Title :
Reproducible step-edge junction SQUIDs
Author :
Shen, Y.Q. ; Sun, Z.J. ; Kromann, R. ; Holst, T. ; Vase, P. ; Freltoft, T.
Author_Institution :
NKT Res. Centre AS, Brondby, Denmark
fDate :
6/1/1995 12:00:00 AM
Abstract :
High-T/sub c/ superconducting YBCO SQUIDs have been developed based on step-edge junctions. The step-edges were fabricated by using electron-beam lithography and Ar-ion milling on SrTiO/sub 3/ substrates. The V(/spl Phi/) peak-to-peak voltage is around 10 /spl mu/V, and the I/sub c/R/sub n/ product is 150 /spl mu/V at 77 K. The SQUIDs prepared on the same substrate show reproducible parameters within 30%. At 77 K the noise properties of the SQUIDs have been studied. At lower frequencies (1 Hz-100 Hz), we observe a flat noise level just below 10/sup -4//spl Phi//sub 0//Hz/sup 1/2/ probably limited by switching effects. Above 100 Hz the noise is gradually reduced to 10/sup -5//spl Phi//sub 0//Hz/sup 1/2/ at 1 kHz. The geometry of the step-edges has also been investigated by scanning electron microscopy, and the relation between the properties of the SQUID and the step height is reported.<>
Keywords :
SQUIDs; barium compounds; critical current density (superconductivity); electron beam lithography; high-temperature superconductors; ion beam applications; scanning electron microscopy; superconducting device noise; superconducting device testing; yttrium compounds; 1 Hz to 1 kHz; 10 muV; 77 K; Ar-ion milling; I/sub c/R/sub n/ product; SrTiO/sub 3/; SrTiO/sub 3/ substrates; YBa/sub 2/Cu/sub 3/O/sub 7/; critical current density; electron-beam lithography; flat noise level; high-T/sub c/ superconducting YBCO SQUIDs; noise properties; peak-to-peak voltage; reproducible step-edge junction SQUIDs; scanning electron microscopy; step height; step-edge geometry; switching effects; Frequency; Josephson junctions; Lithography; Milling; Noise level; Noise reduction; SQUIDs; Superconducting device noise; Voltage; Yttrium barium copper oxide;
Journal_Title :
Applied Superconductivity, IEEE Transactions on
