Fabrication and properties of Nb/Al-AlOx/Nb Josephson junctions for SQUID application

Nb/Al-AlOx/Nb Josephson junctions (JJs) were fabricated using standard photolithography technology at NIM for superconducting quantum interference device (SQUID). The current-voltage (I-V) characteristics of shunted Nb/Al-AlOx/Nb JJs and JJ array were investigated. The critical current density ($J_{c}$) is controlled by exposure time and oxygen pressure during the oxidation process of Al film. It is indicated that the shunted JJs are overdamped and the unshunted JJs are high quality from the I-V curve of JJ array, which are suitable for SQUID application.