Effect of Ta nanobarrier in magnetron sputtering of Nd-doped SrBi ₂Ta₂O₉ thin films

SrBi₂Ta₂O₉(SBT) is a bismuth layered perovskite with attractive ferroelectric properties for random access memory applications. Our previous studies showed that Nd-doped SBT (SNBT) thin films exhibited an improved remnant polarization and reduced coercivity. This paper concentrates on the effect of Ta nanobarrier in between the SNBT and the Pt layers. Without the nanobarrier, severe bismuth diffusion is revealed by the secondary ion mass spectroscopy. However, with a nano layer (up to 2 nm) of Ta metal, the interfacial diffusion is effectively suppressed even at 800°C. Details of the composition profiling, film crystallinity and remnant polarization are discussed in view of the nanobarrier thickness.