One of the materials that powers modern technology like medical ultrasound and nationwide cell phones has been discovered to retain its properties when present in extraordinarily tiny amounts. This discovery implies that this and other materials with similar properties may be valuable at nanoscale in the production of small, smart communications devices, tiny diagnostic instruments and nano-robots.
These ferroelectric materials have a spontaneous dipole, or charge separation, that allows them to generate an electric current when their shape is changed--thus, mechanical energy becomes electricity. Until now, however, researchers had not determined whether these materials retain their properties at the nanoscale, where quantum physics plays a predominant role and different rules apply.
A group of University of Arkansas physicists has determined that the materials that allow these energy conversions indeed retain their properties at the nanoscale. Huaxiang Fu, assistant professor of physics, and Laurent Bellaiche, associate professor of physics, report their findings in an upcoming issue of Physical Review Letters.
Using computer modeling, Fu and Bellaiche looked at barium titanium oxide (BaTiO3), a typical ferroelectric material.
While they found that BaTiO3 quantum dots would continue to have a dipole at the nanoscale, some differences do exist between the nanoscale material and its bulk counterpart. For instance, the researchers found that converting electricity to mechanical energy—for the specific case studied—is less efficient at the nanoscale than at the classical scale. They also found that, unlike in BaTiO3 bulk, dipoles do not naturally align in the same direction in the nanomaterial, but rather form a vortex pattern. They discovered that the dipoles do align if the researchers use a voltage that is strong enough. The voltage required to make the dipoles line up depends upon the length of the material.
These findings mark the first look at the properties of ferroelectric compounds at the nanoscale and will allow researchers to begin to further explore these properties.
"This is a new field. No one really knows the answers," Fu said.