Josephson effect and macroscopic quantum interference in high-T/sub c/ superconducting thin-film weak links at 77 K

The authors studied the properties of single and double superconducting weak links (Dayem microbridges) fabricated by direct photolithography from thin films of 1-2-3 copper oxides, deposited on SrTiO/sub 3/ and LiNbO/sub 3/ substrates by laser sputtering of ceramic targets. Values of critical current I/sub c/ and normal resistance R/sub n/ of the weak links could be altered by plasma etching of the structures. I/sub c/R/sub n/ products up to 100 mu V were achieved, and well-pronounced Shapiro steps under 8-GHz microwave radiation were observed at 77 K. Macroscopic quantum interference was clearly registered in double microbridge structures at the same temperature