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A calibration procedure for the detection efficiency of energy dispersive X-ray spectrometers (EDS) used in combination with scanning electron microscopy (SEM) for standardless electron probe microanalysis (EPMA) is presented. The procedure is based on the comparison of X-ray spectra from a reference material (RM) measured with the EDS to be calibrated and a reference EDS. The RM is certified by the line intensities in the X-ray spectrum recorded with a reference EDS and by its composition. The calibration of the reference EDS is performed using synchrotron radiation at the radiometry laboratory of the Physikalisch-Technische Bundesanstalt. Measurement of RM spectra and comparison of the specified line intensities enables a rapid efficiency calibration on most SEMs. The article reports on studies to prepare such a RM and on EDS calibration and proposes a methodology that could be implemented in current spectrometer software to enable the calibration with a minimum of operator assistance.

Ten low sulphur fuel oils LSFO (sulphur content between 5 and 72 mg kg−1) were tested with a low-NOx burner. Metal dusting attack on flame recirculation tubes made of the Ni-base alloy Alloy 601 was observed for seven of the fuels. The concentrations of O2, CO, CO2, CxHy and H2 close to the inner surface of the flame tubes were measured during burner operation. In the region where the tubes were attacked, a high concentration of hydrocarbons was found giving a carbon activity well in excess of 1. The role of sulphur was investigated by electron probe analysis of the amount of sulphur adsorbed on the surface of the recirculation tube after operation. A low value was found and no significant differences were observed between areas that had and had not suffered from attack. It is concluded that no decisive evidence has been found for the inhibiting effect of adsorbed sulphur on the catalytic activity of surface sites.

Quantitative analysis by electron probe micro analysis (EPMA) is usually carried out by reference to materials of known composition (standards) but because of the low X-ray yield arising from electron bombardment of low atomic number elements there is a particular problem when analysing these elements. This paper addresses the problem by describing briefly the production and certification of reference materials for two elements, carbon and nitrogen. Cementite (Fe3C), a line compound, was chosen as a suitable material for carbon and γ′-Fe4N for nitrogen. The compounds were produced by, respectively, carburising or nitriding pure iron under carefully controlled conditions. Particular emphasis is placed on a homogeneity study, background correction methods and methodology validation using these reference materials. A linear relationship was established between the certified content of the material and zero. Certified values (6.69±k 0.13 wt% C and 5.77±k 0.094 wt% N) were assigned for the composition, where k is the coverage factor.

A steel sandwich sheet was produced by a high temperature dipping process. An unalloyed steel was used as substrate and an alloyed steel as coating. At the interface of the sandwich sheet a good bonding between the two different steels could be achieved by a bonding process, which was caused by the formation of a diffusion induced liquid phase. Since the bonding is connected to the formation of the liquid phase at the interface, this is similar to a conventional welding process. This welding process was investigated at the interface of well and partially bonded specimens. Based on these investigations the bonding mechanism could be explained.

A common problem in depth profile measurement is the calibration of the depth scale. The new technique of sputter assisted electron probe microanalysis offers the possibility of calculating the composition as well as the depth scale solely from the acquired X-ray intensity data without further information, e.g. sputter rates. To achieve a depth resolution that is smaller than the depth of information of the electron probe, i.e. 0.1–1 μm, special deconvolution algorithms must be applied to the acquired data. To assess the capabilities of this new technique it was applied to a Ti/Al/Ti multilayer on Si under different measurement conditions. Quantitative depth profiles were obtained by application of a deconvolution algorithm based on maximum entropy analysis. By comparison of these profiles with AES depth profiles and AFM roughness measurements, it was shown that the limiting factor to the achievable depth resolution is the occurrence of surface roughening induced by the sputtering process rather than the relatively large depth of information of the electron probe. We conclude that for certain applications sputter-assisted EPMA can be regarded as a valid depth profiling technique with a depth resolution in the nm range.

