Soft X-ray Detection Performance of Superconducting Tunnel Junction Arrays with Asymmetric Tunnel Junction Layer Structure

Abstract

Superconducting tunnel junction (STJ) array detectors with an asymmetric tunnel junction layer structure have been fabricated for the soft X-ray region between 100 eV and 1 keV. The asymmetric layer design was effective in solving the problem of double peak response to monochromatic X-rays, which is commonly observed in STJ detectors. The sensitive area was patterned by a lift-off technique that ensured no contamination on the top Nb electrode surface. The performance of a 100-pixel STJ array detector was investigated through fluorescent X-ray analysis of oxides and nitrides for the energy region of the K-lines of oxygen, nitrogen, and boron. The STJ array detector exhibited a high energy resolution of <15 eV, which cannot be achieved by semiconductor detectors, and an energy nonlinearity of <1%. It was demonstrated that the performance is suitable for fluorescence-yield X-ray absorption fine structure (XAFS) spectroscopy for light trace elements.

Development of an energy‐dispersive X‐ray spectroscopy analyzer employing superconducting tunnel junction array detectors toward nanometer‐scale elemental mapping

“…The performances were insufficient for X‐ray spectroscopy in the SEM. Recently, large‐scale arrays of the STJs have been developed to resolve the above disadvantages, and energy‐dispersive X‐ray detectors based on the STJ array have simultaneously demonstrated excellent energy resolution of less than 10 eV, large detection area of more than 1 mm 2 , and high counting rate capability of about 1 Mcps in the soft X‐ray energy range . Therefore, by using STJ arrays as X‐ray detectors in EDX analyzers, it should be possible to overcome the abovementioned difficulties to realize both the high throughputs of SDDs and the high energy resolution of WDSs.…”

Developments toward the Terahertz Photon Counting System

“…The SIS junctions form parallel-connected twin junctions (PCTJ) and are connected to a twin-slot antenna with a coplanar waveguide, which are designed for 500 GHz. The detector was processed at the CRAVITY facility [2] at National Institute of Advanced Industrial Science and Technology (AIST). Studies to improve the detector performances are in progress; so far a detector with center frequency of 530 GHz has been realized [1].…”