A New WDS Spectrometer for Valence Electron Spectroscopy Based on Electron Microscopy

A new WDS spectrometer for a transmission electron microscope has been constructed. This spectrometer can cover an energy region from 50 eV to 3800 eV by using four aberration-corrected gratings for flat-field optics. By using a newly designed and manufactured grating of JS50XL for 50-200 eV, soft-X-ray emission spectra of simple metals of Mg, Li, Al and Be were measured. Those intensity profiles correspond to partial density of states of valence electrons (bonding electrons) and also showed clear Fermi edges (top of the occupied state). At the Fermi edge of Mg-L emission(49.5 eV), an energy resolution was evaluated to be 0.16 eV. Si-L emission spectra of Si and TiSi2 show a difference in those intensity distributions, indicating different valenceelectron states for those materials. A comparison of B-K emission spectra of CaB6 and LaB6, which were obtained by using another grating of JS200N, is shown. A clear Fermi edge was also observed for LaB6 at about 187 eV with an energy resolution of 0.4 eV.