Growth of nanoscale BaTiO3/SMO3 superlattices by molecular-beam epitaxy

Abstract

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 soperlattices 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-ferroeleotric 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 phooon devices, including mirrors, filters, and cavities for coherent phonon generation and control.