The short coherence length of the high-Tc superconductors, coupled with their tendency to form non-superconducting surface layers, accounts for the difficulty in achieving good tunnel junctions. A proximity layer of a longer coherence length normal metal (N) is expected to "draw out" Cooper pairs. Our goal is to fabricate reproducible, planar tunnel junctions of SNIS layered structures for proximity tunneling spectroscopy. Such structures of YBCO/N/I/Pb and SNS structures of YBCO/N/Pb indicate that the normal metal produces a low resistance contact to the YBCO surface with a supercurrent observed in the SNS. The insulating barrier in the SNIS is reproducible, insulating and continuous: A sharp Pb gap and phonons from the counter-electrode are routinely observed.
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics
- Energy Engineering and Power Technology
- Electrical and Electronic Engineering