Improvement of junction properties of YBaCuO/PrBaCuO/YBaCuO trilayer Josephson junctions

We have demonstrated improvement of junction properties for YBaCuO/PrBaCuO/YBaCuO trilayer junctions, using a backing plate of Al and Cu stacked foils between substrate and sample holder to ensure uniform substrate temperature during deposition of trilayer films, and by controlling film composition precisely to reduce the precipitated particles on the surface of the films. All junctions with a barrier thickness of 35 nm and dimensions of less than 10 /spl mu/m/spl times/10 /spl mu/m showed RSJ-like current-voltage characteristics with some excess currents at 4.2 K. Typical values of Josephson critical current density J/sub c/ as measured using a magnetic modulation of total critical current density, and normalized junction resistance R/sub n/A were 2.4/spl times/10/sup 3/A/cm/sup 2/ and 1.8/spl times/10/sup -7//spl Omega/cm/sup 2/ at 4.2 K, respectively. For the 88 junctions on the substrate, the 1-/spl sigma/ spreads of J/sub c/ and R/sub n/A were obtained to be 34% and 25%, respectively.