Speaker: X. Q. Pan , University of Michigan
Date & Time: April 21, 2006 - 12:00pm
Location: Serin E385, Physics and Astronomy
Role of Interface on Structure and Properties of Epitaxial Ferroelectric Thin Films
Laboratory for Surface Modification
X. Q. Pan, University of Michigan
12:00 Noon, Serin E385, Physics and Astronomy
This talk is given on the structure-property relationships of interfaces in epitaxial ferroelectric thin films. The effect of lattice mismatch (epitaxial strain), crystal defects, and chemistry at the film/substrate interfaces on the microstructure and properties of different systems (e.g., BaTiO3, SrTiO3, SrRuO3, and Pb(Mg1/3Nb2/3)O3-PbTiO3 (PMN-PT)) will be addressed. The interfacial atomic structure and defects of the films were investigated by high-resolution transmission electron microscopy (HRTEM). The structure and formation mechanisms of misfit dislocations and their significance for the relaxation of epitaxial strain were systematically investigated. Quantitative HRTEM analysis of strained BaTiO3 predicts the enhancement of spontaneous polarization by 200%, which is consistent with the direct measurements of strained BaTiO3 thin films using epitaxial SrRuO3 electrodes. It has also been shown that epitaxial strain can be harnessed to elevate ferroelectric transition temperature (Tc) by hundreds of degrees in both BaTiO3 and SrTiO3 thin films and produce room-temperature ferroelectricity in SrTiO3, a material that normally is not ferroelectric at any temperature.