Performing X-ray microanalysis at beam energies lower than those conventionally used (

Heat-insulating coatings on window glass consist of thin metallic films embedded in thin dielectric films. Such multilayer systems are produced commercially by physical vapour deposition in a continuous technique. For process control as well as for the development of new types of multilayer systems, surface-sensitive methods of analysis are essential to characterize the structure of the coatings in terms of the thickness and chemical composition of each layer. The present work reports on the first application of electron probe microanalysis (EPMA) in depth profiling of a complex heat-insulating coating on floatglass. It is well known that conventional EPMA is a powerful tool in microbeam analysis to quantify chemical compositions with high accuracy and to detect rather low concentrations even for light elements (B-F). However, the large information depth of x-rays (∼0.1-1 μm) limits the applicability to depth profiling. A great step forward in depth profiling in the submicrometre range was achieved by combining EPMA with surface removal by a sputtering procedure. Two various techniques can be applied: measurement of the emitted x-rays by scanning the electron beam across a sputter crater edge; or sputtering the material in situ with an integrated ion gun. In this work we succeeded in quantifying the film thickness (mass coverage) and chemical composition of each single component of the heat-insulating structure. The great advantage of the new method is its ability to determine the depth scale, as well as its remarkable detection limit. For example, in a depth of 100 nm a thin NiCr layer ∼1 nm thick could be detected. The Ni/Cr ratio of the layer was determined reproducibly to be 85: 15. The minimal thickness that could have been detected was estimated to be 0.15 nm.

Deuterium and hydrogen containing co-deposited layers formed on plasma facing components at the TEXTOR tokamak were characterised by a number of techniques including surface analysis methods and thermal desorption spectrometry. The aim of the investigation was to determine the composition and structure of the layers prior and after their exposure to air at elevated temperatures of 300°C and 550°C. The impact of the oxidation on the deuterium content and distribution in the surface region and in the bulk of PFC was addressed. The initial deuterium-to-carbon concentration ratio was in the range 0.04–0.06 in the flaking layers on top of the PFC and up to 0.17 on their side surfaces. The oxidation at 300°C for 2 h resulted in partial removal of the deuterium, especially from thin or loosely bound layers, but the release was not accompanied by the change in the deposit structure. The content of plasma impurity atoms in the layers was also not influenced by the exposure to air. Following the oxidation at 550°C partial powderisation of thick, flaking films was observed.

Wall conditioning and especially wall coating procedures like boronization or siliconization are indispensable for present day machines. They are also needed for future steady state plasma devices with superconducting coils and permanent magnetic fields like ITER. However, since important standard conditioning techniques like Plasma Chemical Vapor Deposition (PCVD), based on dc-glow discharges, are not compatible with those fields, new techniques have to be developed. This paper reports on first ion cyclotron range of frequency (ICRF)-assisted in situ deposition of a boron and carbon containing layer of relevant thickness onto the first wall of a tokamak. The new method is called ion cyclotron coating (ICC) and is based on ICRF plasma production in gas mixtures containing appropriate reactive precursor molecules. The new method is compatible with the magnetic field since it depends on its presence in order to produce a plasma. The geometrical arrangement of necessary facilities and their characteristic parameters for ICC in TEXTOR-94 will be described as well as the experimental procedure. The ICC-process itself and the properties of the produced layer will be presented.

Homogeneous films of metastable Cu 3 N were deposited on Si- wafers at 90°C by means of reactive magnetron sputtering ion plating. Under electron bombardment with a focused beam at high current (> 700 nA, 15 keV) these films transform into metallic Cu and N 2 . The depletion of N was measured quantitatively by EPMA. Structures with a lateral size of 2 μm consisting of metallic copper were written into the Cu 3 N films. AFM surface scans revealed a vertical growth of the columnar grains of the Cu 3 N film due to the electron bombardment.

The paper describes the investigation of the progressive erosion of an a-B:D coated test piece during 22 pulses in the SOL of TEXTOR-94. Time resolved observations by colorimetry reveal that the erosion proceeds in steps: during an intermediate phase the rates do not exceed ∼ − 1.5 nm/s. Thereafter they jump to about −6 nm/s. This is due to carbon incorporation and triggered when the concentration approaches ∼ 40%. The changing composition may influence the ratio of the BII/CII emission near the surface. The process ends with a carbon rich layer on the remnants of the boron film. Combination of different investigations (AES, NRA, EPMA) results in a preliminary model description.

