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Structural and Electronic Properties of Carbon‐Doped β‐Rhombohedral Boron
Author(s) -
Werheit H.,
Kuhlmann U.,
Laux M.,
Lundström T.
Publication year - 1993
Publication title -
physica status solidi (b)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.51
H-Index - 109
eISSN - 1521-3951
pISSN - 0370-1972
DOI - 10.1002/pssb.2221790223
Subject(s) - boron , raman spectroscopy , materials science , doping , electron energy loss spectroscopy , phonon , carbon fibers , condensed matter physics , atomic physics , molecular physics , chemistry , nanotechnology , transmission electron microscopy , optics , physics , optoelectronics , organic chemistry , composite number , composite material
Abstract β‐rhombohedral boron doped with carbon up to about 1 at% is investigated by X‐ray diffraction, by optical transmission spectroscopy in the spectral range of the absorption edge and its low energy tail, by I R reflection spectroscopy in the lattice vibration range, and by Raman scattering. The carbon atoms substitute for boron sites in the icosahedra shrinking as a consequence of the increased intraicosahedral bonding force. Hence the lattice constants decrease with increasing carbon content. Within the accuracy of measurement the interband transition energies are not influenced by the carbon content, and the p‐type conductivity remains qualitatively unchanged. Additionally to the series of six ionization energies of B 12 electron trapping levels, which are equidistantly arranged below the conduction band in pure boron, a second series of B 11 C trapping levels develops. The traps are esscntially generated by the interaction between one electron each and up to six pairs (probably triples) of defined phonons. These phonons are quenched as a consequence of the occupation of these traps. In correlation with the new optical results ESR investigations of other authors can now be interpreted. Important details of the electronic structure and its modification by carbon doping are determined. The relevance for other boron‐rich solids with icosahedral structure is discussed.