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Use of an External Electric Field to Convert the Paraelectric Phase to the Ferroelectric Phase in Ultra-thin Copolymer Films of P(VDF-TrFE)

Published online by Cambridge University Press:  21 March 2011

Matt Poulsen
Affiliation:
Department of Physics and Astronomy and Center for Materials Research and Analysis, University of Nebraska, Lincoln, NE 68588
S. Adenwalla
Affiliation:
Department of Physics and Astronomy and Center for Materials Research and Analysis, University of Nebraska, Lincoln, NE 68588
Stephen Ducharme
Affiliation:
Department of Physics and Astronomy and Center for Materials Research and Analysis, University of Nebraska, Lincoln, NE 68588
V.M. Fridkin
Affiliation:
Institute of Crystallography, Russian Academy of Sciences, 117333 Moscow, Russia
S.P. Palto
Affiliation:
Institute of Crystallography, Russian Academy of Sciences, 117333 Moscow, Russia
N.N. Petukhova
Affiliation:
Institute of Crystallography, Russian Academy of Sciences, 117333 Moscow, Russia
S.G. Yudin
Affiliation:
Institute of Crystallography, Russian Academy of Sciences, 117333 Moscow, Russia
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Abstract

X-ray diffraction was used to probe the structural changes associated with the conversion of the paraelectric phase to the ferroelectric phase that results from the application of a large external electric field. The samples under study are ultrathin (150 to 250 Å) Langmuir-Blodgett films of the copolymer vinylidene fluoride (70%) with trifluoroethylene (30%) deposited on aluminum-coated silicon. Theta-2theta X-ray diffraction was used to measure the change in inter-layer spacing perpendicular to the film surface. Upon heating at zero external electric field, the crystalline films undergo a structural phase transition, at 100± 5°C, from the all-trans ferroelectric phase to the trans-gauche paraelectric phase. [1,2] Above the phase transition temperature, the non-polar paraelectric phase can be converted back to the polar ferroelectric phase, in a smooth continuous process, using a large external electric field (∼1 GV/m). For example, at 100° C the ferroelectric phase first appears above 0.2 GV/m and increases steadily in proportion while the paraelectric phase decreases until complete conversion to the ferroelectric phase is achieved at approximately 0.6 GV/m.

Type
Research Article
Copyright
Copyright © Materials Research Society 2001

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References

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