ELECTRIC-FIELD EFFECT AND TRANSPORT-PROPERTIES OF A 90-DEGREES GRAIN-BOUNDARY IN YBA2CU3O7-X THIN-FILMS

We have investigated the influence of a 90 degrees grain boundary in Y Ba2Cu3O7-x (YBCO) thin films on the transport properties and electric field effect. A superconducting field effect device structure with a 9 0 degrees grain boundary in YBCO thin films, covered with an SrTiO3 ga te layer, was fabricated by pulsed laser deposition. The 90 degrees gr ain boundary was formed by the selective growth of the c-axis and in-p lane aligned, a-axis-oriented YBCO films on the same LaSrGaO4 (100) su bstrate with b-axis-oriented PrBa2Cu3O7-x patterns. The resistance ver sus temperature curve of the YBCO microbridge with a 90 degrees grain boundary showed a significant decrease of the zero resistance temperat ure (T-c,T-o) to 35 K as well as broadening of the superconducting tra nsition width compared to the c-axis- and a-axis-oriented YBCO thin fi lm sections. By applying a gate voltage of 1 V, the superconducting tr ansition temperature of the YBCO channel containing 90 degrees grain b oundary was modulated up to 11.4%