Berlin 2008 – wissenschaftliches Programm
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DS: Fachverband Dünne Schichten
DS 21: High-k Dielectric Materials - Synthesis, Properties, Applications
DS 21.3: Vortrag
Mittwoch, 27. Februar 2008, 15:30–15:45, H 2032
Broadband dielectric response of CaCu3Ti4O12: significant intrinsic properties — •Stephan Krohns1, Christian Kant1, Torsten Rudolf1, Franz Mayr1, Peter Lunkenheimer1, Stefan Ebbinghaus2, and Alois Loidl1 — 1Experimental Physics V, Center for Electronic Correlations and Magnetism, University of Augsburg, 86135 Augsburg, Germany — 2Solid State Chemistry, Universitiy of Augsburg, 86135 Augsburg, Germany
For applications, e.g., in wireless electronics, materials with colossal dielectric constant are in great demand. Since first reports of very large ("colossal") dielectric constants є’ up to the order of 105 in CaCu3Ti4O12 (CCTO), this material is in the focus of scientific and technical interest [1,2]. Not only the understanding of the origin of the most likely extrinsic colossal є’ values is important, but also the clarification of the intrinsic dielectric properties is of high relevance. By combining dielectric and optical methods, we provide dielectric spectra of CCTO covering 15 decades in frequency. Aside of its colossal dielectric constant, CCTO behaves unusual also in other respects. For example, we report an unusual temperature dependence of the low lying phonon modes, revealing a softening that may point to an underlying ferroelectric instability in this material. In addition, information on electronic excitations in CCTO is provided [3].
[1] C.C. Homes et al., Science 293, 673 (2001). [2] S. Krohns et al., Appl. Phys. Lett. 91, 022910 (2007). [3] Ch. Kant et al., arXiv:0709.1065