Effects of ultrathin tantalum seeding layers on sol-gel-derived SrBi ₂Ta₂O₉ thin films

The effects of Ta seeding layer on the crystalline microstructure and ferroelectric properties of sol-gel-derived strontium-bismuth-tantalate (SBT) thin films were investigated. Ultrathin (<1 nm) Ta seeding layers were deposited onto Pt/TiO₂/SiO₂/Si substrates by magnetron sputtering at room temperature before spin coating of SBT thin films. Our results show that the presence of Ta seed layer induces significant changes in the crystallinity and microstructure of the resultant SBT thin films, resulting in improved ferroelectric properties in terms of spontaneous polarization. Interestingly, the remanent polarization (2P_r) of SBT films is also found to initially increase and then decrease with increasing Ta thickness, showing a peak value of 18.8 μC/cm² (@5 V) at Ta thickness of around 0.23 nm. Since a stoichiometric SBT solution was employed in our experiments, the additional Ta on the Pt surface is thought to provide a Ta-rich environment for SBT films, which, in turn, results in lower nucleation activation energy for crystallization.