The remarkable features of modern EPMA techniques are high sensitivity for very small coverages of thin films on substrates (10 14 cm -2 ) and a reliable quantitative determination of elemental compositions. The present work makes use of these features and combines them with ion sputtering of the sample surface to extend the capability of EPMA to real in-depth analysis in the submicron range. The general theoretical background of this EPMA-sputter-depth profiling is worked out and on the basis of a Monte-Carlo simulation model a technique was developed to reconstruct surface near depth profiles by a multiple thin film model. As a result, this new approach is able to determine depth profiles quantitatively with regard to both composition and the real depth coordinate in terms of mass coverage. After having been verified at an artificial layer system of different Ti-Al-N-O-compounds the new technique was used to study oxide scales which were grown on technical hardcoatings of the type Ti 1 - x Al x N with different fractions x. Despite the roughness of the oxide scales and although the structure of different oxide types was interlocked the variation of the elemental composition with depth could be worked out quantitatively with a relative accuracy of 10%. Additionally a reasonable evaluation of the depth coordinate in mass coverage could be attained, the results of which could be assessed by SEM imaging of the scales in fractured samples.

In order to compare thin-film electron probe microanalysis (EPMA) and Auger electron spectroscopy (AES) regarding reliability in quantifying chemical compositions of Ti-Al-O-N coatings with depth, a multilayer was prepared on a silicon wafer by using reactive ionized cluster beam deposition technique. Within a total thickness of about 25 nm the composition of the multilayer varied step by step from Ti-Al-O-N at the bottom to Al-O at the top. AES and, as an innovation, EPMA crater edge profiling was applied to measure the composition with depth. For quantification special thin-film EPMA techniques based on Monte Carlo simulations were applied. The chemical binding states of Al and Ti with depth were analysed using a high resolution energy analyser (MAC 3) for the AES investigations working in the direct mode. According to the deposition procedure the concentration profiles of the components varied with depth for both AES and EPMA measurements. AES provided a better depth resolution than EPMA. To get a true calibration of the depth scale an in-situ measurement method like an optical interferometry will be required. Assuming that the relative sensitivity factors are available AES depth profiling delivers concentration profiles with good accuracy. The new EPMA application provided quantitative depth profiles concerning concentration and coverage. For EPMA crater edge profiling the coating needs to be deposited on a foreign substrate because depth distributions of elements being present in both the layer and the substrate cannot be resolved. The combination of AES-depth profiling with EPMA crater edge profiling techniques is a powerful tool to analyse heterostructures quantitatively.

In the present work EPMA combined with Monte Carlo simulation was applied to investigate implanted gallium depth distributions in ZnSxSe1−x layers. The layers of about 1 to 4 μm thickness were grown by MOVPE on (100)-GaAs substrate. The overlap of the Ga and zinc L X-ray spectra and the low gallium net count rates were overcome by stripping the spectra of non implanted layers and by applying appropriate beam currents and counting times. Capabilities and limitations of the EPMA technique as applied to depth profile analysis are demonstrated.

Calibrated x-ray intensities of arsenic and gallium, implanted with various ion-energies and doses into silicon, were measured over a wide range of electron-beam energies and angles of incidence. For the first time Monte-Carlo (MC) simulation was applied to evaluate the EPMA-data with respect to depth-profiles parameters, particularly at non-normal electron incidence. Accurate agreement between MC-simulated and measured κ-ratios was obtained in the whole range of excitation conditions applied. The resulting range parameters determined from the EPMA data agree closely with those obtained by other authors from RBS or NAA but like these they show systematic deviations from theoretical predictions

