Interface-Modified Ramp-Type Josephson Junctions in Trilayer Structures(<特集>Special Issue on Superconductive Electronics)

We have fabricated ramp-type Josephson junctions in trilayer structures. A bilayer of YBa_2Cu_3O_ (YBCO)/CeO_2 was deposited on a SrTiO_3 (100) substrate. Then, circle patterns with a diameter of 2 μm were etched on the bilayer surface using standard photolithography process. During the Ar ion milling with an incident angle of 45 degrees to the bilayer surface, the sample was rotated. This process led to upside-down conical formations. After the ramp-edge surface was modified, another YBCO film was deposited for the top electrode. The junctions showed the I-V characteristics between resistively shunted junction and flux-flow types.We have fabricated ramp-type Josephson junctions in trilayer structures. A bilayer of YBa_2Cu_3O_ (YBCO)/CeO_2 was deposited on a SrTiO_3 (100) substrate. Then, circle patterns with a diameter of 2 μm were etched on the bilayer surface using standard photolithography process. During the Ar ion milling with an incident angle of 45 degrees to the bilayer surface, the sample was rotated. This process led to upside-down conical formations. After the ramp-edge surface was modified, another YBCO film was deposited for the top electrode. The junctions showed the I-V characteristics between resistively shunted junction and flux-flow types