|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
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|191||Sep. 02(Fri) 4:00 PM||E6-2(1st fl) #1323||Dr. Yong-Joo Doh, Department of Physics and Photon Science, GIST||Quantum Electrical Transport in Topological Insulator Nanowires|
|190||Jan. 17(Mon) - 21 (Fri), 2-4pm||E6-2 Room 2502||Dr. Donghui Jeong (Penn State University)||Five Lectures on Observational Probes of Dark Energy|
|189||Nov. 12 (Thu.) 4:00 PM||E6-2 1323||김영덕 (Young Duck Kim) 교수||2020 가을학기 광학분야 특별세미나|
|188||Sep. 29th(Thu), 4PM||E6-2 #1323 (1st floor)||Dr. Sangyoon Han, Department of Physics, KAIST||Large-scale Silicon Photonic MEMS Switches|
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|178||2016/03/07-06/13||E6, 1501||Prof. David Helfman(KAIST) 외||Physics Colloquium : 2016 Spring|
|177||2015/09/07-12/01||E6, 1501||문은국 교수(KAIST) 외||Physics Colloquium : 2015 Fall|
|176||2015/03/09-06/08||E6, 1501||최현용교수(연세대) 외12명||Physics Colloquium : 2015 Spring|
|175||2015/09/15-12/08||E6, 1501||박제근 교수(서울대 물리학과) 외12명||Physics Colloquium : 2014 Fall|
|174||2014/03/10-06/09||E6, 1501||신용일교수(서울대)||Physics Colloquium : 2014 Spring|
|173||2013/09/09-12/09||E6, 1501||박혁규교수(부산대) 외||Physics Colloquium : 2013 Fall|