority topics that have
been forwarded under the call for the expressions of interest. The supporting document
that has been used to evaluate the topic now serves as a reference document to the
proposers for the preparation of the proposal.
DC 1/00/Topic III.30/ Pg 7
I) Description of the work
Research on CRMs consists of the development of the ability to produce and certify
reference materials. The actual production of the CRM is not part of the research but is
part of the exploitation of the result(s).
In the first phase of the research project the certification strategy should be elaborated
(development of the materials and methods for characterisation), in the second phase of
the research project the ability to produce and certify should be demonstrated and
finally the specifications for the final CRM should be set.
The development of a CRM normally consists of 4 major parts:
1) development of the know-how required to produce (and package) the future CRM
2) development of the methods needed for future certification of the material
3) demonstration of the feasibility of the CRM production (production of a small batch
+ mimicking its certification)
4) reporting of detailed and realistic specifications for the future CRM
1. Development of the know-how required to produce (and package) the future
CRM






specify the sort of material that is most likely to meet both the targets laid down in
the supporting document and be suitably homogeneous, stable, safe to handle, and
acceptable in cost
identify the options available for selecting / preparing such a material
take into account special storage and / or transport requirements existing for certain
types of materials
develop of methods for production / selection and preparation, homogenisation,
stabilisation, protection and packaging of material as required, to enable the
production of a CRM which will be fit for purpose
if a material needs to be altered substantially (e.g. freeze drying), or when it is
artificially spiked with the substance of interest, it is necessary to check if the material
behaves in the same manner as the routine samples when applying the relevant
methods of measurement.
Ensure the availability of a suitable reconstitution procedure if a material will need
reconstitution
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2. Development of the methods needed for future certification of the material
Certification can be performed according to different criteria. The research will
define which certification route, following internationally recognised quality
requirements and standards, will be followed.
Certification on the basis of pure substances

If the CRM is a pure substance the preparation methods should be such that the
presence of impurities are reduced to a minimum. Additionally the substance should
be tested for impurities by carefully selected methods at least in two laboratories.
Certification on the basis of preparation data

When dealing with a synthetic CRM and a quantity which is directly related to (or
depends in a well-established way on) composition, examine if preparation under
metrological conditions and certification on that basis (e.g. using gravimetric data) is
possible
 Identify nevertheless a method of measurement that can be used as an independent
check for large errors
Certification on the basis of measurements - method-dependent quantities

If the quantity to be certified is defined on the basis of a specific (standard) sample
treatment or method of measurement, certification will be based on statistical
processing of results produced by a sufficient number of laboratories (e.g. 12 - 15),
which follow strictly the standard protocol but include all variability which is
allowed by the protocol (do not use common sources of calibrants, reagents, ...
unless these will be available to the future CRM users and prescribed in the
protocol). Such protocol may have to be developed
 Work may be necessary to achieve an acceptable level of reproducibility
Certification on the basis of measurements - method-independent quantities

As error-free, matrix-independent, calibration-independent methods are exceptional,
the basis for certification will usually be an agreement between different methods and
different laboratories, applied under conditions of independence which rule out the
risk of a common systematic error. Methods with a high potential for matrixindependence and/or calibration-independence (e.g. IDMS for determining
polyisotopic elements) should be included if available
 it may be necessary to perform a substantial collaborative method improvement (to
achieve the required level of agreement between methods and between laboratories),
or even research (method development) to achieve the required ability to measure.
Guidance for collaborative method improvement is given in the BCR Guidelines*
*
Guidelines for the production and certification of BCR reference materials, available from the
Commission on request (E. Michel, tel: 32/2-295.11.33, fax: 32/2-295.80.72, email:
ellen.michel@cec.eu.int )
DC 1/00/Topic III.30/ Pg 9
3. Demonstration of the feasibility of the CRM production

prepare a small batch of material, similar to that intended to be prepared as a CRM,
using the method intended to be used to prepare the actual reference material
 Check the fitness for purpose:
 form, shape or texture of the material; if applicable, contamination (air, moisture,
vapours, dust and dirt, micro-organisms etc.)
 homogeneity
 stability (the analyte / measurand as well as the matrix)
 safety of packaging when exposed to shocks, extreme temperatures and other possible
causes of damage during storage and transport
 ease of opening and use
 lyophilisation and reconstitution procedures
Guidance for homogeneity and stability testing is given in the BCR Guidelines.

Use the test batch to mimic the certification of a future CRM in a measurement
campaign, designed as a certification exercise (see BCR Guidelines)

If the results show that a CRM prepared and certified as in the test round is not good
enough, then the development work (1. or 2. above) must be recommended
4. Reporting of detailed and realistic specifications for the future CRM
The reporting requirements are set in the guidelines for reporting. In addition to the
Final Technical Report the coordinator should prepare an overview of all the results,
as foreseen in the Technical Implementation Plan. In this report the outcome of the
research that sets the boundaries for the future CRM production should be given
preferably in the form of a technical data sheet. It should contain the following
information:
 form / type of samples (with preference for individually packed portions for single
use)
 lyophilisation and reconstitution procedures
 specify bottling, labelling, packing, storage and transport requirements
 identify any legal restrictions on the transport of such material and need for safety
labelling, collect data for material safety data sheets
 magnitude of the quantity of interest (acceptable range)
 acceptable uncertainty on the certified value for an individual sample (this includes
at least: acceptable uncertainty on the mean value for the entire batch, and
acceptable level of inhomogeneity of the batch)
 method requirements (if the CRM is method dependent)
 acceptable magnitude of other quantities
 an estimate of the quantity of CRM that should be produced as well as an estimate
of the production costs.
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II) Implementation of the objectives of the research
As for all shared cost contracts the contractors are obliged to exploit the knowledge
arising from the project. In the case of research on CRMs the contractors are, among
others, obliged to assure that the CRM is produced and certified within a reasonable
time limit (article 10 of Annex II General Conditions of model contract).
The "Technological Implementation Plan" (TIP), which has to be prepared in any
RTD project of the 5th Framework Programme, shall explain the actions planned to
assure that results of the project will be exploited. In case of CRMs this TIP has to
outline the strategy for the CRM production, certification and marketing within a
reasonable time frame, at a reasonable cost and according to internationally
recognised quality requirements. A draft TIP has to be available at the project midterm. Options, ranging from production by the consortium to production by a third
party or the Commission, will be explored in consultation with the Commission
Services.