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Paper des Monats
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A layer of Sb atoms, implanted with an energy of 400 keV and a nominal dose of 5×1016 atoms/cm2 into a high purity silicon wafer, was certified for its areal density (atoms/cm2) using Rutherford backscattering spectrometry (RBS), instrumental neutron activation analysis (INAA) and inductively coupled plasma isotope dilution mass spectrometry (ICP-IDMS) and for its isotope ratio using INAA and ICP-IDMS. Excellent agreement between the results of the different independent methods was found. In the present work, the measurements of the homogeneity of the areal density of Sb, previously determined with RBS in spots having 1 mm diameter, are improved with synchrotron X-ray fluorescence analysis: Higher precision in even smaller sample spots allows to estimate a reduced inhomogeneity of the whole batch of samples of the order of only 0.4%. Thus the uncertainty of the certified value can further be reduced. Down to fractions of a chip with 0.3×0.4 mm2 area, the areal density is now certified as (4.81±0.06)×1016 Sb atoms/cm2, where the expanded uncertainty 0.06 (coverage factor k=2) corresponds to only 1.2%. The relative merits of the different analytical methods are discussed.
Electron probe microanalysis (EPMA) measurement of thin-film thickness in the nanometre range
(2002)
The thickness of thin films of platinum and nickel on fused silica and silicon substrates has been determined by EPMA using the commercial software STRATAGEM for calculation of film thickness. Film thickness ranged in the order 10 nm. An attempt was made to estimate the confidence range of the method by comparison with results from other methods of analysis. The data show that in addition to the uncertainty of the spectral intensity measurement and the complicated fitting routine, systematic deviation caused by the underlying model should be added. The scattering in the results from other methods does not enable specification of a range of uncertainty, but deviations from the real thickness are estimated to be less than 20%.
Naturwissenschaftliche Informationen, insbesondere die chemische Zusammensetzung der Objekte, können Hinweise auf die Hintergründe der Objektherstellung liefern, die der alleinigen kunsthistorischen Begutachtung verborgen blieben. Es können nicht nur Fragen nach dem Prozess, Zeitpunkt und Ort der Herstellung beantwortet werden. Die chemische Analyse gibt auch Hinweise auf Ereignisse und Veränderungen, die erst nach der Fertigstellung des Objektes erfolgten. So werden Alterungsphänomene oder historische Überarbeitungen und Restaurierungen aufgedeckt, aber auch Konservierungsstrategien zur Erhaltung der Kunstwerke unterstützt. Durch den technologischen Fortschritt im Bereich der röntgenanalytischen Methoden, die berührungsfrei, ohne Probennahme und ohne Schädigung für das Untersuchungsobjekt arbeiten, erschließen sich dem Analytiker erstmalig Möglichkeiten, auch sehr wertvolle und fragile Objekte zerstörungsfrei zu untersuchen.
Spatially resolved X-ray fluorescence analysis using synchrotron radiation (SR-XRF) at the wavelength shifter beamline, BAMline, at BESSY was used to investigate Renaissance silverpoint drawings as it is extremely sensitive, non-destructive and can be carried out in air using an excitation spot in the hundred micrometer range.
This paper deals with first results of the study of silverpoint drawings of Albrecht Dürer (14711528) belonging to the sketchbook that Albrecht Dürer used during a travel to the Netherlands in 1520/21. These results are compared to a PIXE study performed on drawings from the same sketchbook.
The minor element composition of the silverpoint used for the drawings in the sketchbook was (10.6 ± 3.5) wt.% of Cu and traces of Zn. Mercury was found in the marks but does not belong to the initial composition of the silverpoint as it is attributed to an alteration phenomenon. One drawing of the sketchbook represents an exception. It consists of silver marks containing an additional minor element, Zn, in the marks and was, therefore, created with another silverpoint, probably at a different time than the other drawings.
Synchrotron-induced X-ray fluorescence (Sy-XRF) analysis was used to study the chemical composition of precious Renaissance silverpoint drawings. Drawings by famous artists such as Albrecht Dürer (14711528) and Jan van Eyck (approximately 13951441) must be investigated non-destructively. Moreover, extremely sensitive synchrotron- or accelerator-based techniques are needed since only small quantities of silver are deposited on the paper. New criteria for attributing these works to a particular artist could be established based on the analysis of the chemical composition of the metal points used. We illustrate how analysis can give new art historical information by means of two case studies. Two particular drawings, one of Albrecht Dürer, showing a profile portrait of his closest friend, Willibald Pirckheimer (1503), and a second one attributed to Jan van Eyck, showing a Portrait of an elderly man, often named Niccolò Albergati, are the object of intense art historical controversy. Both drawings show inscriptions next to the figures. Analyses by Sy-XRF could reveal the same kind of silverpoint for the Pirckheimer portrait and its mysterious Greek inscription, contrary to the drawing by Van Eyck where at least three different metal points were applied. Two different types of silver marks were found in this portrait. Silver containing gold marks were detected in the inscriptions and over-subscriptions. This is the first evidence of the use of gold points for metal point drawings in the Middle Ages.
The first hard x-ray beamline at BESSY II has been installed by BAM and PTB at a superconducting 7 T wavelength shifter. The main optical elements of the beamline are a double-multilayer monochromator and a double-crystal monochromator. Depending on the application, the two devices are used separately or in-line. The main applications of the monochromatic radiation with photon energies up to 60 keV are x-ray fluorescence analysis, micro computed tomography, x-ray topography, detector calibration and reflectometry. Calculable undispersed radiation up to 200 keV is available for radiometric applications.
Synchrotron radiation (SR) has been used in recent years as an excellent excitation source for X-ray fluorescence spectrometry. SR offers, in contrast to conventional X-ray sources, highly brilliant polychromatic, polarized radiation with which micro-domain X-ray fluorescence spectrometry becomes possible. A feasibility study of utility, conducted at BESSY (Berlin) and at DELTA (Dortmund), both synchrotron facilities of the third generation, to evaluate the use of wavelength dispersive X-ray fluorescence spectrometry in combination with synchrotron radiation is presented. First results for material analysis, obtained by combining the synchrotron radiation and a commercially available spectrometer commonly attached to a scanning electron microscope, are presented. The spectrometer, of the linear type, uses curved focusing Bragg-crystals of the Johann type which leads to a high spectral resolution up to 3 eV. Examples of micro-domain analyses are presented and compared with those obtained by synchrotron radiation induced energy dispersive X-ray fluorescence.