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Ultra-high Resolution Elemental Mapping of Si-core-C-shell Silicon Nanoparticles

Very low beam current and/or very short measurement time are needed for SEM-based EDS analysis of beam sensitive samples, such as Si nanoparticles. It is necessary to use low voltage to reduce the electron-sample interaction volume when high spatial resolution is required. For conventional EDS measurement, such analytical conditions are challenging since the induced X-ray yield is very low and thus demand very long measurement time. The consequence is beam-induced sample drift which affects the spatial resolution. 

EDS measurement performed with XFlash® FlatQUAD overcome these limitations. The unique geometry of the XFlash® FlatQUAD enables high detection sensitivity for low x-ray yield materials, giving high count rates at low probe currents. Thus, the XFlash® FlatQUAD detector is ideal for mapping beam-sensitive materials even with topography. 

This example presents a high-resolution map (pixel spacing of 2 nm!) of silicon nanoparticles. Mapping was done with a XFlash® FlatQUAD at 5 kV, 520 pA and 377 s acquisition time. The results indicate that the present nanoparticles are characterized by a silicon core (green) and a carbon shell (red). (Data courtesy:  S.Rades et al., Royal Society of Chemistry Advances, 2014, 4, 49577)

SE image of silicon nanoparticles on filter material
Element distribution map of silicon nanoparticles showing carbon in red and silicon in green
The linescan extracted from the element map in false colors indicates a diameter of 100 nm for the silicon nanoparticles