Electronic structure of single-crystalline thermoelectric Bi2-xPbxSr2Co2Oy (x=0,0.6) from photoemission and x-ray absorption
- Authors
- Kang, JS; Han, SW; Fujii, T; Terasaki, I; Lee, SS; Kim, G; Olson, CG; Lee, HG; Kim, JY; Min, BI
- Issue Date
- Nov-2006
- Publisher
- AMER PHYSICAL SOC
- Citation
- PHYSICAL REVIEW B, v.74, no.20, pp 809 - 814
- Pages
- 6
- Journal Title
- PHYSICAL REVIEW B
- Volume
- 74
- Number
- 20
- Start Page
- 809
- End Page
- 814
- URI
- https://scholarworks.sookmyung.ac.kr/handle/2020.sw.sookmyung/148531
- DOI
- 10.1103/PhysRevB.74.205116
- ISSN
- 1098-0121
- Abstract
- The electronic structures of Bi2-xPbxSr2Co2Oy (x=0,0.6) thermoelectric single crystals have been investigated by employing photoemission spectroscopy (PES) and polarization-dependent soft x-ray absorption spectroscopy. Co ions are found to be in the Co3+-Co4+ mixed-valent states with the low-spin configuration. The valence-band PES study reveals that the Co 3d states are located at the top of the valence bands, corresponding to the occupied electron configuration of e(g)(pi 4)a(1g)(1+x) (x < 1). Both the topmost occupied states and the lowest unoccupied states have the primarily out-of-plane Co a(1g) character, suggesting that carriers have the Co a(1g) hole character. Angle resolved photoemission spectroscopy measurements show that the lowest binding-energy states are shifted toward E-F with increasing x in Bi2-xPbxSr2Co2Oy, indicating that the carrier states are shifted toward E-F. This study suggests that the thermoelectric property of Bi2-xPbxSr2Co2Oy is improved for x > 0 mainly by the reduced resistivity.
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