|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|
|249||Nov. 24(Thu) 4p.m.||#1323(E6-2. 1st fl.)||Dr. Jai-Min Choi, Chonbuk National Univiersity||Harmonic oscillator physics with single atoms in a state-selective optical potential|
|248||Nov. 29(Tue) 4p.m.||#1323(E6-2. 1st fl.)||Dr. SungBin Lee, KAIST||Symmetry Protected Kondo Metals and Their Phase Transitions|
|247||Dec. 8(Thu) 4p.m.||#1323(E6-2. 1st fl.)||Dr. Jinhyoung Lee, Hanyang University||Dynamical Resonance between Two Optical Cavities via Optomechanical Oscillator|
|246||Dec. 9(Fri), 1:30 p.m.||#1323(E6-2. 1st fl.)||Dr. Jae Yoon Cho, POSTECH||Entanglement area law in strongly-correlated systems|
|245||Feb. 1 (Wed.), 2p.m.||#1323(E6-2. 1st fl.)||Dr. Michihisa Yamamoto, Department of Applied Physics, The University of Tokyo||Quantum electron optics using flying electrons|
|244||October 18 (Thu.), 16:00 PM||#1323, E6-2||Prof. Jongseok Lee||Applications of nonlinear optics for condensed matter researches|
|243||October 4 (Thu.), 16:00 PM||#1323, E6-2||Prof. Soo Jin Kim||Engineering light absorption in an ultrathin semiconductor metafilm|
|242||October 11 (Thu.), 16:00 PM||#1323, E6-2||Prof. Joung-Real Ahn||Dirac electrons in a graphene quasicrystal|
|241||October 15 (Mon.), 16:00 PM||#1323, E6-2||Dr. Yongjoo Baek||Universal properties of macroscopic current-carrying systems|
|240||October 16 (Tue.), 10:00 AM||#1323, E6-2||Dr. Won-Ki Cho||Capturing protein cluster dynamics and gene expression output in live cells|
|239||October 18 (Thu.), 10:00 AM||#1323, E6-2||Dr. Duyoung Min||Understanding membrane protein folding using single-molecule force techniques|
|238||October 19 (Fri.), 10:00 AM||#1323, E6-2||Dr. Jongsoo Yoo||Energy conversion processes during magnetic reconnection in a laboratory plasma|
|237||September 5 (Wed.), 16:00 PM||#1323, E6-2||Dr. Dirk Wulferding||Shining a light on fractional excitations|
|236||September 20 (Thu.), 16:00||#1323, E6-2||Prof. Joo-Hiuk Son||Toward Cancer Treatment Using Terahertz Radiation: Demethylation of Cancer DNA|
|235||June 27 (Wed.), 13:30 PM||#1323, E6-2||Dr. Jung Sik Park||Magnetic reversal of artificial spin ice|
|234||May 9 (Wed.), 04:00 PM||#1323, E6-2||Prof. Jong-Soo Rhyee||Recent advances in thermoelectric bulk composites|
|233||May 29 (Tue.), 04:00 PM||#1323, E6-2||Prof. Jae-Won Jang||Investigation on metal nanostructure/semiconductor junction and its applications|
|232||May 311 (Thu.), 04:00 PM||#1323, E6-2||Prof. Teun-Teun Kim||Dynamic control of optical properties with gated-graphene metamaterials|
|»||June 22 (Fri.), 04:00 PM||#1323, E6-2||Dr. Daniel Sando||Tuning functional properties of BiFeO3 films using strain and growth chemistry|