title: Controlling tetragonality and crystalline orientation in BaTiO₃ nano-layers grown on Si.
abstract: A hybrid growth process was developed in order to epitaxially integrate nano-layers of the multi-functional perovskite BaTiO₃ onto Si(001) substrates. In particular, we combined molecular beam epitaxy (MBE) with radio-frequency sputtering. Due to its strong influence on the functional properties, the crystalline structure of the layers was thoroughly investigated throughout our study. MBE-grown seed layers are tetragonal and c-axis oriented up to a thickness of 20 nm. A transition into a-axis films is visible for thicker layers. When the seed layer thickness exceeds 6 nm, subsequently sputtered BaTiO₃ films are epitaxial. However, their crystalline structure, their orientation with respect to the substrate, and their morphology are strongly dependent on the deposition and post-deposition thermal budget. Consistently with their crystalline symmetry, thin MBE BaTiO₃ films are piezo- and ferroelectric with a spontaneous polarization perpendicular to the surface. Also for thick films, the functional response, as determined via piezo-force microscopy, is in good agreement with the structural properties.
authors.affiliation: IBM Research-Zurich, Säumerstrasse 4, 8803 Rüschlikon, Switzerland. sab@zurich.ibm.com
authors.forename: S
authors.initials: S
authors.lastname: Abel
authors.forename: M
authors.initials: M
authors.lastname: Sousa
authors.forename: C
authors.initials: C
authors.lastname: Rossel
authors.forename: D
authors.initials: D
authors.lastname: Caimi
authors.forename: M D
authors.initials: MD
authors.lastname: Rossell
authors.forename: R
authors.initials: R
authors.lastname: Erni
authors.forename: J
authors.initials: J
authors.lastname: Fompeyrine
authors.forename: C
authors.initials: C
authors.lastname: Marchiori