Suppression of magnetic flux trapping by moats formed in NbN ground planes

Abstract

We have investigated the effect of moats in NbN ground planes on magnetic flux trapping by using series arrays of 1000 Josephson junctions fabricated on Nb and NbN ground planes. The junctions on the NbN ground plane exhibited no trapping for external magnetic fields in the range of -2.2 to 1.2 μT, which was twice the range over which no flux trapping occurred for junctions on the Nb ground plane. This advantage of the NbN ground plane can be explained using a Bean-Livingston model with a longer penetration depth and higher critical temperature of NbN than those of Nb. © 2011 The Japan Society of Applied Physics.