Adjustable tunneling barrier in bi-based high-T_c cross-whisker junctions

We present a study of cross-whisker junctions with electronically modified tunneling barriers. Cross-whisker junctions were successfully prepared by annealing two crossed Bi-based whisker bars at temperatures of around 840 °C. In addition to the artificially produced junction at the interface, intrinsic Josephson junctions in the respective bars of the cross were observed. The artificial junction exhibited reproducible and almost ideal junction characteristics. The tunneling barrier/interface properties were controlled by carrier injection in c-axis direction. Using this process, we were able to reduce the tunneling resistance from 408 Ω to 30 Ω. At the same time, the critical current did rise by a factor of 4. Subsequently, the critical current was doubled while the tunneling resistance stayed constant. We interpret this observation in terms of the counter-play between transparency of the barrier and the carrier concentration of the electrodes. In this sense, we can consider the current injection procedure as an electronic gluing process of the two cross-junction whisker bars. (paper)