Dynamic Response of Epitaxial Ferroelectric Thin Films

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NON-TECHNICAL DESCRIPTION:Ferroelectric thin films have applications in ultrafast optical communication systems and non-volatile semiconductor memories. Future applications of these systems will require an understanding of the polarization switching dynamics in the picosecond time regime. As part of the program an apparatus will be developed to measure the kinetics of domain switching in the picosecond time regime. This work should extend our understanding of phase transformations of materials at ultrafast time scales. The research will involve the training of undergraduate and graduate students in the area of ferroelectric oxide synthesis, ultrafast optical measurements of kinetic processes and model development. The PI and graduate students will be involved in the development of an educational module on material phase transformations and complex phenomena for grades K-12.TECHNICAL DETAILS: The transformation kinetics of domains in epitaxial ferroelectric (FE) thin films of BaTiO3 and KNbO3 will be investigated in the picosecond time regime. Epitaxial FE films will be prepared by metalorganic vapor phase epitaxy and molecular beam epitaxy. The polarization switching kinetics will be determined from the temporal dependence of the electro-optic effect, which depends on the ferroelectric domain volume fraction. The effect of mismatch strain, electric field and temperature on the switching kinetics will be measured and analyzed. The static domain structure will be determined using transmission electron microscopy, near-field scanning optical microscopy and x-ray diffraction. The kinetics will be analyzed with respect to the recently developed dynamic model for multidomain films. The applicability of the universal dielectric response theory to the dynamics of ferroelectric films at high frequencies will be investigated.