Nanostructuring YBCO thin films by heavy-ion beam for local magnetic field and infrared photon detection

Abstract

We report about the functional exploiting of the High-Energy Heavy-Ion (HEHI) lithography aimed at modulating in confined regions both structural and electrical properties of high temperature superconducting YBa 2Cu 3O 7− x (YBCO) films. We discuss the physical behaviors related to the HEHI modification of such films by means of 3D columnar defects, exhibiting nanometric cross section. A major part of this paper is devoted to the viability of well-defined (B,T,J) phase-diagram zones, where electrical decoupling between as-grown and modified parts occurs and so guarantees external-signal localization. In order to stress out complementary behaviors into different phase-diagram regions of locally modified YBCO films, we present low-temperature magnetic imaging, accounting for the case where a spatially continuous Meissner state holds on throughout the whole sample. In this case, the continuity of the Meissner state hampers localization of dissipative signals in the nanostructured region. On the contrary, inside the (B,T,J) phase-diagram zones belonging to the temperature range where the Meissner state is spatially broken, the temperature range of dissipation confinement under external stimuli can be functionally exploited. Then the main target of a road map pointing towards position-sensitive infrared superconducting sensors is enlightened by means of crucial experimental results. With this respect, a device layout, consisting into HEHI modified YBCO film grown either on YSZ or MgO substrates, is chosen to test the functional behavior of infrared detectors working above liquid nitrogen temperature and, in the case of MgO substrate, displaying sub-millisecond response-time.