Raman Spectroscopy of Strained Epitaxial Bismuth Ferrite Films
Bismuth ferrite (BiFeO3) is a multiferroic material. Multiferroics have both ferroelectric and ferromagnetic properties. This is a highly desirable combination, because it allows for a new generation of electronic (such as memory) devices to be created In this work, we applied Raman spectroscopy to study strained thin films of BiFeO3 grown by molecular beam epitaxy and pulsed laser deposition on different substrates including YAIO3, LaAIO3, NdGaO3, SrTiO3, and ReScO3 (Re = Pr, Nd, Sm, Gd, Tb, Dy) . Raman[b][c] Spectroscopy is the technique of using lasers of a known wavelength to probe the crystal lattice vibrations of a sample. (phonons). Phonon frequencies and their activity in Raman spectra reflect the structure/crystallographic phase state of a material. Our experiments were carried out using ultraviolet lasers of wavelength 325nm in order to reduce the substrate contribution to Raman spectra. The samples were set in a cryostat for low temperature measurements and a heat stage for high temperature measurements. Variable temperature Raman spectroscopy data measured over a broad range of temperatures yield information about different ferroelectric phases of the films depending on temperature and strain.