Probing Nanoscale Ferroelectricity by Ultraviolet Raman Spectroscopy

Department of Physics, Pennsylvania State University, University Park, PA 16802, USA.
Science (Impact Factor: 33.61). 10/2006; 313(5793):1614-6. DOI: 10.1126/science.1130306
Source: PubMed


We demonstrated that ultraviolet Raman spectroscopy is an effective technique to measure the transition temperature (Tc) in ferroelectric ultrathin films and superlattices. We showed that one-unit-cell-thick BaTiO3 layers in BaTiO3/SrTiO3 superlattices are not only ferroelectric (with Tc as high as 250 kelvin) but also polarize the quantum paraelectric SrTiO3 layers adjacent to them. Tc was tuned by approximately 500 kelvin by varying the thicknesses of the BaTiO3 and SrTiO3 layers, revealing the essential roles of electrical and mechanical boundary conditions for nanoscale ferroelectricity.

Download full-text


Available from: Dmitri A Tenne, Sep 29, 2015
1 Follower
24 Reads
  • Source
    • "There has been a great deal of research on the influence of film strain in hetero-epitaxial films due to the film/substrate lattice misfit. The lattice misfit has been used to enhance the Curie temperature of high temperature superconductors1, to alter the Curie temperature of ferromagnetic transition in Colossal Magnetoresistance (CMR) materials2345, and to change the dielectric properties of ferroelectric materials678. In principle, the lattice misfit induced strain energy can be partially or fully released at the interface between the epitaxial film and substrates via formation of edge dislocations that periodically distribute along the interface. "
    [Show abstract] [Hide abstract]
    ABSTRACT: The ability to control the microstructures and physical properties of hetero-epitaxial functional oxide thin films and artificial structures is a long-sought goal in functional materials research. Normally, only the lattice misfit between the film and the substrate is considered to govern the physical properties of the epitaxial films. In fact, the mismatch of film unit cell arrangement and the Surface-Step-Terrace (SST) dimension of the substrate, named as "SST residual matching", is another key factor that significantly influence the properties of the epitaxial film. The nature of strong local strain induced from both lattice mismatch and the SST residual matching on ferroelectric (Ba,Sr)TiO3 and ferromagnetic (La,Ca)MnO3 thin films are systematically investigated and it is demonstrated that this combined effect has a dramatic impact on the physical properties of highly epitaxial oxide thin films. A giant anomalous magnetoresistance effect (~10(10)) was achieved from the as-designed vicinal surfaces.
    Scientific Reports 10/2013; 3:3092. DOI:10.1038/srep03092 · 5.58 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Magnetic tunnel junctions with ferroelectric barriers, often referred to as multiferroic tunnel junctions, have been proposed recently to display new functionalities and new device concepts. One of the notable predictions is that the combination of two charge polarizing states and the parallel and antiparallel magnetic states could make it a four resistance state device. We have recently studied the ferroelectric tunneling using a scanning probe technique and multiferroic tunnel junctions using ferromagnetic La0.7Ca0.3MnO3 and La0.7Sr0.3MnO3 as the electrodes and ferroelectric (Ba, Sr)TiO3 as the barrier in trilayer planner junctions. We show that very thin (Ba, Sr)TiO3 films can sustain ferroelectricity up till room temperature. The multiferroic tunnel junctions show four resistance states as predicted and can operate at room temperatures.
    Frontiers of Physics 08/2012; 7(4). DOI:10.1007/s11467-012-0266-8 · 2.09 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The concept and design of acoustic Bragg mirrors and cavities made of multilayers of piezoelectric oxides with superior acoustic performance and potential applications in electronic and optical terahertz modulators are described. With these applications in mind the authors have grown phonon mirrors consisting of BaTiO3/SrTiO3 superlattices on SrTiO3 substrates by reactive molecular-beam epitaxy and investigated their properties. Characterization of the superlattices by x-ray diffraction and high-resolution transmission electron microscopy reveals high structural quality with nearly atomically abrupt interfaces. The authors have observed folded acoustic phonons at the expected frequencies using uv Raman spectroscopy.
    Applied Physics Letters 01/2007; 90(4):042909-042909-3. DOI:10.1063/1.2432246 · 3.30 Impact Factor
Show more