Dynamic Conductivity of Ferroelectric Domain Walls in BiFeO3

Peter Maksymovych,1 Jan Seidel,2-3 Ying Hao Chu,4 Pingping Wu,5 Arthur P. Baddorf,1 Long-Qing Chen,5 Sergei V. Kalinin,1 and Ramamoorthy Ramesh2-3

1 Center for Nanophase Materials Science, Oak Ridge National Laboratory
2 Lawrence Berkeley National Laboratory
3 University of California, Berkeley
4 National Chiao Tung University, Taiwan
5 Pennsylvania State University

Two years ago, electrical conductivity was discovered in domain walls in multiferroic BiFeO3, only 2-3 nm wide and distinct from the surrounding insulating material.1 Conductivity was completely unexpected since domain walls present only a subtle change in the symmetry of the lattice. The origin of the domain wall conductance has remained controversial, with several competing hypotheses including vacancy aggregation3 and local band-gap reduction due to a static distortion.1,4 By combining conductive and piezoresponse force microscopies to characterize, respectively, the nanoscale electron transport and polarization dynamics at the domain walls, we have revealed for the first time that domain walls in BiFeO3 are not rigid conductors, as considered before, but are in fact intrinsically dynamic.

Memristive-like hysteresis in the ferroelectric domain wall conductance. This behavior is measured locally using scanning probes and is isolated at ferroelectric domain walls (inset).

Significance By showing that the conductivity is dynamic and not static, our work points to a very different origin of conductivity than was previously surmised. In particular, it is not the as-grown structure of the wall that is conducting, but rather the distorted (most likely bent, twisted or bowed) domain wall that is at the heart of local conductivity.

This work was published online in Nano Letters 2011. Experiments were performed at the Center for Nanophase Materials Sciences, which is sponsored at the Oak Ridge National Laboratory by the Office of Basic Energy Sciences, U.S. Department of Energy. Work at Berkeley is supported by SRC-NRI-WINS and the Office of Basic Energy Sciences, Materials Sciences Division of the U.S. Department of Energy under contract DE-AC02-05CH1123. J.S. was supported by the Alexander von Humboldt Foundation.

Dynamic Conductivity of Ferroelectric Domain Walls in BiFeO3

P. Maksymovych, J. Seidel, Y. H. Chu, P. Wu, A. P. Baddorf, L.-Q. Chen, S. V. Kalinin, R. Ramesh, “Dynamic Conductivity at Ferroelectric Domain Walls,” Nano Letters, published online 12 April 2011, DOI: 10.1021/nl104363x.


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