Fabrication of superconducting tunnel junctions for soft X‐ray spectroscopy |
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| Authors: | M Ukibe S Shiki Y Kitajima M Ohkubo |
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| Institution: | 1. Research Institute of Instrumentation Frontier, National Institute of Advanced Industrial Science and Technology, 1‐1‐1, Umezono, Tsukuba, Ibaraki 305‐8568, Japan;2. Photon Factory, Institute of Materials Structure Science, High Energy Accelerator Research Organization, 1‐1, Oho, Tsukuba, Ibaraki 305‐0801, Japan |
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| Abstract: | Superconducting tunnel junction (STJ) array detectors with a new design, which has a minimum junction edge coverage of an SiO2 insulation, passivation layer and an asymmetric tunnel junction layer structure, have been fabricated for a soft X‐ray region between 100 eV and 1 keV. The sensitive area was patterned by removing the SiO2 deposition layer by a lift‐off technique that ensured no contamination layer on the top Nb electrode surface. The width of the passivation rim was as narrow as 0.5 µm at the junction edge. The clean Nb surface and the narrow SiO2 rim resulted in almost no artifact photon events in a low‐energy region. The asymmetric layer design is effective in solving a problem of double peak response to monochromatic X‐rays, which is commonly observed in STJ detectors. The performance of a 100 pixel array detector was investigated by the fluorescent X‐ray analysis of oxides and nitrides: an energy resolution of about 30 eV for the total absorption of the Kα lines of oxygen and nitrogen. We plan to realize an energy resolution of better than 20 eV and a counting rate of over 1 Mcps for fluorescence‐yield X‐ray absorption spectroscopy for light trace elements. Copyright © 2011 John Wiley & Sons, Ltd. |
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