To investigate the electronic structure of TiNiSn-based thermoelectric materials, we systematically synthesized samples, Ti1−x Ni1+x Sn (−0.05 ≤ x ≤ 0.05), and performed soft-x-ray photoelectron spectroscopy (XPS) measurements. A peak with a binding energy of about 0.3 eV, not expected from the perfect crystal, was observed in the XPS spectrum, and its intensity became weaker with decreasing x. This peak indicates that defects exist in the x = 0 sample and are reduced with decreasing x. First-principles calculations using several defect models led to the conclusion that interstitial Ni defects in the half-Heusler structure consistently explain the experimental observations, including the XPS spectra and changes in lattice constants.
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Acknowledgements
Synchrotron radiation experiments (Proposal No. 2007A3876) were performed at the BL23SU of JAEA at SPring-8 with approval of nanotechnology network project supported by the Ministry of Education, Culture, Sports, Science, and Technology.
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Hazama, H., Asahi, R., Matsubara, M. et al. Study of Electronic Structure and Defect Formation in Ti1−x Ni1+x Sn Half-Heusler Alloys. J. Electron. Mater. 39, 1549–1553 (2010). https://doi.org/10.1007/s11664-010-1283-4
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DOI: https://doi.org/10.1007/s11664-010-1283-4