Soft x-ray photoelectron spectroscopy study of type-I clathrates

Extensive soft x-ray photoelectron spectroscopy studies are performed on Ba 8 Ga 16 Ge 30 (BGG) and Sr 8 Ga 16 Ge 30 (SGG) single crystals ranging from Fermi to core levels, at a high-energy facility. Valence band x-ray photoelectron spectroscopy (XPS) experiments with theoretical calculations revea...

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Bibliographic Details
Published in:Science and technology of advanced materials 2008-12, Vol.9 (4), p.044207-044207
Main Authors: Tang, Jun, Li, Zhaofei, Ju, Jing, Kumashiro, Ryotaro, A. Avila, Marcos, Suekuni, Kouichirou, Takabatake, Toshiro, Guo, FangZhun, Kobayashi, Keisuke, Akai, Koji, Tanigaki, Katsumi
Format: Article
Language:English
Subjects:
core level
Focus Papers
synchrotron radiation
thermoelectric
valence band
x-ray photoelectron spectroscopy
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Summary:Extensive soft x-ray photoelectron spectroscopy studies are performed on Ba 8 Ga 16 Ge 30 (BGG) and Sr 8 Ga 16 Ge 30 (SGG) single crystals ranging from Fermi to core levels, at a high-energy facility. Valence band x-ray photoelectron spectroscopy (XPS) experiments with theoretical calculations revealed that the valence band is mainly constructed by the Ge/Ga 4s and 4p wave functions with little contribution of the Ba/Sr atomic orbitals. Surprisingly, unexpected features evidencing the different shift for the 2a- and 6d- sites between Ba 4d and Sr 3d are observed. The detailed analyses including theoretical support by first-principles band-structure calculations lead to the conclusion that the component distributions of the larger tetrakaidecahedral cage are different depending on the endohedral atoms, which contrasts with the past consensus that BGG and SGG have the same framework structure. This may give thorough reconsiderations on earlier interpretations of experimental data.
ISSN:1468-6996
1878-5514
DOI:10.1088/1468-6996/9/4/044207