A. Matsumura et al., X-RAY-DETECTION WITH NB ALOX/NB SUPERCONDUCTING TUNNEL-JUNCTIONS AND ENERGY DIFFUSION EFFECT ON ENERGY RESOLUTION/, Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment, 329(1-2), 1993, pp. 227-237
Nb/AlOx/Nb superconducting tunnel junctions with low leakage current w
ere fabricated. The ultra low leakage current was maintained after 100
thermal cycles. X-rays were detected with three sizes of junctions on
several wafers. The pulse height spectra show the improvement of ener
gy resolution with the increase in junction area. Using the diffusion
length of excited electrons in the superconductor, the effect of dispe
rsion of excited electron from the junction area to the electric lead
and trap of excited electrons at the film edge (energy diffusion effec
t) was evaluated. Calculated results explain the characteristics of th
e experimental results. It is concluded that a large junction area is
desirable to reduce the energy diffusion effect on the energy resoluti
on.