Pulsed laser deposition of ultrathin BaTiO3/Fe bi-layers: Structural characterization and piezoelectric response

Ferroelectric ultrathin BaTiO3 (BTO) films in contact with Fe underlayer have been grown by pulsed laser deposition onto MgO(100) substrates in a single vacuum cycle. The structural properties of the composite system are investigated by Rutherford backscattering spectrometry/channeling and cross-sectional transmission electron microscopy. The BTO band gap is measured by in situ reflection electron energy loss spectroscopy to be Eg = 4.1-4.3 eV depending on the growth conditions. The ferroelectric nature of BTO (thickness down to 3 nm) on top of Fe is demonstrated by piezoresponse force microscopy, which shows an out-of-plane piezoelectric coefficient of 17 ± 4 pm/V. The obtained results are promising in the view of integrating BTO/Fe stacks in functional ferroelectric tunnel junctions.