Misorientation dependence of DC SQUID of YBa/sub 2/Cu/sub 3/O/sub 7-X/ grain boundary junctions on MgO bicrystal substrates

Thermal diffusion-bonded bicrystals of MgO with the configuration of [00l] tilt boundaries were incorporated as substrates to create artificial grain boundaries of epitaxial YBa/sub 2/Cu/sub 3/O/sub 7-X/ (YBCO) thin films. The transport properties of the YBCO grain boundary junctions across various misorientation angles /spl Theta/, /spl Theta/=10/spl deg/, 20/spl deg/, 30/spl deg/, 40/spl deg/, have been studied. The critical current density across the grain boundaries decreased exponentially as the misoriented angle increasing. The current-voltage characteristics of the /spl Theta/=10/spl deg/, 20/spl deg/ grain boundary junctions typically exhibited flux-flow or flux-creep like behavior; and the /spl Theta/=30/spl deg/, 40/spl deg/ grain boundary junctions revealed a resistive shunted junction (RSJ) like I-V characteristics. The transition from strong coupling for low angle grain boundary to weak-link behavior occurred with /spl Theta/>20/spl deg/. The dc SQUIDs made of /spl theta/=30/spl deg/ and 40/spl deg/ misoriented grain boundary showed periodic modulation of voltage-flux characteristics up to 77 K, IcRn = 0.4 mV, with /spl Delta/V=6 /spl mu/V.