|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|
|261||October 16 (Wed), 4:00pm||#1323 (E6-2, 1st fl.)||Dr. Jaewon Song||Emergent black holes and monopoles from quantum fields|
|260||October 16 (Tue.), 10:00 AM||#1323, E6-2||Dr. Won-Ki Cho||Capturing protein cluster dynamics and gene expression output in live cells|
|259||October 15 (Tue.), 16:00 PM||#1323, E6-2||Prof. Pilkyung Moon||Moiré superlattices and graphene quasicrystal|
|258||October 15 (Mon.), 16:00 PM||#1323, E6-2||Dr. Yongjoo Baek||Universal properties of macroscopic current-carrying systems|
|257||October 11 (Thu.), 16:00 PM||#1323, E6-2||Prof. Joung-Real Ahn||Dirac electrons in a graphene quasicrystal|
|256||Oct. 27th(Thu) 4PM||#1323(E6-2)||Dr. 이 강 희, KAIST, Mechnical Engineering||Terahertz Metal Optics|
|255||Oct. 25 (Fri), 15:00 ~||#1323, E6-2||Daesu Lee,Junwoo Son,MyungJoon Han ,Siheon Ryee,Eun-Gook Moon||Physics Seminar|
|254||Oct. 18 (Tue.), 3PM||E6-2. 1st fl. #1323||Dr. JunHo Suh, Korea Research Institute of Standards and Science||“Hybrid quantum systems with mechanical oscillators”|
|253||Oct. 18 (Tue.), 1:30 PM||1st fl. #1323(E6-2)||Dr. Chan-Ho Yang, Department of Physics, KAIST||"Visualization of oxygen vacancy in motion and the interplay with electronic conduction"|
|252||Oct. 17th (Mon) 11:00 AM||#1323,(E6-2, 1st fl.)||Nguyen Quang Liem, Institute of Materials Science, VAST, Viettnam||IMS and examples of the studies on optoelectronic materials|
|251||Oct. 12 (Fri.), 04:00 PM||E6-2. 1st fl. #1323||Dr. HyungWoo Lee||Direct observation of a two-dimensional hole gas at oxide interfaces|
|250||Oct. 12 (Fri.), 02:30 PM||E6-2. 1st fl. #1323||Dr. Daniel Kyungdeock Park||Quantum Advantage in Learning Parity with Noise|
|249||Oct. 10(Tue) 4PM||E6-2 #1323||김성웅 교수 (성균관대학교 에너지과학과)||Discovery of New 2D Materials with Diverse Physical Properties|
|248||Oct. 07 (Fri), 4:00 PM||E6-2. #1323(1st fl.)||Dr. Choong Hyun Kim,IBS-CCES, Seoul National University||“Tilt engineering of 4d and 5d transition metal oxides?”|
|247||Oct. 07 (Fri), 1:30 PM||E6-2. #1323(1st fl.)||Dr. Suk Bum Chung, IBS-CCES , Seoul National University||“Symmetry and topology in transition metal dichalcogenide?”|
|246||November 8 (Thu.), 16:00 PM||#1323, E6-2||이종완 박사||Conformality lost|
|245||November 7 (Thu.), 16:00 PM||#1323, E6-2||Prof. Je-Hyung Kim||Integrated quantum photonics with solid-state quantum emitters|
|244||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)|
|243||November 29 (Thu.), 16:00 PM||#1323, E6-2||Dr. Kee suk Hong||양자 칸델라 실현을 위한 단일 광자 발생장치 개발|
|242||November 28 (Thu.), 16:00 PM||#1323, E6-2||Prof. Kyung Taec Kim||Generation of coherent EUV emissions using ultrashort laser pulses|