Enhanced Ferroelectric Stability by Interface Engineering
A. Gruverman and E. Y. Tsymbal (Nebraska MRSEC)
C.-B. Eom (University of Wisconsin)
X. Pan (University of Michigan)
Ferroelectric materials are characterized by a spontaneous polarization
that can be switched by external electric field. This property is
important for various technological applications such ferroelectric
random access memories. However, when ferroelectric film thickness
is reduced down to a nanoscale the ferroelectric polarization may
become unstable due to strong depolarization fields and interface
effects.
Nebraska MRSEC researchers in collaboration with their colleagues
at Universities of Wisconsin and Michigan have predicted and
demonstrated that interface engineering may be efficiently used to
stabilize ferroelectric polarization at the nanoscale. Using sophisticated
first-principles
calculations
and
advanced
fabrication
and
characterization techniques the researchers showed that deposition of
a two-unit cell thick non-ferroelectric strontium titanate layer at the
interface enhances the polarization of ferroelectric barium titanate
layer, making it switchable by an applied electric filed. This discovery
provides a new insight into the switching and retention behavior of thinfilm ferroelectric materials and paves the way to atomic scale property
engineering in ferroelectric-based electronic devices. This work was
partly supported by the Nanoelectronics Research Initiative of
Semiconductor Research Corporation.
Experimental observation of enhanced
polarization of a barium titanate thin film.
Left images have the same contrast
indicating that polarization of barium
titanate is not switched by electric field.
Right images have different contrast
indicating that the interface engineered
film can be switched by an electric field.
These programs are supported by the National Science Foundation, Division of Materials Research, Materials
Research Science and Engineering Program, Grant 0820521.