Optoelectronic devices in the blue spectral region require doped ZnS x Se 1− x layers for electrical confinement and optical waveguilding. Since ion implantation is often used to realize heavy doping in thin layers, we implanted gallium ions with different doses and energies into ZnSe and ZnS x Se 1− x ( x ≤ 0.4) layers, grown by metalorganic vapor phase epitaxy (MOVPE) on GaAs. Rapid thermal annealing was performed after SiO 2 capping. For characterization, we used electron probe micro-analysis (EPMA), photoluminescence (PL) at 11 K, Raman spectroscopy, far infrared reflectivity (FIR) and Hall measurements. In ZnSe, the Ga depth profiles remain nearly gaussian after annealing, indicating weak diffusion. PL shows that both the overall intensity and the ratio of excitonic to deep centre emissions are maximum for annealing at 850°C (30 s), implying optimum crystalline quality and maximum carrier concentration. In addition, the conductivity is maximum (10 Ω -1 cm -1 ). However, FIR reveals a heavily doped layer at the GaAs interface, which is assigned to the annealing-induced Zn diffusion into the substrate. Furthermore, the PL spectra show donor-acceptor pair (DAP) transitions which can be attributed to shallow acceptors due to complexes of Ga and intrinsic defects. With increasing ion dose the free carrier concentration saturates at 4 × 10 17 cm -3 probably due to self-compensation caused by zinc vacancies (V Z n ). For ZnS 0.3 Se 0.7 , EPMA measurements show a diffusion of the Ga towards the surface, while S- and Ga-rich surface defects appear during annealing. After implantation the PL spectra show deep level emissions at 2.08 and 2.35 eV, which were assigned to [Ga Z n − V Z n ] complexes and to Zn S e . Optimum annealing seems to occur at 850°C for 30 s, resulting in a maximum PL intensity with strong DAP and excitonic contributions. Similar behaviour was observed for ZnS 0.4 Se 0.6 . Up to now, due to the diffusion and compensation, the implanted and annealed ternary layers remain semi-insulating.

Parameters of the diffusion of N (up to 0.3 wt.%) in austenitic stainless steels (12 to 19 wt.% Cr, 12 to 16 wt.% Ni, up to 2 wt.% Mo) were determined within the temperature range of 1283–1573K. The small concentration gradients of N were successfully investigated using (1) mechanical serial sectioning technique in combination with either chemical N analysis or X-ray precision lattice parameter determination, and (2) measurements on microsections by means of either electron probe microanalysis or Kossel technique. The diffusion coefficients of N were found to be independent of its concentration. The alloying elements Cr and Mo reduce the N diffusivity in austenitic stainless steels which on the other hand is increased by Ni.

For the determination of diffusion coefficients by using the model “diffusion into a plate” methodical examinations were carried out on samples of austenitic steel that had been nitrided in their marginal zones for 1.5 h at 1523 K. For recording of the concentration of N as a function of the distance from the surface electron-probe microanalysis (EPMA) and the precision determination of the lattice parameters by Kossel technique were applied. Both methods yield comparable results.

For boron carbide the limit of the homogeneity range at the carbon-rich side has not yet been firmly established. During the last 20 years carbon-rich limiting compositions have been reported corresponding to B43C (i.e. “B13C3”), B4.0C (i.e. “B12C3”) and B3.6C (i.e. “B11C3”). By means of quantitative electron probe microanalysis (EPMA) the composition of the boron carbide phase in the following samples has been determined: 1. (i) boron-carbon diffusion couples, prepared by hot isostatic pressing (HIP) of the pure elements at above 2000 °C; 2. (ii) fused, regular boron carbide, obtained by carbothermic reduction of boric oxide at above 2500 °C (ESK electrofurnace process); 3. (iii) dense boron carbide compacts made by pressureless sintering of carbothermic boron carbide powder or by HIP of magnesiothermic boron carbide powder at above 2000 °C. In each sample the carbon-rich limiting composition has been determined as B4.3C (18.8 at.% C) which corresponds to B13C2·C and is probably a solid solution of carbon in B13C2. The B12C3 and B11C3 compositions could not be found. For quantitative analysis a standard sample has been used, which was obtained by arc melting the pure elements with a B: C atomic ratio of 4.39. Also indirect B: C atomic ratio determinations via chemical analyses of crushed samples have produced evidence to support the limit 4.3 found by EPMA.

The first wall of the fusion device TEXTOR at the Forschungszentrum Julich has been coated in situ with an amorphous hydrogen rich carbon/boron film (a-C/B:H) which reduces plasma impurities caused by the plasma surface interaction. The results of the coating process of the 35 m2 large inner wall surface have been controlled by a recently developed modification of the quantitative electron probe microanalysis, which has been applied to 12 samples from specified positions inside the tokamak. The quantification itself is based on a Monte Carlo simulation of electron trajectories providing very accurate results for X-ray intensities emitted by elements present in the electron bombarded sample. The Monte Carlo results are used in the present work to calibrate the measured X-ray intensities emitted by boron and carbon from the a-C/B:H layers deposited on pure silicon substrates. As a result the total deposited mass of the layer per area unit as well as the composition of the layers (except hydrogen) could be determined very accurately. The relative errors were less than 7%. The limit of detectability were found to be in the range of one monolayer for boron as well as for carbon.

