|일시||June 22 (Fri.), 04:00 PM|
|연사||Dr. Daniel Sando|
Univ. of New South Wales, Sydney
Multiferroics – materials with coexisting ferroic orders such as ferroelectricity and (anti)-ferromagnetism – are presently under intense study by virtue of their promise in next-generation data storage devices. Bismuth ferrite (BiFeO3– BFO) is one of the very few that orders above room temperature. In the bulk, BFO is rhombohedral (R), and in thin films  its properties are sensitive to strain [2,3]. The discovery of the epitaxially-stabilized “super tetragonal phase” of BFO (T-BFO)  incited a flurry of research activity focused on understanding the phase transition and its possible functionalities . T-BFO is also multiferroic, with large ferroelectric polarization and antiferromagnetic order , and the strain relaxation-induced T/R phase mixtures and their exceptional piezoelectric responses  continue to intrigue and motivate researchers. A particularly important characteristic of this phase mixture is the interconversion between the R,T phases with an applied electric field . Since the oxygen configuration of the R and T polymorphs is different , the electronic, magnetic, and optical properties can thus be dynamically modulated. An additional rather crucial (and thus far underexplored) aspect of mixed R/T BFO is the role of chemistryin the formation of the metastable T-phase. Since T-BFO is typically fabricated by pulsed laser deposition, growth parameters can be used as a strong handle to tailor film properties and functionalities.
Here I will describe our work on understanding the influence of strain and growth conditions on the optical, magnetic, and ferroelectric properties of BFO films. I will also show that by precisely controlling fabrication conditions, the formation of the mixed R/T phases in BFO films can be completely suppressed for thicknesses above 70 nm. Such an intriguing result is useful for applications where thicker pure T-BFO films are needed, such as for measuring the expected giant polarization, or for precisely controlling the proportions of the various phases. Finally, through analysis of a large set of epitaxial films, it will be shown that the optical band gap of BFO is rather insensitive to a host of growth and processing parameters . Combined with the numerous other functionalities of this material, one can envisage multifunctional devices, for example, that harvest mechanical and solar energy, or to enhance magnetoelectric coupling at these multiferroic phase boundaries.
 Sando et al., J. Phys: Condens. Matt. 26, 473201 (2014).
 Infante et al., PRL 105, 057601 (2010).
 Sando et al., Nat. Mater. 12, 641 (2013).
 Bea et al., PRL 102, 217603 (2009).
 Sando et al., Appl. Phys. Rev. 3, 011106 (2016).
 Zeches et al., Science 326, 977 (2009).
 Sando et al., Adv. Opt Mater. 6, 1700836 (2018).
Department of Physics, KAIST
|공지||2019/09/18 - 12/5||Seminar Room #1323||Prof. David Schuster and etc.||Fall 2019: Physics Seminar Serises|
|공지||2019/09/02 - 12/09||Seminar Room 1501||이호성 박사 (한국표준과학연구원) and etc.||Fall 2019: Physics Colloquium|
|298||Jul. 28 (Thu.) 4PM||#1323(E6-2. 1st fl.)||Prof. Johannes Pollanen, Jerry Cowen Chair of Experimental Physics at Michigan State University||Low Dimensional Electrons: On the Road to Hybrid Quantum Systems|
|297||Jul. 08 (Fri.) 2PM||#1323(E6-2. 1st fl.)||Dr. Junhyun Lee, Harvard University||Electronic quasiparticles in the quantum dimer model|
|296||Jul. 07 (Thu.) 2PM||#1323(E6-2. 1st fl.)||Dr. Eun Ah Kim, CORNELL UNIV.||Let there be topological superconductors|
|295||Jul. 08 (Fri.) 11:00 AM||#1323(E6-2. 1st fl.)||Dr. Michael Lawler(Binghampton Univ. / Cornell Univ.)||Isostatic magnetism|
|294||Apr. 19(Tue.), 2PM||#1323(E6-2. 1st fl.)||Prof. Mark Koepke, Department of Physics and Astronomy, West Virginia University, USA||Nonlocal collisional electron transport in partially ionized plasma generation, structure, and stability|
|293||February 20 (Thu), 4:00 PM||#1323, E6-2||Seunghyun Khim||Unconventional superconductivity in the locally non-centrosymmetric heavy-fermion CeRh2As2|
|292||January 17 (Fri), 4:00 PM||#1323, E6-2||Hiroki Ikegami||Symmetry Breaking and Topology in Superfluid 3He|
|291||December 18 (Tue.), 4:00 PM||#1323, E6-2||Prof. Shin-ichi Uchida||Road to Higher Tc Superconductivity|
|290||December 13 (Fri.), 1:30-4:30 PM||#1323, E6-2||Biophysics Mini-symposium at KAIST|
|289||December 5 (Thu.), 16:00 PM||#1323, E6-2||Prof. Soon-Hong Kwon||Subwavelenth Photonic Devices: From Single Photon Sources to Solar Cell|
|288||December 3 (Tue.), 4:00 PM||#1323, E6-2||Dr. Jong Mok Ok||Toward Quantum Materials with Correlated Oxides|
|287||November 28 (Thu.), 16:00 PM||#1323, E6-2||Prof. Kyung Taec Kim||Generation of coherent EUV emissions using ultrashort laser pulses|
|286||November 14 (Thu.), 16:00 PM||#1323, E6-2||Prof. Ji-Hun Kang||Semi-classical model of polariton propagation|
|285||November 7 (Thu.), 16:00 PM||#1323, E6-2||Prof. Je-Hyung Kim||Integrated quantum photonics with solid-state quantum emitters|
|284||November 5 (Tue.), 4:00 PM||#1323, E6-2||Dr. Shik Shin||Study on nanomaterials by the development of ultrahigh resolution laser-photoelectron microscopy (PEEM)|
|283||October 29 (Tue.), 14:30 PM||#1323, E6-2||Prof. Jörg Wrachtrup||Quantum sensing|
|282||Oct. 25 (Fri), 15:00 ~||#1323, E6-2||Daesu Lee,Junwoo Son,MyungJoon Han ,Siheon Ryee,Eun-Gook Moon||Physics Seminar|
|281||October 17 (Thu.), 16:00 PM||#1323, E6-2||Prof. Namkyoo Park||Top down manipulation of Waves : From Metamaterials, Correlated Disorder, Quantum Analogy, to Digital Processing|
|280||October 15 (Tue.), 16:00 PM||#1323, E6-2||Prof. Pilkyung Moon||Moiré superlattices and graphene quasicrystal|
|279||September 26 (Thu.), 16:00 PM||#1323, E6-2||Han Seb Moon||Entanglement Swapping with Autonomous Polarization-Entangled Photon-Pairs from Warm Atomic Ensemble|