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Tuning the Tunability in Epitaxial Barium Strontium Titanate Film via Internal Stresses

Published online by Cambridge University Press:  11 February 2011

Z.-G. Ban  and
S. P. Alpay
Z.-G. Ban
Affiliation:
Department of Metallurgy and Materials Engineering and Institute of Materials Science, University of Connecticut, Storrs, CT 06269
S. P. Alpay
Affiliation:
Department of Metallurgy and Materials Engineering and Institute of Materials Science, University of Connecticut, Storrs, CT 06269
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Abstract

The tunability of epitaxial barium strontium titanate films is analyzed theoretically for the first time using a modified phenomenological Landau-Devonshire approach taking into account the formation of unusual ferroelectric phases that cannot form in bulk and single-crystal ceramics. It is shown that enhanced tunability can be achieved by adjusting the misfit strain especially in the vicinity of a structural phase transformation. The internal stresses in epitaxial films as characterized by the misfit strain can be controlled by changing the substrate material and/or varying the film thickness. The latter is due to the possibility of stress relaxation by formation of misfit dislocations that relieve epitaxial stresses at film growth temperature. Based on the thermodynamic model, we provide quantitative estimations of tunability of (001) Ba0.5Sr0.5TiO3 films on (001) LaAlO3 (LAO) and SrTiO3 (STO) as a function of film thickness. The analysis indicates that films on STO substrates should be as thick as possible in order to achieve optimum tunability. To obtain maximum tunability on LAO substrates, the thickness of films should be as close as possible to a critical film thickness (∼120 nm).

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 748: Symposium U – Ferroelectric Thin Films XI , 2002 , U16.3
Copyright
Copyright © Materials Research Society 2003

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References

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