Properties of Multilevel Ramp Edge Junctions and SQUIDs with Laser-Ablated SrTiO3 Barriers

We have fabricated junctions and DC SQUIDs using laser ablation for both the YBCO electrodes and the thin SrTiO3(STO) barrier regions in a variety of device configurations. These SQUIDs operate reliably at 77 K and preliminary results on a limited number of devices show that they store reasonably well for periods in excess of one year, and exhibit only small changes with repeated cycles (~ 10) between room temperature and 77 K. Noise measurements made using bias reversing on a SQUID (92 pH) at 77 K give a white noise of about 15 µΦ•/√Hz and a 1/f upturn at about 0.2 Hz. © 1995 IEEE