Improvements in the properties of electron beam damage YBa/sub 2/Cu/sub 3/O/sub 7-/spl delta// junctions

We have considerably improved the properties of our electron beam damage junctions by using a smaller condenser aperture. The better defined beam results in a more concentrated damage profile. Consequently, the junctions have a more resistive barrier and higher current density compared to junctions fabricated with a large aperture. We can now obtain an I/sub c/R/sub n/ value of 2 mV up to a temperature of 50 K. The improved junctions have barriers with T/sub cn/=0 K, and consequently operate over a much wider temperature range. Using the small aperture we have varied the length of the barrier while keeping its resistivity constant. The exponential variation of the critical current of these junctions with length shows that they have an SNS-character with the decay length varying between 3 and 4 nm.