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Room-Temperature Ferroelectricity in Croconic Acid Films

Molecular ferroelectrics have
the potential to become viable material alternatives to inorganic
ferroelectrics. Unlike traditional oxide ferroelectrics, molecular
ferroelectrics are structurally flexible, can be engineered at the molecular
level, and can be assembled on nearly any surface, including flexible sheets
and fabrics. The application of molecular ferroelectrics hinges, however, on
the availability of strategies to fabricate thin films with defined structure
and morphology on a large scale, which at the same time preserve their
ferroelectric properties.

 Nebraska MRSEC
researchers have demonstrated for the first time the successful growth of a
continuous nanometer thin film of a proton transfer ferroelectric organics,
croconic acid, solvent-free from the vapor phase, while fully maintaining the
material’s ferroelectric properties. The key to success has been the careful
sublimation of croconic acid powder at temperatures that are far below the
melting point. Ferroelectric testing of the films at room temperature shows a
polydomain structure which can be manipulated locally, at the level of
individual nanocrystals, by applying a voltage pulse to the tip of an atomic
force microscope. The application of the solvent-free growth protocol to
molecular ferroelectric thin films is scalable and may be key to the
development of flexible and bendable ferroelectric thin films for electronics

IRG2 Nebraska highlight 2016

Ferroelectric polarization map of a selected
region of a 30 nm thin film of croconic acid measured before (top) and after
(bottom) local application of a voltage pulse.