Modification of Temperature Dependence of Dielectric Properties by Symmetry-Controlled Superlattice Thin Films of BaZrxTi1-xO3

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Symmetry-controlled ferroelectric superlattice thin films of BaZrxTi1-xO3 (BZT) were fabricated by a pulse laser deposition (PLD) technique. To reduce the strain effects, we used 5-layer systems of BZT with $x=0$, 0.25, 0.5, 0.75, and 1; we call these A, B, C, D, and E, respectively. We made two types of superlattice film, namely, ABCDE/ABCDE and ABCDE/EDCBA, where the total concentration of Zr was the same. The former exhibits symmetry breaking as in perovskite structures. In contrast, the latter has symmetry introduced by artificial structures. Superlattices show clear satellite peaks in XRD patterns and the structures are also confirmed by electron microscopy images. ABCDE/ABCDE films have larger relative permittivities than the ABCDE/EDCBA films. This property seems to be the symmetry effects in the superlattice structures. Both films have a weak temperature dependence near room temperature caused by the superlattice effects, which seems to be better for the application of the materials.
2006-05-30