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- (mu-)XRF (1)
- Acceptance area (1)
- ED-EPMA (1)
- EDS (1)
- EDX (1)
- Energy-dispersive X-ray spectroscopy (1)
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- Micro-XRF (1)
It is a latent wish of any SEM/EDS (scanning electron microscope with an energy dispersive spectrometer) analyst to “see more” of the analyzed specimen, i.e. to improve the existing analytical figures of merit.
One key issue are the relatively poor limits of detection (not below 0.1 mass-%) provided by energy dispersive X-ray spectrometry (EDX) with the conventional electron excitation (ED-EPMA). This is a consequence of relatively low peak-to-background ratios and reduced energy resolution when compared to wavelength dispersive spectrometry (WD-EPMA). Recent technological developments make possible to equip the SEM with a wavelength dispersive spectrometer (WDS), so that
significantly better energy resolution can be attained. Also a relative new product that can be easily attached to a SEM/EDS system is a micro-focus X-ray source. Hence, it is possible to perform (micro-focus) X-ray fluorescence spectrometry (μ-XRF) and take advantage of the enhanced peak-to-background ratios (well suited for trace analysis). However, there are also some disadvantages: an increased measurement time and excitation with a high current in the 10s of nA range are usually required for WDS. μ-XRF provides more bulk information and poor limits of detection for light elements. By combining the advantages of these analytical techniques “seeing more” becomes possible.
A microfocus X-ray source mounted on the analysis chamber of an SEM was used to excite X-ray fluorescence spectra and to detect chemical elements with concentrations below the detection limit of the electron-excited X-ray spectra conventionally measured with SEM/EDS. An aluminium alloy and a hard material ceramics were analysed as representative examples. It is demonstrated that the combination of the three analytical methods: (1) SEM imaging for surface morphology characterisation; (2) electron-excited X-ray spectroscopy with its high spatial resolution for element analysis of inclusions or precipitates; and (3) X-ray fluorescence for the detection of elements with concentrations below 0.1 mass% considerably improves the performance of SEM/EDX analyses.
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.