Abstract
Theoretical predictions-motivated by recent advances in epitaxial engineering-indicate a wealth of complex behaviour arising in superlattices of perovskite-type metal oxides. These include the enhancement of polarization by strain and the possibility of asymmetric properties in three-component superlattices. Here we fabricate superlattices consisting of barium titanate (BaTiO3), strontium titanate (SrTiO3) and calcium titanate (CaTiO3) with atomic-scale control by high-pressure pulsed laser deposition on conducting, atomically flat strontium ruthenate (SrRuO 3) layers. The strain in BaTiO3 layers is fully maintained as long as the BaTiO3 thickness does not exceed the combined thicknesses of the CaTiO3 and SrTiO3 layers. By preserving full strain and combining heterointerfacial couplings, we find an overall 50% enhancement of the superlattice global polarization with respect to similarly grown pure BaTiO3, despite the fact that half the layers in the superlattice are nominally non-ferroelectric. We further show that even superlattices containing only single-unit-cell layers of BaTiO3 in a paraelectric matrix remain ferroelectric. Our data reveal that the specific interface structure and local asymmetries play an unexpected role in the polarization enhancement.
| Original language | English |
|---|---|
| Pages (from-to) | 395-399 |
| Number of pages | 5 |
| Journal | Nature |
| Volume | 433 |
| Issue number | 7024 |
| DOIs | |
| State | Published - Jan 27 2005 |
Funding
Acknowledgements We are grateful to J. Brujić for many discussions. This work is supported by the National Science Foundation, Materials Theory. S.H. thanks the Israel Science Foundation and ONR for support. Acknowledgements This work was supported by the US Department of Energy under contract with the Oak Ridge National Laboratory, managed by UT-Battelle, LLC, as part of a BES NSET initiative on Nanoscale Cooperative Phenomena and of the LDRD programme. Acknowledgements This work was funded by grants from the National Institutes of Health (to A.S.V.) and by a Wellcome Trust Clinician Scientist Fellowship (to M.C.P., sponsored by S. Krishna).