title: Josephson junctions and DC SQUIDS based on Nb/Al technology.
abstract: A process for fabricating high-quality Josephson junctions and DC SQUIDs on basis of Nb/Al technology has been developed. DC magnetron sputtering is used for the deposition of the metal layers and the barrier is formed by thermal oxidation of the Al-layer. The junction area of 5 microns x 5 microns is obtained using anodisation. Three types of Josephson tunnel junctions have been prepared: standard Nb/Al, AlO kappa/Nb, symmetric Nb/Al, AlO kappa, Al/Nb and Nb/Al, AlO kappa/AlO kappa/Nb, the latter having a double oxide layer. We performed current-voltage and conductance-voltage measurements at different temperatures and special attention was paid to the noise behaviour. Gap and sub-gap parameters as well as barrier parameters are presented. Three different DC SQUID configurations were developed on basis of the Nb/Al Josephson junctions. The measured characteristics of the standard Tesche-Clarke DC SQUID, the resistively shunted SQUID and the inductively shunted SQUID are compared with special attention being paid to the noise properties. A 19-channel DC SQUID magnetometer with standard and/or resistively-shunted DC SQUIDs is under construction.
authors.affiliation: University of Twente, Faculty of Applied Physics, Enschede, The Netherlands.
authors.forename: J
authors.initials: J
authors.lastname: Flokstra
authors.forename: D J
authors.initials: DJ
authors.lastname: Adelerhof
authors.forename: E P
authors.initials: EP
authors.lastname: Houwman
authors.forename: D
authors.initials: D
authors.lastname: Veldhuis
authors.forename: H
authors.initials: H
authors.lastname: Rogalla
mesh_terms: D000535:Aluminum; D004867:Equipment Design; D006801:Humans; D008280:Magnetics; D009556:Niobium
chemical_list: D009556:Niobium; D000535:Aluminum