Hg-based cuprate superconducting films patterned into structures for ultrafast photodetectors

We present results which describe procedures of the preparation and patterning of Hg,Re-Ba-Ca-Cu-O superconducting films suitable for coplanar structures usable as possible photodetectors and for microbridges. We compare structural and electrical properties of the final films from the point of their applicability for photodetectors. Our prepared Re-doped Hg-based films on LaAlO₃ substrate are continuous with a sufficient adhesion to the substrate and with a maximum zero resistance critical temperature T_C0 ∼ 122 K. The X-ray diffraction of all the films confirmed the Hg-1212 phase beside the minor Hg-1223 phase and intergrowth phases in some cases. In spite of epitaxial character of the final Hg-based films, the microwave and magnetic measurements suggest a possible existence of nonstoichiometric material between the grains which we register as a presence of weak links near the transition into the superconducting state. We show some electrical properties of the prepared superconducting structures, too. The prepared coplanar structures show ultrafast photoresponse signal to incident laser pulse.