SWITCHING DYNAMICS OF NB ALOX/NB JOSEPHSON-JUNCTIONS - MEASUREMENTS FOR AN EXPERIMENT OF MACROSCOPIC QUANTUM COHERENCE/

Josephson junctions based on Nb/AlOx/Nb trilayer technology have demon strated excellent quality, exhibiting very low dissipation in the subg ap region. This property is very important for all those experiments w hich have to deal with the quantum behavior of macroscopic variables i n Josephson devices. In view of performing an experiment of macroscopi c quantum coherence with a Josephson device, we measured the escape te mperature and the return current of several junctions fabricated with different processes and having different characteristics, by cooling t hem from 4.2 to 0.3 K. We show that, for what concerns the process of escape from the zero-voltage state, no difference can be found among d ifferent junctions. On the other hand, the dissipation properties are strongly influenced by the current density, with lower current density resulting in lower intrinsic dissipation. (C) 1996 American Institute of Physics.