Submicron YBCO Josephson junctions on sapphire bicrystal substrates for microwave devices

Submicron YBCO bicrystal Josephson junctions (JJ) and devices for high frequency applications were designed, fabricated and experimentally studied. The key elements of these devices are bicrystal sapphire substrates with symmetric misorientation angles 14.2 , 18.4 and 24 which were fabricated by a solid-state intergrowth method. A technological process based on deep ultraviolet photolithography using a hard carbon mask was developed for the fabrication of 0.4–0.6 lm wide JJ. The junctions have normal resistances up to 2 kX, IcRn > 2 mV and a 1 mV/U0 SQUID response at 4.2 K. The junctions were used as Josephson detectors and spectrometers at frequencies up to 1.5 THz, dc SQUID RF amplifiers operating at 1.5 GHz and submillimeter wave array oscillators. 2002 Elsevier Science B.V. All rights reserved.