Ultra-Low kV EDS
Figure 10 : Nickel alloy coating containing chromium borides, carbides, and nitrides. X-ray maps were acquired at 7 kV: (a) SE image, (b) B K map, (c) C K map, (d) N K map, (e) Cr L map, and (f) Ni L map. The medium contrast phase in the boron X-ray map is boron dissolved in the Ni matrix.
Conclusion
Using low-incident beam energies for X-ray analysis reduces the scale of beam-sample interaction to as small as 10 nm, thus expanding the potential of EDS in the SEM to more closely match SEM imaging in recent high-resolution FEG-SEMs. In practice the substantial loss in signal intensity has been off set by the development of a new type of SDD detector optimized to collect X-rays when SEMs are operated at very low kV. These detectors maximize sensitivity to low-energy X-rays using windowless operation, low-noise electronics, and large non-circular SDD sensors that can be placed very near to the sample at a short working distance.
Figure 11 : Cell sample from a mouse kidney, fi xed and embedded in LR White embedding resin and sectioned with an ultramicrotome. Section was retrieved and put on a Si substrate chip. X-ray maps were collected using a windowless 100 mm 2 detector (X-Max Extreme). (a) SE image, (b) carbon map, (c) nitrogen map, and (d) oxygen map. Data courtesy of The University of Manchester, Electron Microscopy Centre.
to the lack of information about line energies and intensities, other factors such as mass absorption coefficients are poorly known, and discrepancies will cause large errors, for example, for lithium analysis [ 15 ].
2017 March •
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Acknowledgements T e authors would like to thank Mary Grace Burke, Greg McMahon, Arne Janssen, and Giacomo Bertali at the School of Materials, University of Manchester, and Fang Zhou and Luyang Han at Carl Zeiss Microscopy for supplying samples, microscope access, assistance, and data to illustrate
the applications examples shown in this study. We would like to thank Kaoru Sato of JFE Steel for his help, advice, and encour- agement for the development of ultra-low kV EDS. We would like to thank Pierre Hovington at Hydro Quebec for his data
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