Electronic structure analyses of BN network materials using high energy-resolution spectroscopy methods based on transmission electron microscopy

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    Abstract

    Electronic structures of boron-nitride (BN) nanotubes and a BN cone-structure material were studied by using a high energy-resolution electron energy-loss spectroscopy (EELS) microscope. A trial of the whole electronic structure study of hexagonal BN (h-BN), which consists of flat BN honeycomb layers, was conducted by a combination of EELS and X-ray emission spectroscopy (XES) based on transmission electron microscopy (TEM) (TEM-EELS/XES). The π and π+σ plasmon energies of BN nanotubes (BNT) were smaller than those of h-BN. The π+σ energy was explained by the surface plasmon excitation. The spectrum of a two-wall BNT of 2.7 nm in diameter showed a new spectral onset at 4 eV. The valence electron excitation spectra obtained from the tip region of the BN cone with an apex angle of 20° showed similar intensity distribution with those of BNTs. The B K-shell electron excitation spectra obtained from the bottom edge region of the BN cone showed additional peak intensity when compared with those of h-BN and BNT. The B K-shell electron excitation spectra and B K-emission spectra of h-BN were compared with a result of a LDA band calculation. It showed that high symmetry points in the band diagram appear as peak and/or shoulder structures in the EELS and XES spectra. Interband transitions appeared in the imaginary part of the dielectric function of h-BN experimentally obtained were assigned in the band diagram. The analysis also presented that the LDA calculation estimated the bandgap energy smaller than the real material by an amount of 2 eV. Those results of TEM-EELS/XES analysis presented that high energy-resolution spectroscopy methods combined with TEM is a promising method to analyze whole electronic structures of nanometer scale materials.

    Original languageEnglish
    Pages (from-to)531-537
    Number of pages7
    JournalMicroscopy Research and Technique
    Volume69
    Issue number7
    DOIs
    Publication statusPublished - 2006 Jul 1

    Keywords

    • BN cones
    • BN nanotubes
    • EELS
    • EELS/XES analysis
    • Electronic structures
    • Hexagonal BN
    • XES

    ASJC Scopus subject areas

    • Anatomy
    • Histology
    • Instrumentation
    • Medical Laboratory Technology

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