Reviews of topical problems

Two-dimensional ferroelectrics

 a,  a,  a,  b,  b,  b
a Shubnikov Institute of Crystallography, Russian Academy of Sciences, Leninskii prosp. 59, Moscow, 119333, Russian Federaion
b Department of Physics and Astronomy, Behlen Laboratory of Physics, Center for Materials Research and Analysis, University of Nebraska-Linkoln, Linkoln, NE, USA

The investigation of the finite-size effect in ferroelectric crystals and films has been limited by the experimental conditions. The smallest demonstrated ferroelectric crystals had a diameter of ~200 Å and the thinnest ferroelectric films were ~200 Å thick, macroscopic sizes on an atomic scale. Langmuir-Blodgett deposition of films one monolayer at a time has produced high quality ferroelectric films as thin as 10 Å, made from polyvinylidene fluoride and its copolymers. These ultrathin films permitted the ultimate investigation of finite-size effects on the atomic thickness scale. Langmuir-Blodgett films also revealed the fundamental two-dimensional character of ferroelectricity in these materials by demonstrating that there is no so-called critical thickness; films as thin as two monolayers (1 nm) are ferroelectric, with a transition temperature near that of the bulk material. The films exhibit all the main properties of ferroelectricity with a first-order ferroelectric-paraelectric phase transition: polarization hysteresis (switching); the jump in spontaneous polarization at the phase transition temperature; thermal hysteresis in the polarization; the increase in the transition temperature with applied field; double hysteresis above the phase transition temperature; and the existence of the ferroelectric critical point. The films also exhibit a new phase transition associated with the two-dimensional layers.

Text can be downloaded in Russian. English translation is available on IOP Science.
PACS: 75.70.−i, 77.80.−e (all)
DOI: 10.1070/PU2000v043n03ABEH000639
Citation: Blinov L M, Fridkin V M, Palto S P, Bune A V, Dowben P A, Ducharme S "Two-dimensional ferroelectrics" Phys. Usp. 43 243–257 (2000)
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:   ,   ,   ,   ,   ,   « » 170 247–262 (2000); DOI: 10.3367/UFNr.0170.200003b.0247

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