Piezoelectric Response and Polarization-Dependent Conductivity of Grain Boundaries in BiFeO3 Thin Films
D.O. Alikin a, Y. Fomichov b, S.P. Reis c d, A.S. Abramov a, D.S. Chezganov a, V.Ya. Shur a, E. Eliseev e, A. Morozovska f, E.B. Araujo d, A.L. Kholkin a b
a Ural Federal University, School of Natural Sciences and Mathematics, Ekaterinburg, Russia, Russian Federation
b Faculty of Mathematics and Physics, Charles University in Prague, Prague 8, 180 00, Czech Republic
c Department of Chemistry and Physics, São Paulo State University, Ilha Solteira - SP, Brazil
d Federal Institute of Education, Science and Technology of São Paulo, 15503-110 Votuporanga, Brazil
e Institute for Problems of Materials Science, National Academy of Sciences of Ukraine, 03142 Kyiv, Ukraine
f Institute of Physics, National Academy of Sciences of Ukraine, 03028 Kyiv, Ukraine 7Department of Physics & CICECO—Aveiro Institute of Materials, University of Aveiro, 3810–193, Aveiro
nanoGe Fall Meeting
Proceedings of nanoGe Fall Meeting19 (NGFM19)
#MapNan19. Mapping Nanoscale Functionality with Scanning Probe Microscopy
Berlin, Germany, 2019 November 3rd - 8th
Organizer: Stefan Weber
Oral, D.O. Alikin, presentation 348
Publication date: 16th July 2019

Many efforts have been devoted so far to achieve the control of interfaces in ferroelectric materials based on their polarization. These efforts resulted in the discovery of a variety of different phenomena such as polarization-dependent tunneling effect, resistive switching, symmetry breaking, etc. [1,2] In particular, domain wall conductivity [3], formation of topological defects [4], phase boundaries[5] and ferroelectric-insulator interfaces [6] have been studied. Charge transport across the interfaces in complex oxides attracts a lot of attention because it allows creating novel functionalities useful for device applications. In particular, it has been observed that movable domain walls in epitaxial BiFeO3 films possess enhanced conductivity that can be used for read out in ferroelectric-based memories [3]. In this work, the relation between the piezoelectric response, polarization and conductivity in sol-gel BiFeO3 films with special emphasis on grain boundaries (GBs) as natural interfaces in polycrystalline ferroelectrics is investigated. The grains exhibit self-organized domain structure in these films, so that the “domain clusters” consisting of several grains with aligned polarization directions are formed. Surprisingly, GBs between these clusters (with antiparallel polarization direction) have significantly higher electrical conductivity in comparison to “inter-cluster” GBs, in which the conductivity was even smaller than in the bulk. As such, polarization-dependent conductivity of the GBs was observed for the first time in ferroelectric thin films. The results are rationalized by thermodynamic modelling combined with finite element simulations of the charge and stress accumulation at the GBs giving major contribution to conductivity.

The existence of low and highly conductive GBs may have an important impact on many macroscopic properties, e.g. dielectric permittivity and leakage current. It becomes even more important for nanosized-grain ceramics, where the influence of multiple GBs is dominant. Conductive GBs may have as well significant effect on the domain wall motion and polarization reversal in polycrystalline materials. The observed polarization-dependent conductivity of GBs in ferroelectrics opens up a new avenue for exploiting these materials in electronic devices.

 

 

The research was made possible by Russian Science Foundation (Grant 19-72-10076). The equipment of the Ural Center for Shared Use “Modern nanotechnology” UrFU was used.

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