High-performance (Hg, Re)Ba2CaCu2Oy grain-boundary Josephson junctions and dc superconducting quantum interference devices

High-performance grain-boundary Josephson junctions and dc superconducting quantum interference devices (SQUIDs) have been fabricated using c-axis oriented ${\mathrm{(Hg,\hspace{0.17em}Re)Ba}}_{\mathrm{2}}{\mathrm{CaCu}}_{\mathrm{2}}{\mathrm{O}}_y$ thin films grown on bicrystal ${\mathrm{SrTiO}}_{\mathrm{3}}$ substrates with a 24° misorientation angle. The junctions exhibit supercurrent up to a temperature close to the film $T_c$ and resistively shunted junctionlike current–voltage characteristics. A rather high $I_c{R}_n$ product of 400–460 μV is observed at 77 K in some junctions. The dc SQUIDs show a field-induced periodic voltage up to 111 K. They also exhibit a voltage modulation depth as large as 90, 27, and 1–2 μV at 77, 97, and 111 K, respectively.