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Emergence of room-temperature ferroelectricity at reduced dimensions

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Science  18 Sep 2015:
Vol. 349, Issue 6254, pp. 1314-1317
DOI: 10.1126/science.aaa6442

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Thinning films induces ferroelectricity

Thin ferroelectric films are needed in computers and medical devices. However, traditional ferroelectric films typically become less and less polarized the thinner the films become. Instead of using a good ferroelectric and making it thinner, Lee et al. started with SrTiO3, which in its bulk form is not ferroelectric. This material does have naturally occurring nanosized polarized regions. and when the thickness of the SrTiO3 films reaches the typical size of these regions, the whole film aligns and becomes ferroelectric.

Science, this issue p. 1314

Abstract

The enhancement of the functional properties of materials at reduced dimensions is crucial for continuous advancements in nanoelectronic applications. Here, we report that the scale reduction leads to the emergence of an important functional property, ferroelectricity, challenging the long-standing notion that ferroelectricity is inevitably suppressed at the scale of a few nanometers. A combination of theoretical calculations, electrical measurements, and structural analyses provides evidence of room-temperature ferroelectricity in strain-free epitaxial nanometer-thick films of otherwise nonferroelectric strontium titanate (SrTiO3). We show that electrically induced alignment of naturally existing polar nanoregions is responsible for the appearance of a stable net ferroelectric polarization in these films. This finding can be useful for the development of low-dimensional material systems with enhanced functional properties relevant to emerging nanoelectronic devices.

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