Superconductivity and electric field effect of 90 degree grain boundaries in YBa2Cu/sub 3/O/sub 7-x/ thin films

A three terminal device was fabricated by depositing YBa/sub 2/Cu/sub 3/O/sub 7-x/ (YBCO) thin films containing 90 degree grain boundaries which was covered with a SrTiO/sub 3/ gate layer and an Au gate electrode. YBCO thin films were grown by bi-epitaxial process on LaSrGaO/sub 4/(100) substrate. The resistance versus temperature curve of the YBCO microbridge containing 90 degree grain boundaries showed double resistive transitions. This result was interpreted by the weak link effect of 90 degree grain boundaries in YBCO thin films. A large electric field effect on 90 degree grain boundaries was observed. The superconducting transition temperature of the 90 degree grain boundaries was modulated up to 11.4% by applying an electric field of 4/spl times/10/sup 4/ V/cm.