High Performance dc SQUID Fabricated on SrTiO3 Bicrystal Substrate with 30° Misorientation Angle

A high performance high T c dc SQUID was fabricated using a bicrystal junction with a misorientation angle of θ=30°. The bicrystal junctions showed junction resistance R s=10 Ω and critical current I o=25 µA (I o R s =250 µV) at T=77K when junction width is w=2 µm. The SQUID exhibited voltage modulation depths as high as ΔV=85 µV, 50 µV and 20 µV at T=77 K for the inductance values of L s=60 pH, 100 pH and 160 pH, respectively. Preliminary noise measurement showed that the flux noise of the SQUID is less than 10µΦo /Hz1/2 in the white noise region for the case of L s=100 pH. These results indicate that the bicrystal junction with a misorientation angle of θ=30° has great potential for the development of high performance SQUIDs.