Structure and morphology of epitaxially intergrown (100)- and (116)-oriented SrBi₂Ta₂O₉ ferroelectric thin films on SrLaGaO₄(110) substrates

SrBi₂Ta₂O₉ (SBT) epitaxial thin films having a mix of (100) and (116) orientations have been grown on SrLaGaO₄(110) by pulsed laser deposition. X-ray diffraction θ-2θ and pole figure scans, and cross-sectional transmission electron microscopy (TEM) analyses revealed the presence of two epitaxial orientations, SBT(100) ∥ SLG(110); SBT[001] ∥ SLG[001] and SBT(116) ∥ SLG(110); SBT[1̄10] ∥ SLG[001]. By calculating the integrated intensity of certain x-ray diffraction peaks, it was established that the crystallinity and the in-plane orientation of the (100) and (116) orientation are best at a substrate temperature of 775°C and 788°C, respectively, and that the volume fraction of the (100) orientation at about 770°C reached about 60%. By scanning force microscopy and cross-sectional TEM investigations we found that the a-axis-oriented grains are rounded and protrude out due to the rapid growth along the [110] direction, leading to a distinct difference of the surface morphology between (100)- and (116)-oriented grains.