Epitaxial growth of YBa₂Cu₃O_7-δ thin films on silicon-on-insulator substrates by pulsed laser deposition

High quality superconducting YBa₂Cu₃O _7-δ (YBCO) thin films have been successfully deposited on silicon-on-insulator (SOI) substrates buffered by an yttria-stabilized zirconia (YSZ) layer using the in situ pulsed laser deposition (PLD) method. X-ray diffraction (XRD) θ-2θ-scan and φ-scan, and reflection high energy electron diffraction (RHEED), indicate that both the YSZ and YBCO thin films are of high crystallinity and good lattice orientation. Atomic force microscopy (AFM) shows that the root mean square roughness R_q of YSZ thin films is less than 0.9 nm in an area of 1 μm × 1 μm, and that of YBCO thin films is about 3 nm in an area of 2 μm × 2 μm. The zero-resistance temperature 7_C0 of the YBCO/YSZ/SOI multilayers is up to 88 K, measured by a four-probe method. However, scanning electron microscopy (SEM) demonstrates many clear cracks in YBCO thin films due to the lattice constant and thermal expansion coefficient mismatch between SOI and YBCO. The crack width changes with the thickness of YBCO thin films.