Hardening of the ferroelectric soft mode in Sr Ti O 3 thin films

We have studied the origin of soft-mode hardening in Sr Ti O 3 thin films using broadband terahertz time-domain spectroscopy. We measured the dielectric dispersions in the terahertz region of as-deposited, O 2 annealed, and high-temperature annealed Sr Ti O 3 thin films deposited on MgO and La 0.3 S...

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Published in:Applied physics letters 2008-09, Vol.93 (13), p.132903-132903-3
Main Authors: Katayama, Ikufumi, Shimosato, Hiroshi, Rana, Dhanvir Singh, Kawayama, Iwao, Tonouchi, Masayoshi, Ashida, Masaaki
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Summary:We have studied the origin of soft-mode hardening in Sr Ti O 3 thin films using broadband terahertz time-domain spectroscopy. We measured the dielectric dispersions in the terahertz region of as-deposited, O 2 annealed, and high-temperature annealed Sr Ti O 3 thin films deposited on MgO and La 0.3 Sr 0.7 Al 0.65 Ta 0.35 O 3 substrates. The results show that the ferroelectric soft mode softens dramatically by the high-temperature annealing. We also measure x-ray diffractions and atomic force microscope images and conclude that the hardening of the ferroelectric soft mode in the thin films is determined by the grain size of each crystalline domain which is enlarged by the high-temperature annealing due to remelting.
ISSN:0003-6951
1077-3118
DOI:10.1063/1.2991442