Reflection zone plate wavelength-dispersive spectrometer for ultra-light elements measurements.

We have developed an electron beam excitation ultra-soft X-ray add-on device for a scanning electron microscope with a reflective zone plate mulichannel spectrometer in order to analyse ultra-light elements such as Li and B. This spectrometer has high (λ/Δλ~100) resolving power in the energy range of 45 eV - 1120 eV. Metallic Li samples were examined and fluorescence spectra successfully measured. Energy resolution of 0.49 eV was measured in the ultra-low energy range using the Al L(2,3) line at 71 eV. High sensitivity of Boron detection was demonstrated on a B(4)C sample with layer thicknesses of 1-50 nm, detecting an amount of metallic Boron as small as ~0.57 fg.