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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.

Observations of semiconductor multilayers with backscattered electrons in a scanning electron microscope have been used to revisit the concept of resolution of the backscattering imaging mode. With the support of Monte Carlo simulations of beam specimen interaction, it has been

In this work, we report on a theoretical study of the contrast formation at Si/SixGe1−x interfaces in backscattered electron images of a scanning electron microscope. The contrast at the heterointerface is calculated for different atomic concentrations (0 < × < 1) and energies (E0 = 10 and 20 keV). The electron scattering phenomenon is simulated by employing a Monte Carlo method by using a single scattering approach. The signal intensity close to the interface shows a peak on the alloy side and a dip on the Si side. We explain this phenomenon by using the diffusion theory of the backscattered electrons. The spatial resolution increases by decreasing the Si concentration in the alloy side and by decreasing the beam energy.

Comparative studies on the ultimate spatial resolution of the Scanning Electron Microscope, using different components of the electron signal have been performed on specimens providing compositional contrast. By operating the microscope in conventional way as well as with a specifically designed set-up we have ascertained that the delocalized components of the signal provide a spatial resolution of the order of the beam size, even if the practical use can be limited by the noise. To amplify the contribution of the delocalized components of the signal, as backscattered electrons by a bulk specimen or forward scattered electrons by a thin specimen, we used a device consisting of a plate of a material with high secondary yield placed above or below the sample. An important practical implication arises from this study. A detecting system consisting of a standard Everhart-Thornley detector coupled with a converter of backscattered or transmitted electrons represents a high performance detecting device for low voltage observations.

The main factors affecting the spatial resolution of the scanning electron microscope have been analysed using a suitable inhomogeneous specimen consisting of semiconductor multilayers. Operating in secondary electron as well as in backscattered electron imaging mode, with the support of Monte Carlo simulations of beam-specimen interaction, it has been possible to achieve the following conclusions. All the backscattered or secondary electrons positively contribute to the image formation independently of their trajectories and specimen exit points. The resolution of the backscattered electron images depends only on the beam size and the signal to noise ratio. The generation volume of backscattered electrons affects the contrast but does not represent in itself a limit to the resolution. The contrast of secondary electron images of the semiconductor multilayer has essentially a compositional nature, being linked to the collection of secondary electrons produced by the backscattered ones. Moreover, using a converter of backscattered electrons in secondary electrons located underneath the pole pieces of the microscope objective lens, it has been demonstrated an improvement of the signal that allows a resolution equal to the electron beam size. This resolution cannot be obtained, operating in the same electron optical conditions, without the converter, due to the lower signal level.

This work investigates the use of an unconventional reference material to determine experimentally the Cliff-Lorimer factor for EDS quantitative analysis with a transmission electron microscope. The results demonstrate the equivalence of a bi-layer of pure gold on pure silver with respect to a binary alloy foil of the same elements. RF-sputtering is a suitable technique to prepare such reference materials that have a uniform thickness within a few percent tolerance. The availability of a calibrated set of similar reference materials would allow direct measurement of the k-factors for a large number of elements. This would avoid the errors due to the use of theoretical k-factors extracted from the compilations available in the literature. A new expression of the correction factor for X-ray self-absorption of the sample has also been derived.