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Silicon and Germanium Network Polyhedra viewed from Soft X-ray Spectroscopy

Published online by Cambridge University Press:  01 February 2011

Jun Tang ,
Takeshi Rachi ,
Marcos A Avila ,
Toshiro Takabatake ,
FagZhum Guo ,
Keisuke Kobayashi ,
Koji Akai  and
Katsumi Tanigaki
Jun Tang
Affiliation:
tangju@sspns.phys.tohoku.ac.jp, Tohoku University, Graduate of Science, Department of Physics, 6-3 Aoba, Aramaki, Aoba, Sendai, 980-8578, Japan
Takeshi Rachi
Affiliation:
rachi@sspns.phys.tohoku.ac.jp, Tohoku University, Graduate of Science, Department of Physics, 6-3 Aoba, Aramaki, Aoba, Sendai, 980-8578, Japan
Marcos A Avila
Affiliation:
avila@sci.hiroshima-u.ac.jp, Hiroshina University, Dep. Quantum Matter, Kagamiyama 1-3-1, Higashi-Hiroshima, N/A, Japan
Toshiro Takabatake
Affiliation:
takaba@hiroshima-u.ac.jp, Hiroshina University, Dep. Quantum Matter, Kagamiyama 1-3-1, Higashi-Hiroshima, N/A, Japan
FagZhum Guo
Affiliation:
fz-guo@spring8.or.jp, SPring-8, 1-1-1 Mikazuki-machi, Sayo-gun, Hyogo, N/A, Japan
Keisuke Kobayashi
Affiliation:
koba_kei@spring8.or.jp, SPring-8, 1-1-1 Mikazuki-machi, Sayo-gun, Hyogo, N/A, Japan
Koji Akai
Affiliation:
akai@po.cc.yamaguchi-u.ac.jp, Yamaguchi University, Computer Media Center, 2-16-1 Tokiwadai, Ube, 755-8611, Japan
Katsumi Tanigaki
Affiliation:
tanigaki@sspns.phys.tohoku.ac.jp, Tohoku University, Graduate of Science, Department of Physics, 6-3 Aoba, Aramaki, Aob a, Sendai, 980-8578, Japan
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Abstract

The electronic states of Ba8Ga16Ge30 and Sr8Ga16Ge30 are studied by soft x-ray photoelectron spectroscopy (XPS) at a high-energy facility. In Ba8Ga16Ge30, three bands are resolved in the valence band region. Resonance experiments together with theoretical calculations show that the three band structures in the valence band are mainly constructed by the Ge/Ga 4s and 4p wave functions with little contributions of Ba 5s, 5p and 5d. The valence band of Sr8Ga16Ge30 shows a similar feature to that of Ba8Ga16Ge30. It is clearly shown that the atomic orbitals of Ba and Sr make little hybridization with the orbitals made by the framework polyhedra. This provides the understanding of the thermoelectricity in clathrates, and assists the design in high performance thermoelectric materials in this family.

Keywords

thermoelectricityx-ray photoelectron spectroscopy (XPS)electronic structure
Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 1044: Symposium U – Thermoelectric Power Generation , 2007 , 1044-U05-02
Copyright
Copyright © Materials Research Society 2008

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