Enhanced Electric Conductivity at Ferroelectric Vortex Cores in BiFeO3
Nina Balke,1 Benjamin Winchester,2 Wei Ren,3 Ying Hao Chu,4,5 Anna N. Morozovska,6 Eugene A. Eliseev,7 Mark Huijben,8 Rama K. Vasudevan,9 Petro Maksymovych,1 Jason Britson,2 Stephen Jesse,1 Igor Kornev,10 Ramamoorthy Ramesh,5 Laurent Bellaiche,3 Long Qing Chen,2 and Sergei V. Kalinin1
1 The Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831
2 Department of Materials Science and Engineering, Pennsylvania State University, University Park, Pennsylvania 16802 (USA)
3 Physics Department and Institute for Nanoscience and Engineering, University of Arkansas, Fayetteville, Arkansas 72701, USA
4 Department of Materials Science and Engineering, National Chiao Tung University, Hsinchu 30010, Taiwan
5 Department of Materials Science and Engineering and Department of Physics, University of California, Berkeley, California 94720
6 Institute for Problems of Materials Science, National Academy of Science of Ukraine, Kiev, Ukraine
7 Institute of Semiconductor Physics, National Academy of Science of Ukraine, Kiev, Ukraine
8 Faculty of Science and Technology, MESA+ Institute for Nanotechnology, University of Twente, 7500 AE, Enschede, The Netherlands
9 School of Materials Science and Engineering, University of New South Wales, Sydney 2052, Australia
10 Laboratoire Structures, Proprietes et Modelisation des Solides, Ecole Centrale Paris, CNRS-UMR8580, Grande Voie des Vignes, 92295 Chatenay-Malabry Cedex, France
We report enhanced electrical conductivity at artificially created ferroelectric vortex cores in BiFeO3 thin films. Controlled motion of a biased SPM tip is used to carefully pattern a lattice of vortex and anti-vortex topological defects, while conduction-AFM (c-AFM) is used to probe the electronic transport at the vortex cores. Through first-principles and phase-field and modeling, it is found that the core can undergo a transformation to a metastable twist structure, extending charged wall segments through the film. The vortex cores are thus determined to be dynamic 1D conductors.
To date, there has been a wealth of theoretical and experimental studies on 2D topological defects, such as conducting domain walls. However, the formation of 1D conducting channels is required for ‘wiring’ in functional devices. Hence, the controlled creation of 1D conducting channels in a ferroelectric material offers a pathway for the design and implementation of integrated oxide electronic devices based on domain patterning.
Experiments were conducted at the Center for Nanophase Materials Sciences, which is sponsored at Oak Ridge National Laboratory by the Office of Basic Energy Sciences, U.S. Department of Energy. Support was provided by the Division of Scientific User Facilities (N.B.) and by the Materials Sciences and Engineering Division (S.V.K.) of the US Department of Energy, Basic Energy Sciences. B.W., J.B. and L.Q.C. are supported by US Department of Energy, Basic Sciences, under Grant No. DE-FG02-07ER46417. L.B. thanks mostly support from the Department of Energy, Office of Basic Energy Sciences, under contract ER-46612. L.B. also thanks the National Science Foundation grants DMR-1066158 and DMR-0701558, and Office of Naval Research grants N00014-11-1-0384, N00014-08-1-0915 and N00014-07-1-0825. Some computations were also made possible thanks to the National Science Foundation grant 0722625 and a challenge grant from the U.S. Department of Defense. Y.H.C. acknowledges the support of the National Science Council, Republic of China, under contract NSC-100-2811-M-009-003. M.H. acknowledges support by the Netherlands Organization for Scientific Research (NWO) through a VENI grant.
“Enhanced Electric Conductivity at Ferroelectric Vortex Cores in BiFeO3,” N. Balke, B. Winchester, W. Ren, Y.-H. Chu, A.N. Morozovska, E.A. Eliseev, M. Huijben, R.K. Vasudevan, P. Maksymovych, J. Britson, S. Jesse, I. Kornev, R. Ramesh, L. Bellaiche, L.-Q. Chen, and S.V. Kalinin, Nature Physics (2011), AOP.