The tunneling spectroscopy of both (Formula presented) (YBCO) and (Formula presented) (Tl-1223) superconducting thin films was studied using scanning tunneling microspectroscopy. The marked staircase structure in the current-voltage characteristics showed the manifestation of single-electron charging of two series-coupled mesoscopic tunnel junctions. For YBCO films, the step width across the zero-bias voltage (Formula presented) was larger than that of other steps (Formula presented) with (Formula presented) as the bias voltage exceeded a threshold value. Such a step-widening anomaly, however, was not seen in Tl-1223 films. Preliminary surface polarization measurements showed that the polarization is much more hysteretic for YBCO than for Tl-1223 films, suggesting that the anomalous widening of (Formula presented) may originate from the polarization-induced residual charging effect.
|Number of pages||4|
|Journal||Physical Review B - Condensed Matter and Materials Physics|
|State||Published - 1 Jan 1998|