Jpn. J. Appl. Phys. 41 (2002) pp. 6628-6632  |Next Article|  |Table of Contents|
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Influence of Strains and Defects on Ferroelectric and Dielectric Properties of Thin-Film Barium–Strontium Titanates

Davor Balzar^1,2,, Padmanabhan A. Ramakrishnan³, Priscila Spagnol⁴, Sugantha Mani^1,2, Allen M. Hermann³ and Mohammad A. Matin⁵

(Received May 29, 2002; accepted for publication August 8, 2002)

Pristine, W and Mn 1% doped Ba_0.6Sr_0.4TiO₃ epitaxial thin films grown on the LaAlO₃ substrate were deposited by pulsed laser deposition (PLD). Dielectric and ferroelectric properties were determined by the capacitance measurements and X-ray diffraction was used to determine both residual elastic strains and defect-related inhomogeneous strains by analyzing diffraction line shifts and line broadening, respectively. We found that both elastic and inhomogeneous strains are affected by doping. This strain correlates with the change in Curie-Weiss temperature and can qualitatively explain changes in dielectric loss. To explain the experimental findings, we model the dielectric and ferroelectric properties of interest in the framework of the Landau-Ginzburg-Devonshire thermodynamic theory. As expected, an elastic-strain contribution due to the epilayer-substrate misfit has an important influence on the free-energy. However, additional terms that correspond to the defect-related inhomogeneous strain had to be introduced to fully explain the measurements.

KEYWORDS: ferroelectric thin films, strain, defects, Curie-Weiss temperature, barium–strontium titanate
URL: http://jjap.ipap.jp/link?JJAP/41/6628/
DOI: 10.1143/JJAP.41.6628

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