HTSC Josephson junctions and dc SQUIDs on SrTiO3 bicrystal substrates grown by floating zone method

A new approach to the fabrication of a SrTiO3 bicrystal substrate based on the technology of growing by floating zone method natural SrTiO3 bicrystals with misorientation angles 24 degrees and 37 degrees has been developed. Thin film YBCO Josephson junctions and dc SQUIDs on SrTiO3 bicrystal substrates were fabricated and studdied at T = 77 K. A critical current density j(c) and I(c)R(n) product for the junctions with misorientation angle alpha = 24 degrees were close to 2 x 10(4) A/cm(2) and 190 divided by 260 mu V respectively, while for alpha = 37 degrees it were found that j(c) approximate to 2 x 10(3) A/cm(2) and I(c)R(n) approximate to 90 divided by 120 mu V. The dc SQUIDs were made with typical inductances 20 divided by 80 pH, critical currents of 20 divided by 150 mu A and resulting voltage modulation 10 divided by 40 mu V. Noise measurements performed at 77 K revealed low 1/f noise with cut-off frequency about 10 H z.