Abstract
This paper describes a new type of thin film Superconducting Quantum Interference Devices, (SQUID). SQUID is a very sensitive magnetic sensor whose principle of operation is based on the magnetic flux quantization and the Josephson effects.
After a brief summary of SQUID operation, the construction and properties of Nb thin film SQUID are dealt with in some detail. This includes the production process and sensitivity estimates.
An Nb thin film is deposited by rf-sputtering on a flat substrate and a microbridge is fabricated with photolithography, sputter-etching and oxidization techniques. This structure is suitable for massproduction and has an excellent mechanical stability. Several SQUID stored at room temperature for three years during which they were periodically subjected too liquid-helium temperature more than 50 times showed no significant deterioration.
The last part of this report covers the original technique used to lower SQUID ring inductance and hence increase sensivity to obtain a resolution better than 4×10-19Wb/√Hz.