Electron probe microanalysis (EPMA) has developed over the past 35 years into a versatile and reliable tool for the quantitative analysis of microregions in solids. Recently its applicability has been extended to the determination of the composition and the thickness of thin layers or multilayers on substrates. Precise and reliable quantifications by EPMA presuppose that the x-ray intensities are measured under optimized conditions. We discuss some of the important aspects concerning the exact measurement of x-ray intensities with signal properties. The topics covered range from size of the excitation volume and aspects of the generation, absorption, and emission of x-rays to instrumental stability, optimization of instrumental parameters, and sources of errors in EPMA.

The high temperature superconductor YBa2Cu3O7−x has been studied by quantitative electron probe microanalysis (EPMA). After investigation of appropriate standards and choice between three different matrix correction methods this technique provides very accurate analytical results including those for oxygen. The quantitative results even allow the determination of the stoichiometry with deviations less than 2% relative. The application of computercontrolled EPMA is demonstrated by the characterization of the microstructure of a ceramic Y-Ba-Cu-O sample. Finally the properties of copperL2 andL3 valence band spectra are presented for compounds with copper in different valence state.

In order to maintain the thermo-mechanical durability of ITER it is proposed to castellate the interior surface of the first wall and divertor by splitting them into small-size cells [W. Daener et a]., Fusion Eng. Des. 61&62 (2002) 61]. A concern is the accumulation of fuel in the gaps of the castellation. In TEXTOR, molybdenum limiters were exposed in the scrape-off layer (SOL) plasma to assess fuel accumulation. The first limiter was exposed under deposition-dominated conditions. Carbon deposits were formed both on top surfaces and in the gaps. About 0.12% of the impinging D-fluence was found in the gaps. Another castellated limiter was exposed under erosion-dominated conditions. Deposited layers were found only on the plasma shadowed areas of the gaps. A significant amount of molybdenum from the limiter was found intermixed in the deposit. The gaps contained similar to 0.03% of the impinging D-fluence. Modeling was performed to simulate carbon transport into the gaps. QC 20131120

A solar control coating was analysed by different methods of surface analysis with respect to the layer sequence and the composition and thickness of each sublayer. The methods used for depth profiling were Auger electron spectroscopy, electron probe microanalysis, secondary neutral mass spectroscopy and secondary ion mass spectroscopy based on MCs+. The structure of the coating was unknown at first. All methods found a system of two metallic Ag layers, embedded between dielectric SnOX layers. Additionally, thin Ni-Cr layers of 1–2 nm were detected on top of the Ag layers. Thus the detected layer sequence is SnOX/Ni-Cr/Ag/SnOX/Ni-Cr/Ag/SnOX/glass. The Ni:Cr ratio in the nm-thin layers could be quantified by every method, the Cr fraction corresponding to less than one monolayer. We compare the capabilities and limitations of each method in routinely investigating this solar control coating. Importance was attached to an effective investigation. Nevertheless, by combining all methods, measuring artefacts could be uncovered and a comprehensive characterisation of the system was obtained.

Electron probe x-ray microanalysis is capable of the sensitive detection and the reliable quantification of small (partial)mass coverages on a submicron scale. To improve depth profiling so as to give reasonable depth resolution, the technique can be combined with a sputtering process. This paper presents theoretical aspects concerning the experiment of EPMA sputter depth profiling and the evaluation of the measured data. By means of a Monte-Carlo-Simulation program sputter-intensity profiles for multilayered systems can be calculated. It is shown that the calculated intensity-sputter profiles provide more information about elemental depth distributions than those obtained by the more common EPMA-method of electron beam energy variation.

Electron probe x-ray microanalysis (EPMA) has been developed into a reliable technique for surface layer analysis but, due to the relatively large depth of information, it cannot yet be applied to resolve complex depth distributions, i.e. layers with concentration gradients or complex multilayer structures.

