The Importance of In Situ Monitors in the Preparation of Layered Oxide Heterostructures by Reactive MBE

Using a variety of in situ monitors and when possible adsorption-controlled growth conditions, layered oxide heterostructures including new compounds and metastable superlattices have been grown by reactive molecular beam epitaxy (MBE). The heteroepitaxial layers grown include Bi 4 Ti 3 O 12 −SrTiO 3 and Bi 4 Ti 3 O 12 −PbTiO 3 Aurivillius phases, Sr n+1 Ti n O 3n+1 Ruddlesden-Popper phases, and metastable PbTiO 3 / SrTiO 3 and BaTiO 3 / SrTiO 3 superlattices. Accurate composition control is key to the controlled growth of such structures, and to this end combinations of reflection high-energy electron diffraction (RHEED), atomic absorption spectroscopy (AA), a quartz crystal microbalance (QCM), and adsorption-controlled growth conditions were employed during growth. The structural perfection of the films has been investigated using in situ RHEED, four-circle x-ray diffraction, atomic force microscopy (AFM), and high-resolution transmission electron microscopy (TEM).