High performance DC superconducting quantum interference device utilizing a bicrystal junction with a 30 degrees misorientation angle

A high T-c de superconducting quantum interference device (SQUID) was fabricated using a bicrystal junction with a misorientation angle of theta = 30 degrees. The junction with a width of 2 mu m exhibited high resistance R-s = 10 Omega and critical current I-0 = 25 mu A at T = 77 K. This gives a I0Rs as high as 250 mu V. These values indicate that the bicrystal junction has great potential for the development of high performance SQUIDs. The SQUID fabricated with a 30 degrees junction exhibited voltage modulation depths as high as Delta V = 85 mu V, 40 mu V and 20 mu V at T = 77 K for the inductance values of L-s = 60 pH, 100 pH and 160 pH, respectively. These are the highest values reported so far. Preliminary noise measurement showed that the Bur noise of the SQUID is less than 8 mu Phi(0)/Hz(1/2) for the white noise region, and less than 70 mu Phi(0)/Hz(1/2) at f = 1 Hz when the 60 pH-SQUID is de biased and operated with a conventional Flux Locked Loop (FLL) circuit.