JOSEPHSON-JUNCTIONS AND DC-SQUIDS BASED ON NB AL TECHNOLOGY/

A process for fabricating high-quality Josephson junctions and DC SQUI Ds on basis of Nb/Al technology has been developed. DC magnetron sputt ering is used for the deposition of the metal layers and the barrier i s formed by thermal oxidation of the Al-layer. The junction area of 5- mu-m x 5-mu-m is obtained using anodisation. Three types of Josephson tunnel junctions have been prepared: standard Nb/Al, AlOx/Nb, symmetri c Nb/Al, AlOx, Al/Nb and Nb/Al, AlOx/AlOx/Nb, the latter having a doub le oxide layer. We performed current-voltage and conductance-voltage m easurements at different temperatures and special attention was paid t o the noise behaviour. Gap and sub-gap parameters as well as barrier p arameters are presented. Three different DC SQUID configurations were developed on basis of the Nb/Al Josephson junctions. The measured char acteristics of the standard Tesche-Clarke DC SQUID, the resistively sh unted SQUID and the inductively shunted SQUID are compared with specia l attention being paid to the noise properties. A 19-channel DC SQUID magnetometer with standard and/or resistively-shunted DC SQUIDs is und er construction.