Interband Transitions, IR-Active Phonons, and Plasma Vibrations of Some Metal Hexaborides
✍ Scribed by H. Werheit; T. Au; R. Schmechel; Yu.B. Paderno; E.S. Konovalova
- Publisher
- Elsevier Science
- Year
- 2000
- Tongue
- English
- Weight
- 175 KB
- Volume
- 154
- Category
- Article
- ISSN
- 0022-4596
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✦ Synopsis
The high IR re6ectivity of monocrystalline metallic metal hexaborides is superimposed by weak phonon spectra. The symmetry selection rules are lifted, probably because of structural defects. From the plasmon+phonon polariton frequencies in metallic LaB 6 compared with those in semiconducting EuB 6 and YbB 6 , the softening and the hardening of speci5c F 1u modes by the free carriers are determined. From the plasma edges of EuB 6 and YbB 6 , some parameters of the electronic transport are derived. The electron concentration increases proportional to the C content, whose donor properties are found to be comparable to those of hydrogen-like impurities. The existence of energy gaps in EuB 6 and YbB 6 proves that these compounds are semiconductors.