Pulsed Laser Deposition of Ba2Cu3O7-δ/BaTiO3/YBa2Cu3O7-δ Multilayer Structure on Si(100) Substrates

We have studied materials issues relevant to the applications of YBCO/BTO/YBCO multilayer structures, including multilayer HTS circuits and crossovers, nonvolatile memories, and on-chip energy storage for Si solar cells. Due to the good lattice match between BTO and YBCO, epitaxial YBCO/BTO multilayer device structures are possible. We have deposited YBCO/BTO/YBCO capacitors onto YSZ buffered Si substrates by using pulsed laser deposition technique. All four oxide layers are grown in situ without breaking the vacuum, and without lowering the substrate temperature to below 600°C. We have achieved sharp resistive transitions for both the top and the bottom YBCO layers with onset at 90 K, zero resistance at 89 K for the bottom layer and 88 K for the top layer. X-ray diffraction data indicate that all four deposited oxide layers have their c-axis perpendicular to the substrate, and have less that 10% in-plane misorientation. The BTO layer shows a dielectric constant of 210, a leakage constant of 5 × 10-7A/cm2at 10 Volts, and a remanent polarization of 2 6µC/cm2.