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CCQM key comparison K-129 for the quantitative analysis of Cu(In,Ga)Se2 (CIGS) films has been performed by the Surface Analysis Working Group (SAWG) of the Consultative Committee for Amount of Substance (CCQM). The objective of this key comparison is to compare the equivalency of the National Metrology Institutes (NMIs) and Designated Institutes (DIs) for the measurement of mole fractions of Cu, In, Ga and Se in a thin CIGS film. The measurand of this key comparison is the average mole fractions of Cu, In, Ga and Se of a test CIGS alloy film in the unit of mole fraction (mol/mol). Mole fraction with the metrological unit of mol/mol can be practically converted to atomic fraction with the unit of at%.
In this key comparison, a CIGS film with certified mole fractions was supplied as a reference specimen to determine the relative sensitivity factors (RSFs) of Cu, In, Ga and Se. The mole fractions of the reference specimen were certified by isotope dilution - inductively coupled plasma/mass spectrometry (ID-ICP/MS) and are traceable to the SI. A total number counting (TNC) method was recommended as a method to determine the signal intensities of the constituent elements acquired in the depth profiles by Secondary Ion Mass Spectrometry (SIMS), X-ray Photoelectron Spectroscopy (XPS) and Auger Electron Spectroscopy (AES). Seven NMIs and one DI participated in this key comparison. The mole fractions of the CIGS films were measured by depth profiling based-SIMS, AES and XPS. The mole fractions were also measured by non-destructive X-Ray Fluorescence (XRF) Analysis and Electron Probe Micro Analysis (EPMA) with Energy Dispersive X-ray Spectrometry (EDX).
In this key comparison, the average degrees of equivalence uncertainties for Cu, In, Ga and Se are 0.0093 mol/mol, 0.0123 mol/mol, 0.0047 mol/mol and 0.0228 mol/mol, respectively. These values are much smaller than that of Fe in a Fe-Ni alloy film in CCQM K-67 (0.0330 mol/mol). This means that the quantification of multi-element alloy films is possible by depth profiling analysis using the TNC method.
For ten years µ-XRF (micro-focus X-ray fluorescence) analysis has been performed with SEM/EDS (scanning electron microscope with an energy dispersive X-ray detector) so that non-destructive analysis of elements at trace level concentrations below 100 µg g-1 becomes possible. This can be considered as a valuable completion of the classical electron probe microanalysis by EDS, an analytical method 'suffering' from rather poor limits of detection in the range of one to two orders of magnitude higher than those of µ-XRF. Based on a representative actual application, namely analysis of RoHS relevant elements at trace concentration levels, the performance of the rather new analytical method with respect to its limits of detection is systematically evaluated. CRMs (certified reference materials) specially prepared to support the quantitative XRF analysis of RoHS relevant elements were employed. On the other side, based on calculations of µ-XRF spectra according to a recently developed physical model the optimization of the analytical performance is also successfully undertaken.
The accurate knowledge of the properties of polycapillary X-ray semi-lenses has a significant influence on the quantitative results in a widespread field of applications involving microfocus X-ray beams. A routine procedure for the characterisation of a polycapillary X-ray semi-lens with a scanning electron microscope (SEM) having attached an energy dispersive spectrometer (EDS) is presented in this paper. A key issue of the procedure consists of fitting the semi-lens in front of the EDS for spectra acquisition. Relevant semi-lens parameters such as focal distance, full width at half maximum (FWHM) of the acceptance area, and transmission are determined in parallelising mode of the semi-lens. Special attention has been paid to the calculation of the transmission.
Determination of the efficiency of an energy dispersive X-ray spectrometer up to 50 keV with a SEM
(2009)
Both electron and polychromatic photon excitations (micro-focus X-ray source) at a scanning electron microscope (SEM) are used to determine the efficiency of an energy dispersive X-ray spectrometer up to 50 keV by means of a calibrated X-ray spectrometer and reference materials (RM) specially selected for this purpose.
Energy dispersive and wavelength dispersive X-ray spectrometry are used to determine the composition of a specimen in a scanning electron microscope (SEM) by electron probe microanalysis (EPMA). A valuable completion for the SEM is analysis by X-ray fluorescence (XRFA). The main advantage of this method consists in its low detection limit. XRFA with a SEM uses the same spectrometers as for EPMA, necessary are only an additional X-ray source for the excitation of fluorescence spectra and software for their evaluation. Recent developments of smart low-power X-ray tubes and X-ray optical components enabled the construction of compact X-ray sources with focussing properties as add-on for a SEM. For quantitative XRFA the source spectrum has to be known. For its calculation the X-ray production yields Y have been measured for the commonly used tube target materials Mo, Rh and W. The excitation spectra were calculated for a variety of source types and compared with respect to the achievable photon flux and its spectral distribution.