Ferroelectricity can exist in a sheet of material just a few nanometres thick. This new and unexpected discovery by researchers in the US and South Korea could help in the development of new materials for nanoscale electronics.
Ferroelectric materials have permanent electric dipole moments – much like their ferromagnetic counterparts, which have permanent magnetic dipole moments. Ferroelectrics have the potential to be used in a wide range of devices because their dipole moments can be oriented using electric fields, which are much easier to create than the magnetic fields used to manipulate ferromagnetic materials. One possible application is memory chips that store data in terms of the polarization of ferroelectric thin films. A major problem, however, is that these materials cease to be ferroelectric as they become very thin, which limits their usefulness in modern electronic devices.
The researchers, led by Chang Beom Eom of the University of Wisconsin–Madison, have found that a thin film of a material that is normally not electrically polarized can be made polar by taking advantage of existing tiny polar nanoregions within the material. "This happens when the film is made so thin that its whole volume is occupied by these nanoregions," explains Eom. "When these are electrically aligned in one direction, this leads to a net polarization – and the material becomes ferroelectric."
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