Condensed Matter Physics Seminar
Tuning Phase Transitions in Epitaxial Perovskite Films
Department of Physics
University of Connecticut
Perovskites and perovskite-related compounds have many interesting properties, such as high-TC superconductivity, metal-insulator transitions, and colossal magneto-resistivity. Thin films of these materials are important for technology, but the films may have properties quite different from bulk samples. Epitaxial strain due to the lattice mismatch between thin films and substrates is believed to be an important reason. We have studied the cubic to tetragonal phase transition in epitaxial SrTiO3 (STO) films under various biaxial strain conditions using synchrotron X-ray diffraction. The structural phase transitions at about 105 K, as well as the evolution of the lattice parameters, are monitored under various strain conditions. It is found that phase transition temperature is a strong function of strain, with an increase in Tc as much as 50 K. This strain-induced effect can be used to tune the phase ransitions in perovskite thin films. Surprisingly, the lattice constants evolve smoothly through the phase transition, with no indication that a transition occurred. This signals an important change in the nature of the phase transition due to the substrate clamping effect.
Thursday, September 25, 2003
Gant Science Complex
(The seminar is followed by coffee/tea, cookies, and an informal discussions.)