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Stress induced monoclinic phase in epitaxial BaTiO3 I. B. Misirlioglu and S. P. Alpaya
 

Summary: Stress induced monoclinic phase in epitaxial BaTiO3
on MgO
I. B. Misirlioglu and S. P. Alpaya
Department of Materials Science and Engineering, University of Connecticut, Storrs, Connecticut 06269
and Institute of Materials Science, University of Connecticut, Storrs, Connecticut 06269
Feizhou Heb
and B. O. Wells
Department of Physics, University of Connecticut, Storrs, Connecticut 06269
Received 7 June 2005; accepted 22 March 2006; published online 30 May 2006
We present a detailed strain analysis of epitaxial ferroelectric films taking into account multiple
sources of strain, including the lattice mismatch between the film and the substrate, thermal strains
due to differences in the thermal expansion coefficients of the film and the substrate, and relaxation
by the formation of interfacial dislocations. The lattice parameters of the film are calculated using
a thermodynamic formalism coupled with the strain analysis. The theoretical model shows
that epitaxial 001 BaTiO3 films on 001 MgO are expected to display successive phase
transformations with decreasing temperatures that are different than the bulk. This is verified
experimentally for 50 nm thick 001 BaTiO3 films grown on 001 MgO substrates at 720 C using
pulsed laser deposition. A synchrotron x-ray diffraction study displays two slope changes in the
temperature dependence of the out-of-plane lattice constant. This indicates that two phase
transformations exist in the film as a function of temperature with transition temperatures and lattice

  

Source: Alpay, S. Pamir - Department of Materials Science and Engineering, University of Connecticut

 

Collections: Materials Science