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Title: Direct observation of room-temperature out-of-plane ferroelectricity and tunneling electroresistance at the two-dimensional limit
Authors: Wang H.
Liu Z.R.
Yoong H.Y.
Paudel T.R.
Xiao J.X. 
Guo R. 
Lin W.N. 
Yang P. 
Wang J. 
Chow G.M. 
Venkatesan T. 
Tsymbal E.Y.
Tian H.
Chen J.S. 
Issue Date: 1-Dec-2018
Publisher: Nature Publishing Group
Citation: Wang H., Liu Z.R., Yoong H.Y., Paudel T.R., Xiao J.X., Guo R., Lin W.N., Yang P., Wang J., Chow G.M., Venkatesan T., Tsymbal E.Y., Tian H., Chen J.S. (2018-12-01). Direct observation of room-temperature out-of-plane ferroelectricity and tunneling electroresistance at the two-dimensional limit. Nature Communications 9 (1) : 3319. ScholarBank@NUS Repository.
Abstract: Out-of-plane ferroelectricity with a high transition temperature in nanometer-scale films is required to miniaturize electronic devices. Direct visualization of stable ferroelectric polarization and its switching behavior in atomically thick films is critical for achieving this goal. Here, ferroelectric order at room temperature in the two-dimensional limit is demonstrated in tetragonal BiFeO3 ultrathin films. Using aberration-corrected scanning transmission electron microscopy, we directly observed robust out-of-plane spontaneous polarization in one-unit-cell-thick BiFeO3 films. High-resolution piezoresponse force microscopy measurements show that the polarization is stable and switchable, whereas a tunneling electroresistance effect of up to 370% is achieved in BiFeO3 films. Based on first-principles calculations and Kelvin probe force microscopy measurements, we explain the mechanism of polarization stabilization by the ionic displacements in oxide electrode and the surface charges. Our results indicate that critical thickness for ferroelectricity in the BiFeO3 film is virtually absent, making it a promising candidate for high-density nonvolatile memories. � 2018, The Author(s).
Source Title: Nature Communications
ISSN: 2041-1723
DOI: 10.1038/s41467-018-05662-y
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