INVESTIGATION OF EPITAXIAL NIOBIUM BASED SUPERCONDUCTING TUNNEL JUNCTION DETECTORS

Superconducting Nb/Al-AlO(x)/Nb tunnel junctions (STJs) with epitaxial niobium base electrode are investigated as weak x-ray detectors. The recorded x-ray spectra show a two peak structure that is attributed to the absorption of 6 keV x-rays in the two junction electrodes. Low Te mperature Scanning Electron Microscopy (LTSEM) proves, that the high c harge output peak of the x-ray spectra is associated with x-rays absor bed in the epitaxial niobium film. The significantly reduced charge ou tput for events in the polycrystalline niobium electrode is found to b e bias voltage dependent.