Ultrathin BaTiO3 templates for multiferroic nanostructures

TL;DR

This paper reports on the growth and characterization of ultrathin BaTiO3 films with high structural quality, suitable for multiferroic heterostructures, revealing strain effects and surface properties relevant for magneto-electric applications.

Contribution

It demonstrates the synthesis of high-quality ultrathin BaTiO3 films with controlled thickness and surface properties, enabling advanced multiferroic heterostructure research.

Findings

Ultrathin BaTiO3 films are atomically smooth with large terraces.

A strain-driven transition to 3D island formation occurs at 13 unit cells.

Films exhibit dielectric properties similar to bulk BaTiO3.

Abstract

Structural, electronic and dielectric properties of high-quality ultrathin BaTiO3 films are investigated. The films, which are grown by ozone-assisted molecular beam epitaxy on Nb-doped SrTiO3 (001) substrates and having thicknesses as thin 8 unit cells (3.2 nm), are unreconstructed and atomically smooth with large crystalline terraces. A strain-driven transition to 3D island formation is observed for films of of 13 unit cells thickness (5.2 nm). The high structural quality of the surfaces, together with the dielectric properties similar to bulk BaTiO3 and dominantly TiO2 surface termination, make these films suitable templates for the synthesis of high-quality metal-oxide multiferroic heterostructures for the fundamental study and exploitation of magneto-electric effects, such as a recently proposed interface effect in Fe/BaTiO3 heterostructures based on Fe-Ti interface bonds.