Soft-X-ray emission spectroscopy based on TEM—Toward a total electronic structure analysis

The construction and basic performances of wavelength-dispersive soft-X-ray emission spectroscopy (SXES) devices attached to a transmission electron microscope were presented. An energy resolution of 0.23 eV was obtained at the aluminum L-emission energy. A Cu L-emission spectrum obtained showed four L-emission lines of Lα, Lβ, Ll and Lη. Angle-resolved measurements of boron K-emission spectra of hexagonal-BN (h-BN) were presented. It clearly showed anisotropic emission intensity of the transition from π-bonding state to 1 s core hole. B K-emission spectra of h- and cubic-BNs showed a difference in energy positions of σ-bonding peaks. An electron energy-loss spectrum of B K-edge and a B K-emission spectrum of cubic-BN were compared with a result of a LDA band calculation. It showed that high symmetry points in the band diagram appeared as peak and/or shoulder structures in those spectra. Interband transitions appeared in the imaginary part of the dielectric function of cubic-BN experimentally obtained were assigned in the band diagram. These results demonstrated a method to analyze the entire electronic structure of materials in the nanoscale using high energy-resolution spectroscopy methods based on transmission electron microscopy.