Current-voltage characteristics of 100-pixel 200-μm-square superconducting tunnel junction X-ray detector array

The superconducting tunnel junction (STJ) X-ray detector is an important tool for materials analysis because of its high energy resolution and high counting rate. In this work, the current-voltage (I-V) characteristics were investigated for a 100-pixel STJ array with a pixel size of 200 μm having a layer structure of Nb-Al/AlO _x /Al-Nb and working at 0.3 K. The fabrication yield of the 200-μm STJ reached approximately 90%. A series of I-V curves for a single pixel in different cooling runs showed a discrete excess current, possibly due to the trapping of single fluxoids. With a reduction of the ambient magnetic field during cooling, larger STJ pixels can be used.