This paper presents a review of developments in thin film analysis by EPMA during the last 15 years and reports on the capabilities and limitations of the technique when applied to the quantitative analysis of thin coatings, multilayers and oxide layers. During the development of thin film EPMA it was always intended to apply EPMA to the analysis of elemental depth distributions in the submicron range. It is pointed out that the technique of electron beam energy variation is clearly limited to cases where some pre-information on the structure of the material or the shape of the depth profiles is available. For real EPMA-depth profiling in the depth range of 1 µm to a few µm, mechanical bevelling of the sample and analysis with low, carefully chosen beam energies is recommended as a useful technique, which is demonstrated here by application to a multilayered hard coating.

The objective of this work is to determine the materials properties of thin layers typically deposited for wall conditioning in fusion devices. As reference material, a sequence of thin amorphous hydrogenated silicon layers with different thicknesses were produced on polished glassy carbon by Plasma Chemical Vapour Deposition PCVD. The films were characterised using AES, AFM, EPMA, ellipsometry, interference fringe analysis and RBS. A second aim was to study the accuracy and reliability of EPMA and RBS measurements. The techniques applied provided values for refractive index, absorption coefficient, roughness, thickness and elemental areal density. From the latter two, the density of the film could be determined. It turned out that the density derived by combining the results from different techniques was in good agreement. For the range of thickness investigated, the combination of ellipsometry and EPMA gave the most consistent values for the density with a maximum uncertainty of ±5%.

Approximately 70 nm thick films of non-conducting (Y2O3)x(ZrO2)1-x (x ≈ 0.1) were deposited on Si(100) substrates by electron beam evaporation. Subsequently, electron probe microanalysis (EPMA) was applied to determine the yttrium content. Experimental efforts were made to assess the accuracy of the EPMA results and to determine the detection limits of the technique. The intensities of the characteristic X-ray lines Y Lα, O Kα, Zr Lα and Si Kα, emitted from the electron-beam excited samples, were measured with a Jeol JXA-50 A microanalyzer for beam energies of 4, 7, 10, 14 and 20 keV. Charging of the films did not occur. The intensities were calibrated with corresponding intensities of Y3 Fe5 O12 , Zr and Si standard samples. The number of Y, Zr and O atoms per cm2 were determined independently for each beam energy by comparing the measured intensities with calculations of a Monte Carlo simulation program. The number of atoms per cm2 were determined with an accuracy better than 5% and the uncertainties of the Y contents were below 0.25 atomic percent. The detection limits of the Jeol JXA-50 A for Y, Zr and O on a silicon substrate were 2.3, 4 and 13· 1014 atoms per cm2, respectively, at 200 nA beam current and 1 min counting time.

In the present paper anomalies in the background at low spectrometer angles are investigated. It is found, that totally reflected low-energy characteristic X-rays cause this effect. The critical angles of total reflection are determined for a set of X-ray lines. It is shown, that total reflection may occur with all analyzing crystals which are used in electron probe microanalysis.

Electron Probe Microanalysis (EPMA) is a well-established technique for the quantitative elemental analysis of solid materials on a microscopic scale. For a reliable quantification of the characteristic x-ray measurements an appropriate set of standards would be necessary, to cover all possible elements and compounds. In practice only a limited set of pure elements or compounds is available. Therefore for a general use of the technique the relation between the emitted x-ray intensity and the weight fraction c i of the emitting element in the sample should be known for all elements and their possible combinations in compounds. Following the work of Castaing [1] one can write the general form for the emitted primary intensity of element i-radiation: (1) Q i is the ionization cross section for the ith level, c i the weight fraction of element i, ω i , the fluorescent yield of the ith level, ρz the mass depth and χ i = (μ/ρ) cos θ with the absorption coefficient μ/ρ and the take-off angle θ. φ i is the absolute distribution of the characteristic x radiation excited by the electrons in a depth ρz of the target.

