I-V characteristics of NbN-NbN Josephson point contacts

Current--voltage characteristics of NbN--NbN Josephson point contacts have been examined. The point contacts were formed by NbN thin films deposited on Nb or tungsten whiskers and Nb posts. The current--voltage characteristics of those contacts were investigated with and without irradiation of microwaves and far-infrared light. High values of the I sub c R sub n product and the energy gap structure were observed, which corresponded to the high-energy gap of NbN. Shapiro steps for far-infrared light up to 170 mu m were observed and the possibility of replacing Nb Josephson point contacts with NbN ones is indicated. Graphs. 7 ref.--AA