Temperature sensitivity and noise of an HTSC Josephson detector on a sapphire bicrystal substrate at 77 K

Abstract

In YBa 2 Cu 3 O 7 ‐ x films grown on sapphire bicrystal substrates, the Josephson junctions are prepared based on artificial grain boundaries formed by the turn of the crystal lattices about the [100] axis. The films are deposited by the laser ablation method on the buffer CeO 2 layer. The critical film temperature reaches 88.5 K at a transition width of 1.5 K. Junctions from 2 to 3- µ m wide are integrated into the planar log-periodic antennas and their characteristics are measured at 77 K. The characteristic voltage I c R n reaches 570 µ V. With exposure to external radiation at a frequency of 113 GHz, the Shapiro steps were observed on the current‐voltage characteristic. The temperature sensitivity of this detector placed in a quasi-optical receiving unit is measured. At the modulation of the input radiation temperature 77 K/300 K, a response of more than 200 nV is observed at the detector output. At the modulation frequency, intrinsic noise is about 1 nV/Hz 1/2 , which corresponds to a temperature resolution of 1 K.