Aluminum thickness dependence of spatial profile in niobium-based superconducting tunnel junctions

Ukibe, Masahiro; Ikeuchi, Takashi; Zama, Tatsuya; Ohkubo, M.

doi:10.1016/j.nima.2003.11.339

Cited by 11 publications

(5 citation statements)

References 7 publications

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“…Superconducting detectors overcome the theoretical limit of semiconductor detectors 15 . Superconducting tunnel junction (STJ) array detectors are suitable for bright SR beams because of an acceptable high flux of over 20 k photons/s per pixel with sufficient Δ E values of 8–15 eV depending on the junction size, junction layer structure, and superconductor materials 13 16 . A group at the Lawrence Livermore National Laboratory pioneered FY–XAFS spectroscopy with STJ detectors 13 .…”

mentioning

confidence: 99%

X-ray absorption near edge spectroscopy with a superconducting detector for nitrogen dopants in SiC

Ohkubo

Shiki

Ukibe

et al. 2012

Sci Rep

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Fluorescence-yield X-ray absorption fine structure (FY-XAFS) is extensively used for investigating atomic-scale local structures around specific elements in functional materials. However, conventional FY-XAFS instruments frequently cannot cover trace light elements, for example dopants in wide gap semiconductors, because of insufficient energy resolution of semiconductor X-ray detectors. Here we introduce a superconducting XAFS (SC-XAFS) apparatus to measure X-ray absorption near-edge structure (XANES) of n-type dopant N atoms (4 ×1019 cm−3) implanted at 500°C into 4H-SiC substrates annealed subsequently. The XANES spectra and ab initio multiple scattering calculations indicate that the N atoms almost completely substitute for the C sites, associated with a possible existence of local CN regions, in the as-implanted state. This is a reason why hot implantation is necessary for dopant activation in ion implantation. The SC-XAFS apparatus may play an important role in improving doping processes for energy-saving wide-gap semiconductors and other functional materials.

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confidence: 99%

X-ray absorption near edge spectroscopy with a superconducting detector for nitrogen dopants in SiC

Ohkubo

Shiki

Ukibe

et al. 2012

Sci Rep

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“…The use of thicker Al layers resulted in the improvement of spatial uniformity and leads to highenergy resolution [5]. In this study, therefore, a detector with relatively thick Al layers of 70 nm was used.…”

Section: Methodsmentioning

confidence: 99%

X-ray absorption spectroscopy of high-k gate dielectric insulating layers for next-generation semiconductor devices as measured by superconducting detectors

Ohkubo

Fons

Kushino

et al. 2006

Nuclear Instruments and Methods in Physics Research Section A:

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“…However, the larger the junction size is, the lower the spectroscopic resolution becomes because of spatial nonuniformity, i.e. the amplitude of the signal that depends on the absorption position of quanta [12], [13]. Therefore, we select a junction size between 100 and 200 μm, depending on the application: for example, 100 μm for high resolution in XAFS and 200 μm for a large sensitive area in MS.…”

Section: Operating Principle Of Stj Detectorsmentioning

confidence: 99%

“…The spatial nonuniformity can be reduced by carefully designing a junction layer structure of Nb/Al/AlO x /Al/Nb [13]. The spatial nonuniformity has been studied experimentally and theoretically [14]- [16].…”

Section: Operating Principle Of Stj Detectorsmentioning

confidence: 99%

Superconducting Tunnel Junction Detectors for Analytical Sciences

Ohkubo

Shiki²,

Ukibe³

et al. 2014

IEEE Trans. Appl. Supercond.

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Superconducting tunnel junction (STJ) detectors exhibit superior detection performance for photons and particles at a high spectroscopic resolution of ∼10 eV, a short dead-time (decay time) of ∼μs, a high quantum efficiency of ∼100%, and a low detection threshold energy of less than 1 eV, which cannot be achieved by conventional detectors. The outstanding detection performance originates from a small superconducting energy gap of ∼meV, which is three orders of magnitude smaller than ∼eV in semiconductors. This paper reports our recent progress in two applications of STJ detectors to fluorescence-yield X-ray absorption fine structure (XAFS) spectrometry for trace light elements in matrices and mass spectrometry (MS) for ions with the same mass/charge-number ratio (m/z) but different charge states and neutral fragments.Index Terms-Mass spectroscopy (MS), superconducting devices, superconducting tunnel junction (STJ), X-ray absorption fine structure (XAFS), X-ray detection. I. INTRODUCTIONS UPERCONDUCTING tunnel junction (STJ) detectors have a sandwich structure of superconductor-insulatorsuperconductor with an insulator thickness of ∼1 nm. The device structure is the same as that of Josephson junctions. For detecting photons or particles, the STJ detectors are operated in the so-called Giaever mode [1], in which the dc Josephson effect is suppressed by applying a small magnetic field of 10-100 G so that the change of quasiparticle tunnel current can be measured. The junctions are biased within the sub-gap region to observe the change of quasiparticle tunnel current.

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Aluminum thickness dependence of spatial profile in niobium-based superconducting tunnel junctions

Cited by 11 publications

References 7 publications

X-ray absorption near edge spectroscopy with a superconducting detector for nitrogen dopants in SiC

X-ray absorption near edge spectroscopy with a superconducting detector for nitrogen dopants in SiC

X-ray absorption spectroscopy of high-k gate dielectric insulating layers for next-generation semiconductor devices as measured by superconducting detectors

Superconducting Tunnel Junction Detectors for Analytical Sciences

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