Raman Spectroscopy for Characterization of Crystalline Phases and Phase Transformations in Multifunctional Oxide Nanostructures

Dmitri A. Tenne
Department of Physics
Boise State University

Complex oxides are a vast class of materials that have a wide variety of functional properties. Among these functionalities, ferroelectricity and ferromagnetism have been intensively studied over the past few decades. Ferroelectrics are a class of materials possessing a spontaneous electric polarization, which arises from the ordering of electric dipoles and can be switched between crystallographically defined directions by applying electric field. In recent years, the advances of epitaxial oxide thin film deposition have rapidly moved the science and technology of ferroelectrics and multiferroics (materials that exhibit both ferroelectric and magnetic ordering) towards thin films and multilayer structures at the nanometer scale. Nanoscale ferroelectrics and multiferroics are currently a central topic of research in the field of ferroelectricity. Of major importance for understanding the behavior of ferroelectrics is the crystal lattice dynamics, which is related to their fundamental properties. Raman spectroscopy is one of the most powerful analytical techniques for studying the lattice vibrations in solids. It is also a technique capable of distinguishing crystalline polymorphs and detecting phase transformations between different crystal structures in bulk and nanoscale solids. Applications of Raman spectroscopy to studies of several oxide material systems will be discussed, including ferroelectric superlattices BaTiO3/SrTiO3, strained thin films of ferroelectric BaTiO3,  multiferroic BiFeO3 and photocatalytic BiVO4.