Focused ion beam etching has been used to pattern dc SQUIDs into previously characterised template bi-epitaxial grain boundary junctions. In this way, the screening parameter βL can be optimised for a chosen temperature (in our case 30 K). Electrical characteristics, including noise measurements, are presented. A minimal white noise level of 22 μφ0·Hz12 (1.8·10-29 J·Hz-1) has been obtained at 20 K. Using bias current modulation the 1/f noise could be almost completely suppressed down to 1 Hz in the entire temperature range (10–65 K).
IJsselsteijn, R. P. J., Hilgenkamp, J. W. M., Veldhuis, D., Flokstra, J., & Rogalla, H. (1994). High Tc bi-epitaxial dc SQUIDs structured by focused ion beam etching from single junctions: βL optimization. Physica C, 235-240(5), 3353-3354. https://doi.org/10.1016/0921-4534(94)91203-3