THERMAL-STABILITY OF SIS TUNNEL JUNCTION WITH SILICON BARRIER

The thermal treatment of Nb/Si/Nb Josephson junction with high resisti ve amorphous silicon barrier (2nm thick) involves the interdiffusion a t Nb/Si interfaces even at 250 degrees C. In order to study these tiny interdiffusion process a superlattice [Nb(6nm)/Si(2nm)]10 (prepared at the same technological conditions as the Josephson junction) nas us ed for low angle x-ray spectroscopy. The interdiffusion yielding a sub layer of superconducting Nb-Si amorphous mixture at the interfaces was detected. This represents in the Josephson junction the decrease of S i-barrier thickness and consequently the increase of critical current in measured I-V characteristic.