TUNNELING SPECTROSCOPY OF SUPERCONDUCTING Y1-XPRXBA2CU3O7 THIN-FILMS

A systematic study of the conductance of Y1-xPrxBa2Cu3O7/Pb planar tun nel junctions as a function of Pr concentration, x, and crystallograph ic orientation is presented. For fixed Pr concentration, the tunneling conductance is the same when tunneling into (100)-, (110)-, and (103) -oriented films, but qualitatively different than tunneling into (001) -oriented films. In addition, the gap-like feature energy (similar to 2k(B)T(c)) scales with T-c, but only when tunneling in the ab-plane di rection. An ongoing experiment characterizing a novel tunnel junction fabrication technique using self-assembled monolayers as insulating tu nnel barriers is also discussed.