Confocal scanning optical microscopy of BaxSr1−xTiO3 thin films

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Abstract
An optical technique based on confocal scanning optical microscopy (CSOM) is used to image the ferroelectric polarization of BaxSr1−xTiO3 (BST) thin films at room temperature with submicron spatial resolution. BST films were grown by pulsed laser deposition on (100) SrTiO3 and MgO substrates at 750 °C in 300 mTorr of oxygen and postdeposition annealed in flowing oxygen at temperatures ⩽1250 °C. Films of both paraelectric (x=0.5) and ferroelectric (x=0.8) compositions show a coexistence of both paraelectric and ferroelectric phases. The ferroelectric regions exhibit polarization switching and hysteresis at relatively low (1–2 kV/cm) applied fields. These results suggest that nonuniform stress is responsible for the strong inhomogeneous thermal broadening of the ferroelectric phase transition, and that dielectric loss in thin films may be dominated by a relatively small fraction of nanometer-sized regions.