Thin-film anisotropic transport measurement on tilted ${\mathrm{Bi}}_2$${\mathrm{Sr}}_2$${\mathrm{CaCu}}_2$${\mathrm{O}}_{\mathit{x}}$

To make a relevant transport measurement between adjacent Cu-O (or double Cu-O) layers, a high-quality single-crystal sample with a rather small area having a restricted number of Cu-O layers is required. To satisfy such requirements, we have prepared a tilted epitaxial ${\mathrm{Bi}}_2$ ${\mathrm{Sr}}_2$ ${\mathrm{CaCu}}_2$ ${\mathrm{O}}_{\mathit{x}}$ film. The c axis of the film makes a nonzero angle with respect to the film normal. In a certain direction, the transport current has to traverse Bi-O layers. Few-micrometer-wide strips containing several tens of Cu-O layers in series were made. The resistivities, critical currents, and I-V characteristics showed marked anisotropies in two transport orientations. The possibility of direct observation of interlayer Josephson coupling was investigated. However, no ac or dc Josephosn effect was observed. The voltage near ${\mathit{I}}_{\mathit{c}}$ seemed to be generated by the dynamics of the Josephson vortices. These observations are consistent with a theoretical analysis based on the Josephson-coupled layered model, which gives a Josephson penetration depth considerably smaller than our smallest sample size, and a transport analysis considering the detailed junction geometry.