Energy Band Structure, Optical Properties, and Spectroscopic Phenomena of a-BN

5 Energy Band Structure, Optical Properties, and Spectroscopic Phenomena of a-BN 

Variation of the states Tjand Tg (in the valence band) reflect a change in the interlayer ji-ji coupling [5]. The FLAPW method has also been used to study the bulk and surface electronic properties of a-BN [6, 7]. The treatment shows the absence of surface states in a-BN (which is in contrast to graphite). However, it was concluded that a-BN is an indirect gap insulator, which is in contradiction with previous results for details, see [7]. First-order perturbation theory and the concept of transfer ability have been used to explain degenerate lifting in the two- and three-dimensional electronic ji-band structures of a-BN (and graphite) in a simple orbital context. This leads to band diagrams that correspond qualitatively to those obtained by the various calculational methods [8]. 

Energy Positions of the Peaks (in eV) Recorded in the EELS Spectrum of a-BN [22]. Standard deviation 1.0 eV for all peaks. 

If the spectrometer has a large acceptance angle, a and ji contributions are mixed and the spectrum represents the total DOS (density of states) of the unoccupied states (including a and jr MOs) [22]. There is some doubt whether the exact absolute position and intensity distribution of the first three peaks (a, b, c in Table 4/5) have to be attributed to core-exciton features or to the local density of states effect [22]. Based on an intensity analysis of boron and 

Reflectance spectra of a-BN in the vacuum UV have been recorded between 5 and 25 eV using synchrotron radiation there are peaks at 6.2,7.0, about 10, and 16 eV [35]. Assignments were made according to [36] (see Boron Compounds 1st Suppl. Vol. 2, 1980, p. 28). 

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