Does theory lead experiments or do experiments lead theory? Scientists know
the correct answer is that interplay between theory and experiments result in
new advances. At times, experiment and technological development pave the way
for theory. At other times, successful theory can contribute substantially to
interpretation and analysis of the experimental data.
But even more important is when theory can predict new effects and lead to
new experiments and developments. This is evident in the new work at the University
of Nebraska-Lincoln Materials Research Science and Engineering Center published
in the scientific journal Nano Letters.
Three years ago, theoretical work of a research group of UNL physics and astronomy
professor Evgeny Tsymbal predicted a new effect that could revolutionize the
field of microelectronics by allowing faster, smaller and more energy-efficient
memory devices. Recently, measurements of the electrical properties of ferroelectric
materials performed at the Alexei Gruverman lab led to experimental verification
of the predicted behavior. In their paper published online Aug. 21 in Nano Letters,
Gruverman, an associate professor of physics and astronomy, and Tsymbal, with
co-authors demonstrated a several-orders-of-magnitude change in electrical resistance
upon flipping of polarization in ultra-thin ferroelectric films.
Because of their ability to retain permanent electric polarization in the absence
of the electric field, for decades ferroelectrics have been the subject of intense
development for use in nonvolatile memory, where tiny bits of information are
stored as polarization dipoles oriented up and down. The effect discovered at
the UNL center could help overcome one of the most serious problems related
to miniaturization of charge-based memory technologies ‚Äî
reduced charge and increasing leakage current ‚Äî that leads
to larger power consumption and progressive loss of stored information. In fact,
it can turn this problem into an advantage because it will allow nondestructive
read-out of the polarization state of the film simply by measuring its electrical
resistance, which can be performed at a significantly lower voltage.
Application of the advanced measurements techniques showed that a single bit
of information can be as small as 20 nanometers in diameter (1/1000th diameter
of a human hair).
The ferroelectric films for this study were grown by collaborators at the University
of Wisconsin, Madison. Funding from the National Science Foundation helps support
Links to the two papers referenced are: http://www.sciencemag.org/cgi/content/summary/313/5784/181