This book (Practical Electron Microscopy and Database) is a reference for TEM and SEM students, operators, engineers, technicians, managers, and researchers.
 

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The B (boron) K edges of the Be-B-bearing materials present a wide range of shapes, reflecting their different bonding types. Those bonding types affect the electrical resistivity of the materials. These properties include metallic in Be₂B (12 x 10^-6 Ω cm), BeB₂C₂ (17 x 10^-4 Ω cm), and BeB₂ (2 x 10^-2 Ω cm); semiconducting in Be_0.5B₆C (3.3 Ω cm); and insulating in BeB₆ and BeB₈ to 12 (1 to 6 x 10⁷ Ω cm) [1]. Figure 2653 shows the B K edges of some B-bearing materials. The increase in the energy of the edge onset reflects the transition from metallic in Be₃B to insulating in BeB₆. The first sharp peak at the B K edge of Be₂BO₃(OH) originated from the transitions of B 1s electrons to the unoccupied p states with π* character, while the B K edge of Be₃B is broad, lacking sharp features, originated from the overlap of bands due to its metallic conductivity.

Figure 2653 shows the B K edges of some B-bearing materials. The dotted vertical lines label the lowest energy onset in metallic Be_2.8B (≈Be₃B) and the greatest energy onset in insulating Be₂BO₃(OH), also see the red dots. The dotted lines have been set to the inflection points of the rising edges. Adapted from [2]

The core-loss edges in EELS are a projection of the atom resolved, partial density of states (PDOS) of the conduction band. However, in certain cases core-hole effects may modulate the features near the conduction-band onset.

[1] V. S. Neshpor and G. V. Samsonov, Inorg. Mater. 7, 45 (1971).
[2] Laurence A. J. Garvie, Peter R. Buseck, and Peter Rez, Characterization of Beryllium–Boron-Bearing Materials by Parallel Electron Energy-Loss Spectroscopy (PEELS), Journal of Solid State Chemistry 133, 347Ð355 (1997).