2006 Fiscal Year Final Research Report Summary
TlInSe_2 with a nano-modulated structure as a thermoelectric material with a high efficiency _
| Project/Area Number |
17560290
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Electronic materials/Electric materials
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| Research Institution | Osaka Prefecture University |
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Principal Investigator |
WAKITA Kazuki Osaka Prefecture University, Graduate Schodof Engineering, Associate Professor, 工学研究科, 助教授 (80201151)
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| Co-Investigator(Kenkyū-buntansha) |
ASHIDA Atushi Osaka Prefecture University, GraduateSchoolof Engineering, Assistant Professor, 工学研究科, 講師 (60231908)
SHIM Yonggu Osaka Prefecture University, GraduateSchcolof Engineering, Instructor., 工学研究科, 助手 (20336803)
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| Project Period (FY) |
2005 – 2006
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| Keywords | TlInSe_2 / incommensurate phase / Seebeck coeeficient / thermoelectric conversion / Photoluminescence / current-voltage characteristics / ellipsometry / angle-resolved photoemission |
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| Research Abstract |
It is found that some TlInSe_2 samples indicate ferroelectricity. We observed memory effects of current-voltage characteristics. The phenomena are supposed to be the memory effects in an incommensurate phase which is often observed on other thallic compounds.
Next, Photoluminescence (PL) and PL excitation spectra of TlInSe_2 crystals have been investigated. The observed board PL spectra are overlapped by two peaks centered at 1.05 and 0.95 eV. Both separated peaks are considered to be attributed to free-to-bound transition according to excitation intensity dependence of PL spectra. An activation energy of these peaks have also been estimated to evaluate donor or acceptor level associated with the emissions. Furthermore, we have observed PL excitation spectra with exciton-like peaks at 1.17 and 1.23 eV.
The optical absorption of TlInSe_2 has been examined and the structure changes of the spectra were observed in the range of temperature between 60 and 150℃. From the spectra, the compound is found to has an indirect band gap and to change phonon energy associated with the transition in the temperature range. The decrease of phonon energy is attributed to the folding energy band due to a superlattice in the commensurate phase.
Furthermore, TlInSe_2 crystals have been investigated by mean of angle-resolved photoemission spectroscopy. The obtained energy bands favorably agree with the calculated band structure and show quite noticeable dispersion in the direction normal to chains. A rigid shift toward lower binding energies, splitting and the formation of the mini-gap-like structures are clearly observed in the experimental electric bands with the temperature, and causing the record-breaking values of Seebeck coefficient.
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Research Products
(14 results)
