Epitaxial Growth and High-Frequency Properties of YBa2Cu3O7 Electrodes on LiNbO3

Epitaxial YBa2Cu3O7 (YBCO) thin films were deposited on electro-optic X-cut LiNbO3 (LNO) single crystals by pulsed laser deposition. A double buffer layer of yttria-stabilized zirconia (YSZ) and CeO2 was found necessary to grow high quality superconducting films. The YSZ layer prevents diffusion from the substrate to the YBCO, although promotes the formation of LiNb3O8 at the interface. The CeO2 top buffer layer is required to avoid the nucleation of two different YBCO crystal domains, 450 rotated. When growth is on the double buffer layer, the YBCO films are epitaxial, with the c axis perpendicular to the surface and single in-plane orientation. The films are superconducting at temperatures above 85 K, with critical current densities of 3x10(5) A/cm(2) at 77 K (6x10(6) A/cm(2) at 5 K). A surface resistance below 1.5 mOmega was measured at 8 GHz and 65 K, making these films promising candidates as electrodes in photonic and acoustic devices.