Present knowledge of electronic properties and charge transport of icosahedral boron-rich solids

B12 icosahedra or related structure elements determine the different modifications of elementary boron and numerous boron-rich compounds from α-rhombohedral boron with 12 to YB66 type with about 1584 atoms per unit cell. Typical are well-defined high density intrinsic defects: Jahn-Teller distorted...

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Bibliographic Details
Published in:Journal of physics. Conference series 2009-06, Vol.176 (1), p.012019
Main Author: Werheit, Helmut
Format: Article
Language:English
Subjects:
Antisite defects
Boron
Charge transport
Conduction bands
Electron transport
Electronic properties
Hopping conduction
Icosahedrons
Jahn-Teller effect
Physics
Point defects
Unit cell
Valence
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Summary:B12 icosahedra or related structure elements determine the different modifications of elementary boron and numerous boron-rich compounds from α-rhombohedral boron with 12 to YB66 type with about 1584 atoms per unit cell. Typical are well-defined high density intrinsic defects: Jahn-Teller distorted icosahedra, vacancies, incomplete occupancies, statistical occupancies and antisite defects. The correlation between intrinsic point defects and electron deficiencies solves the discrepancy between theoretically predicted metal and experimentally proved semiconducting character. The electron deficiencies generate split-off valence states, which are decisive for the electronic transport, a superposition of band-type and hopping-type conduction. Their share depends on actual conditions like temperature or pre-excitation. The theoretical model of bipolaron hopping is incompatible with numerous experiments. Technical application of the typically p-type icosahedral boron-rich solids requires suitable n-type counterparts; doping and other possibilities are discussed.
ISSN:1742-6596
1742-6588
1742-6596
DOI:10.1088/1742-6596/176/1/012019