Thin-film persistent current switch

• Published in: IEEE transactions on applied superconductivity Vol. 15; no. 3; pp. 3821 - 3826
• Main Authors: Balchandani, P., Torii, R.H., Shile, R.
• Format: Journal Article
• Language: English
• Published: New York, NY IEEE 01.09.2005; Institute of Electrical and Electronics Engineers; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Applied sciences; Critical current density; Current injection; current switch; Electronics; Exact sciences and technology; heat switch; Heat switches; Heating; Niobium; Persistent currents; Resistors; Semiconductor electronics. Microelectronics. Optoelectronics. Solid state devices; Sputtering; Superconducting devices; Superconducting films; Superconducting thin films; Superconductivity; Switches; Switching; Thermal conductivity; thin film; Thin films; Three dimensional models; Transistors; Thermal characteristic; Waveform; Critical current density; Current commutator; Current injection; Sputtering; Thin film; Superconducting materials; Microelectronic fabrication; Three dimensional model; Experimental result; Switching conditions; Response time; Thermal conductivity; Switching circuit; Thermal model; current switch; Joule effect; heat switch
• ISSN: 1051-8223; 1558-2515
• DOI: 10.1109/TASC.2005.847491

We have developed a fast, low power heat switch for switching a niobium thin film between the normal and superconducting state. The sputtered niobium film (400 nm thick, 100 /spl mu/m wide) has a critical current density of 5/spl times/10/sup 10/ Am/sup -2/. Switching is produced by joule heating a small section of the niobium film with a titanium thin-film resistor. With the heat switch in vacuum, the minimum heater power needed to switch to the normal state was 4.5/spl times/10/sup -5/ W. A simple three-dimensional thermal model shows that the minimum power is primarily determined by the thermal conductivity of the substrate. We have achieved response times less than 10/sup -6/ s.