Polarization switching in BaTiO3thin films measured by X-ray diffraction exploiting anomalous dispersion

Films of BaTiO3ranging from 20 nm to 300 nm in thickness were grown with pulsed laser deposition on Nb:SrTiO3. The quality of the layers was investigated using atomic force microscopy, X-ray reflectivity and X-ray diffraction. Both the micrographs and the X-ray reflectivity spectra indicate a smooth surface of the layers. The X-ray diffraction profiles measured using synchrotron radiation show features characteristic for highly crystalline thin films. The application of an external electric field parallel to thecaxis changes anhklreflection of BaTiO3to anhkl̄ reflection. Due to the anomalous dispersion, the intensities of these two reflections are not equal and the atomic displacements can be determined from the intensity differences. The electric field-induced intensity changes can be as large as a few percent, which makes data collection from a 100 nm film using CuKα radiation from an X-ray tube feasible. The ΔI/Ivalues of a number of reflections from the 20 and 50 nm films were measured using synchrotron radiation. The observed ΔI/Ivalues were in good agreement with the intensity changes expected for polarization switching in the bulk.