|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
|159||Sep. 29th(Thu), 4PM||E6-2 #1323 (1st floor)||Dr. Sangyoon Han, Department of Physics, KAIST||Large-scale Silicon Photonic MEMS Switches|
|158||Oct 23 (Fri.), 14:00 PM||E6-2 #1323||Prof. Ivan Savenko (University of Science and Technology & IBS PCS)||Plasmon spectroscopy of low-dimensional superconductors in fluctuating regime|
|157||Oct. 10(Tue) 4PM||E6-2 #1323||김성웅 교수 (성균관대학교 에너지과학과)||Discovery of New 2D Materials with Diverse Physical Properties|
|156||DEC. 26 (Wed), 04:00 PM||E6-1. 3rd fl. #3434||Y. Kim, A. Go, K. Hwang and E.-G. Moon||Informal Workshop on Topology and Correlation|
|155||October 24 (Wed.), 10:30 AM||E6-1, Lecture Room 1501(1F)||Prof. Kerry J. Vahala||Photonic integration of next-generation clocks and Hertz-absolute-accuarcy optical frequenncy synthesizers|
|154||2014/12/22, 2PM||E6, Rm1319||Prof. Changbong Hyeon (KIAS)||Dynamics of molecular motors: Power stroke vs Brownian ratchet|
|153||2016/03/07-06/13||E6, 1501||Prof. David Helfman(KAIST) 외||Physics Colloquium : 2016 Spring|
|152||2015/09/07-12/01||E6, 1501||문은국 교수(KAIST) 외||Physics Colloquium : 2015 Fall|
|151||2009/02/23-05/04||E6, 1501||안종현교수(성균관대) 외||Physics Colloquium : 2009 Spring|
|150||2009/09/07-11/30||E6, 1501||이주영박사(KIAS) 외||Physics Colloquium : 2009 Fall|
|149||2009/10/21, 4PM||E6, 1501||최석봉교수(서울대)||Interdimensional Universality of Dynamic Interfaces|
|148||2010/02/08-05/03||E6, 1501||최인수교수(서울대) 외||Physics Ciolloquium : 2010 Spring|
|147||2011/09/03-12/06||E6, 1501||김용균교수(한양대) 외||Physics Colloquium : 2011 Fall|
|146||2010/09/06-12/06||E6, 1501||조호진기자(조선일보) 외||Physics Colloquium : 2010 Fall|
|145||2010/02/14-05/09||E6, 1501||황철주(주성엔지니어링 사장) 외||Physics Colloquium - 2011 Spring|
|144||2011/05/16, 4PM||E6, 1501||서민교교수(KAIST)||Photonics with surface plasmon polaritons|
|143||2012/02/13-05/14||E6, 1501||Kenji Ohmori (Photo-Molecular Science, IMS)||Physics Colloquium : 2012 Spring|
|142||2012/04/02, 4PM||E6, 1501||Yong Hee Jeong||A new route to ferroelectricity in magnetic spinels: a case of Co2MnO4|
|141||2013/03/11-06/10||E6, 1501||강명수교수(KAIST) 외||Physics Colloquium : 2013 Spring|
|140||2013/09/09-12/09||E6, 1501||박혁규교수(부산대) 외||Physics Colloquium : 2013 Fall|