Asymmetric response of superconducting niobium-tunnel-junction x-ray detectors

Journal Article · Tue Oct 01 04:00:00 EDT 1996 · Physical Review, B: Condensed Matter

DOI:https://doi.org/10.1103/PhysRevB.54.9484· OSTI ID:383850

Ohkubo, M ^[1]; Martin, J; Drachsler, K; Gross, R; Huebener, R P ^[2]; Sakamoto, I; Hayashi, N ^[3]

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1. Forschungszentrum Karlsruhe, Institut fuer Nukleare Festkoerperphysik, Postfach 3640, D-76021, Karlsruhe (Germany)
2. Physikalisches Institut, Lehrstuhl Experimentalphysik II, Universitaet Tuebingen, Morgenstelle 14, D-72076 Tuebingen (Germany)
3. Electrotechnical Laboratory, Umezono, Tsukuba, Ibaraki, 305 (Japan)

The asymmetric response of the counter and base electrodes of x-ray detectors employing polycrystalline niobium tunnel junctions has been studied by low-temperature scanning electron microscopy (LTSEM). LTSEM has revealed that the base electrode produces a signal more than two times larger than the counter electrode, and effective quasiparticle lifetimes are 100 ns in the counter and 280 ns in the base. Based on the {ital I}-{ital V} characteristics and the measured effective quasiparticle lifetimes, we propose a model structure for a spatial variation of the gap parameter {Delta}, which involves proximity quasiparticle trapping layers. The small counter signal is caused by the shorter quasiparticle lifetime and the trapping effect. The LTSEM results are consistent with x-ray spectra for a radioactive {sup 55}Fe source. {copyright} {ital 1996 The American Physical Society.}

• OSTI ID: 383850
• Journal Information: Physical Review, B: Condensed Matter, Journal Name: Physical Review, B: Condensed Matter Journal Issue: 13 Vol. 54; ISSN PRBMDO; ISSN 0163-1829
• Country of Publication: United States
• Language: English

Related Subjects

66 PHYSICS
COOPER PAIRS
ENERGY GAP
LIFETIME
NIOBIUM
QUASI PARTICLES
RADIATION DETECTORS
RESPONSE FUNCTIONS
SUPERCONDUCTING JUNCTIONS
TUNNEL EFFECT
X-RAY DETECTION