Josephson effect and macroscopic quantum interference in high-T _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 SrTiO₃ and LiNbO₃ substrates by laser sputtering of ceramic targets. Values of critical current I_c and normal resistance R_n of the weak links could be altered by plasma etching of the structures. I_cR _n products up to 100 μV 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