SUPERCONDUCTIVITY AND ELECTRIC-FIELD EFFECT OF 90 DEGREE GRAIN-BOUNDARIES IN YBA2CU3O7-X THIN-FILMS

three terminal devise was fabricated by depositing YBa2Cu3O7-x (YBCO) thin films containing 90 degree grain boundaries which was covered wit h a SrTiO3 gate layer and an Au gate electrode. YBCO thin films were g rown by bi-epitaxial process on LaSrGaO4(100) substrate. The resistanc e versus temperature curve of the YBCO microbridge containing 90 degre e grain boundaries showed double resistive transitions. This result wa s interpreted by the weak link effect of 90 degree grain boundaries in YBCO thin films. A large electric field effect on 90 degree grain bou ndaries was observed. The superconducting transition temperature of th e 90 degree grain boundaries was modulated up to 11.4% by applying an electric field of 4 x 10(4) V/cm.