Fabrication of a barium titanate-strontium titanate strained layer superlattice

A thin film superlattice heterostructure composed of alternating BaTiO₃ and SrTiO₃ layers was grown on a thin YBa₂Cu₃O₇ electrode templated on a (100) SrTiO₃ wafer using the pulsed laser deposition method. Stranski-Krastanov nucleation of the layers was demonstrated using atomic force microscopy (AFM) when processing conditions were maintained at 6 millitorr oxygen partial pressure, and 550°C substrate temperatures. High-resolution x-ray diffraction (HRXRD) measurements indicate that all the deformation was concentrated in the BaTiO₃ layers with c/a extension to approximately 1.08. Rutherford backscattering spectroscopy (RBS) results indicate excellent crystallinity in the heterostructure. The microstructural data suggests that the theoretical critical thickness of the film has been surpassed by an order of magnitude.