a1 Materials Research Institute, The Pennsylvania State University, University Park, Pennsylvania 16802-5005
a2 Department of Physics, Boise State University, Boise, Idaho 83725
a3 Department of Materials Science and Engineering, University of Michigan, Ann Arbor, Michigan 48109
a4 Department of Materials Science and Engineering, University of Wisconsin, Madison, Wisconsin 53706
a5 Materials Science and Technology Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545
a6 Department of Physics, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213
a7 Institute for Crystal Growth, Max-Born-Straße 2, D-12489 Berlin, Germany
Commensurate BaTiO3/SrTiO3 superlattices were grown by reactive molecular-beam epitaxy on four different substrates: TiO2-terminated (001) SrTiO3, (101) DyScO3, (101) GdScO3, and (101) SmScO3. With the aid of reflection high-energy electron diffraction (RHEED), precise single-monolayer doses of BaO, SrO, and TiO2 were deposited sequentially to create commensurate BaTiO3/SrTiO3 superlattices with a variety of periodicities. X-ray diffraction (XRD) measurements exhibit clear superlattice peaks at the expected positions. The rocking curve full width half-maximum of the superlattices was as narrow as 7 arc s (0.002°). High-resolution transmission electron microscopy reveals nearly atomically abrupt interfaces. Temperature-dependent ultraviolet Raman and XRD were used to reveal the paraelectric-to-ferroelectric transition temperature (TC). Our results demonstrate the importance of finite size and strain effects on the TC of BaTiO3/SrTiO3 superlattices. In addition to probing finite size and strain effects, these heterostructures may be relevant for novel phonon devices, including mirrors, filters, and cavities for coherent phonon generation and control.
(Received January 29 2008)
(Accepted February 12 2008)
b) Present address: Seagate Technology, Bloomington, MN 55437.
c) Present address: USAID, Washington, DC 20523.