Conventionally, x-ray microanalysis on scanning electron microscopes (SEM) with energy dispersive spectrometers (EDS) has been performed with relatively high primary energies (>10 kv). for most samples this results in reasonably good separation of the generated x-ray line series from different elements enabling unambiguous identification and therefore accurate qualitative analysis. Under these circumstances it is widely accepted that quantitative analysis of polished bulk samples is possible on a routine basis with relative errors around 1-5% and detection limits of the order of 0.1%.However, in order to address the analysis requirements of new advanced materials with sub-micron features, there is growing interest in performing x-ray microanalysis at low beam energies(

The interaction of a focused beam of monochromatic electrons with a solid sample is a complex many-particle problem, which cannot be fully described by analytical methods. But already in the early sixties trajectories of single electrons were simulated numerically on computers (1,2,3). This method was called Monte Carlo simulation (MC). Sequential simulation of some thousand trajectories accumulates a set of data, sufficient to provide information about -fraction of backscattered electrons,-fraction of transmitted electrons in case of thin film samples,-ionization probability for certain electron shells as a function of sample depth,-calculation of x-ray intensities generated in or emitted from the sample,-energy distribution of backscattered electrons or of electrons in certain depth,-calculation of signal generation in samples with complex geometries. For all these applications the physical processes of electron - solid interaction needed to be described as realistic and accurate as possible, which was always - and is still - in contradiction to the limitations of existing theories, their applicability in such a complex problem, and of course to the limitations of computer capacities.

Redeposition of eroded carbon can form carbon-rich layers on the plasma facing components of experimental fusion devices. The trapping of hydrogen isotopes in these deposits may represent a potential safety hazard in T–D operated devices. Understanding the properties of these deposits, like composition, structure, chemical activity etc, is an important prerequisite to predict the hydrogen retention, and to develop in-situ removal techniques. Thick layers (~150 µm), which tend to flake off, were found on different wall components of TEXTOR-94 after long term operation (6110 discharges). Flakes with a size of a few mm2 had been removed from the main poloidal limiter. They have rough, bubbly appearance, and are porous but mechanically hard. The deposits were examined by SEM, NRA, EPMA, EDX, and OES. They consist of about 80%–90% carbon and incorporate non-uniformly distributed deuterium, Si, B and metals (mainly Fe, Cr, Ni, also as clusters). The D/C-ratio found in these flakes measured by TDS is 4 × 10-4. Baking the flakes in the air at 250°C reduces their thickness at a rate of about 1.2 µm/h, baking at 450°C gives a rate of about 2.6 µm/h. After baking the flakes turn to ash. The main residues are metals, B and Si, elements that do not form volatile oxidation products.

In its conventional application the electron probe microanalysis (EPMA) is a suitable technique for the quantitative microanalysis of samples, which are homogeneous inside the excited volume. Depending on the beam energy and the target composition the measured x-ray intensities are emerging from depths between about 50 nm and some microns. They contain an integral information about the composition of the excited volume. Nevertheless, the sensitivity of this technique also allows the detection of thin films on substrates with thicknesses even less than one monolayer. For such samples composed inhomogeneously near the surface, e.g. thin layers on substrates or sandwich structures, detailed quantitative informations can only be obtained when the integral information can be deconvoluted properly from the intensities. A necessary prerequisite to solve this problem is the exact knowledge of the depth distribution of the generated x-ray intensities ϕ(ρz) in samples which are inhomogeneous inside the excited volume. Up to now ϕ(ρz) is rather unknown for such samples.

In the last 35 years electron probe microanalysis (EPMA) has developed to a versatile technique for the quantitative analysis of materials on a microscopic scale. This development has been initiated by the pioneering work of Castaing in 1951 (1). Already in 1955 Castaing and Descamps have introduced a basic formulation for the absorption correction to quantify characteristic x-ray data (2). This correction already presumed the knowledge of the distribution ϕ(ρz) of the generated x-ray intensity as a function of the depth ρz inside the target. The authors presented the first experimental procedure to determine this distribution for pure elements by the so called sandwich sample technique. The results of this early work, obtained for several pure elements, became a standard in the field and many authors have examined their theoretical approaches or their Monte-Carlo simulations of ϕ(ρz) by means of these ϕ(ρz) data. In the following time further attempts of ϕ(ρz) determinations by experiments or by theoretical approaches, e.g. Philibert (3), became necessary because a general application of a matrix correction to the whole elemental range, detectable by EPMA, required a generalized analytical description of ϕ(ρz).

