Pulsed laser deposition (PLD) of ferroelectric thin films in conjunction with superconducting oxides

The possibility of combining ferroelectrics and superconductors has been of interest for use in memory storage devices. Additionally, superconductors offer crystal structures compatible to the epitaxial growth of the ferroelectric, Ba_0.6Sr_0.4TiO₃ (BSTO), which is cubic at this stoichiometry. BSTO has a lattice constant of 3.94 Å as compared to the superconducting Pr_2-x Ce_xCuO₄ tetragonal single crystal which also has a lattice constant of a=3.94 Å. In this study, ferroelectric thin films of BSTO were deposited on single crystals of Pr₂CuO₄ and Pr_2-xCe_xCuO₄. The optical constants of the substrates, single crystals of Pr₂CuO₄ and Pr _2-xCe_xCuO₄, were determined using Variable Angle Spectroscopic Ellipsometry (VASE) and the composition and crystal structure were examined using Rutherford Backscattering Spectrometry (RBS) with ion beam channeling. The substrate/film interfaces and the compositional variation in the films were also studied with RBS and with SEM/EDS. Glancing angle X-ray diffraction was used to verify the epitaxial nature of the films. The effect of the deposition parameters (laser repetition rate, oxygen backfill pressure, and deposition geometry) on the quality of the films was experimented with and the optimized parameters were used