| 摘要 |
PURPOSE:To constitute both upper and lower electrodes by a hard superconductive body and to provide excellent leak current characteristics, by using Nb for a lower electrode film, using NbN including 40-60 at % N for an upper electrode film and using an Al oxide for a tunnel barrier layer. CONSTITUTION:A Josephson junction, in which Nb is used for a lower electrode, an Al oxide is used for a tunnel barrier layer and NbN is used for an upper electrode, is prepared. In this case, a silicon wafer 1 is provided on a substrate holder in a vacuum device, and an Nb film 2 is deposited to a thickness of 200nm. Then, an Al film is deposited on the Nb film to a thickness of 4nm from an Al target. O2 gas of 100Pa is introduced, and the surface of the Al film is exposed to the O2 gas for several minutes. Thus an Al oxide 3 is formed. Then Ar gas and N2 gas are simultaneously introduced, and the Nb is sputtered. Thus an NbN film 4 having the thickness of 100nm is deposited. A junction part and a resist pattern including the wiring of the Nb film 2 at the lower electrode is formed. The Nb2, the Al oxide 3 and the NbN film 4 are etched by an ion etching method. Thus the resist pattern corresponding to the junction part is formed. |
