JOSEPHSON EFFECTS IN YBA2CU3OY GRAIN-BOUNDARY JUNCTIONS ON (100)MG0 BICRYSTAL SUBSTRATES

The grain boundary YBa2Cu3Oy(YBCO) Josephson junctions are fabricated on (100)MgO bicrystal substrates with a misorientation angle of 24°and the microwave properties of Josephson effects are studied up to millimeter-wave range. Strong [100]//[010] and [010]//[100] in-plane orientations are observed at the junction interface of a YBCO film, whose microscopic geometries are discussed in connection with the observed Josephson effects. The directly observed maximum Josephson microwave self-radiation powers from the junction at receiver frequencies of fREC=22 GHz and 47 GHz are 3.2×10-12 W and 5.6×10-14 W, respectively. The observed characteristic voltage (Vc) is 4.4 mV, corresponding to the frequency of about 2 THz at 4.2 K.© 1995 American Institute of Physics.