In the EPMA of soft x rays anomalies in the background are found for several elements. In the literature extremely high backgrounds in the region of the OKα line are reported for C, Al, Si, Mo, and Zr. We found the same effect also for Boron (Fig. 1). For small glancing angles θ, the background measured using a LdSte crystal is significantly higher for B compared with BN and C, although the latter are of higher atomic number. It would be expected, that , characteristic radiation missing, the background IB (bremsstrahlung) is proportional Zn by variation of the atomic number of the target material. According to Kramers n has the value of unity, whereas Rao-Sahib and Wittry proposed values between 1.12 and 1.38 , depending on Z, E and Eo. In all cases IB should increase with increasing atomic number Z. The measured values are in discrepancy with the expected ones.

Steel sheet today ranks among the highly developed products of Europe's steel industry. Given the increasing consumption and expanding range of applications of the coated steel sheet materials, it is becoming more and more important to know the surface properties. This applies both to the surface of uncoated steel sheet and to that of the metallic zinc and zinc alloy coatings. Current objectives of the steel makers are, in particular, knowledge of the chemical composition of the surface throughout the route of production, as well as targeted production control to achieve a defined composition. A producer or end user correlates the surface composition with technological, processing and service properties, and is hence interested in compiling and complying with defined supply specifications. Against this background, the modern analysis techniques used for the chemical characterisation of steel sheet surfaces take on a key function for product development and quality control. Currently, a multitude of possible analysis,techniques like EPMA, GDOES, SNMS, AES and ESCA are available for the chemical characterisation of surfaces. Within the framework of a European research project (ECSC - European coal and steel community), the suitability of such modern analysis techniques for the needs of the steel sheet producers, customers and users has been studied and adapted to the requirements involved. The following erticle - divided into four parts- will give a report about some analytical applications and the actual state of the art regarding microarea and surface analysis of steel sheet surfaces.

The intention of this work is the full characterisation of morphology, composition and structure of so-called intermediate layers in continuously galvanised steel sheets. These layers grow as a reaction product of the sheet with the liquid zinc which contains a few tenth % of mass fraction aluminium. Conventional methods of surface analysis combined with ion sputtering fail to resolve the layers because of extreme surface roughness of the zinc coating induced by the sputter process. Better access to the intermediate zones can be attained after carefully removing the zinc coating by etching or chemical polishing without attacking the layers. The uncovered layers can be analysed by EPMA, AES-line scanning and SEM. Especially an EPMA-thin film analysis technique turns out to be most suitable to analyse quantitatively the composition and stoichiometry of phases in the layer(s). Also layer thicknesses can be determined in terms of mass coverage. The results of these analyses are in good agreement with literature data from metallurgical and constitutional investigations. The applied techniques can be recommended for quality assurance and failure analysis in industrial production of continuously hot-dip zinc coated steel sheets.

Description d'une technique analytique pour identifier et quantifier l'azote dans les aciers allies. Utilisation de la spectrometrie Auger

Electron probe microanalysis of low energy X-rays has gained increasing importance over the last several years. On the one hand the proportion of analyses of boron, carbon, nitrogen and oxygen has increased, and on the other, interest in the use of low accelerating voltages, which reduces the depth of analysis, has grown. Here the utilization of low energy L- and M-lines is indispensable.

Ti/Al (10 nm/100 nm) bilayer contacts on Si-doped GaN were heat treated for 30 s at 600 and 650°C. The microstructure of the contacts was analysed by Auger depth profiling, SEM and EDX analysis and energy filtering TEM using electron spectroscopic imaging (ESI). The experiments show a strong interdiffusion of Al and Ti leading to the formation of an intermetallic compound. A complex, spatially inhomogeneous structure consisting of an Al-rich phase, a Ti–Al intermetallic compound and regions containing Al-oxide is formed, while the GaN is still covered by a thin, homogeneous Ti-rich layer. A thickness of 2.5 nm was obtained for the Ti-rich layer in the contact heat treated at 650°C. The combination of complementary results from Auger depth profiling, SEM analysis with EDX and ESI provides a comprehensive characterisation of the complex contact structure. The results will be discussed in terms of the contributions and specific advantages of the individual techniques.