Fabrication of superconducting bilayer transition edge thermometers and their application for spaceborne X-ray microcalorimetry

Finkbeiner, F. M.; Chen, T.C.; Aslam, Shahid; Figueroa‐Feliciano, E.; Kelley, R. L.; Li, M.; Mott, D. B.; Stahle, C. K.; Stahle, C. M.

doi:10.1109/77.783646

Cited by 23 publications

(22 citation statements)

References 7 publications

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“…This parameter has been notoriously difficult to control, see for example references 1,13 . In our current setup, operational constraints require a minimum 10 minute interrupt before deposition of the Cu layer can commence after the deposition of the Mo layer is completed.…”

Section: Mo/cu Bilayersmentioning

confidence: 99%

“…Two techniques are in common use for the deposition of high quality bilayers: a) e-beam evaporation onto heated substrates for Mo/Au 1 , and b) sputter deposition at room temperature for Mo/Cu 2,3,4,5 . While in principle the bilayer fabrication should be straightforward, in practice reproducibility remains a significant challenge, partly because the interactions of various process and materials parameters are poorly understood.…”

Section: Introductionmentioning

confidence: 99%

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Fabrication of Superconducting Mo/Cu Bilayers Using Ion-Beam-Assisted e-Beam Evaporation

et al. 2016

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Superconducting/normal metal bilayers with tunable transition temperature are a critical ingredient to the fabrication of high performance transition edge-sensors (TES). Popular material choices include Mo/Au and Mo/Cu, which exhibit good environmental stability and provide low resistivity films to achieve adequate thermal conductivity. The deposition of high quality Mo films requires sufficient adatom mobility, which can be provided by energetic ions in sputter deposition, or by heating the substrate in an e-beam evaporation process. The bilayer Tc depends sensitively on the exact deposition conditions of the Mo layer and the superconducting/normal metal interface. Because the individual contributions (strain, crystalline structure, contamination) are difficult to disentangle and control, reproducibility remains a challenge. Recently, we have demonstrated that low energy ion beam assist during e-beam evaporation offers an alternative route to reliably produce high quality Mo films without the use of substrate heating. The energy and momentum delivered by the ion beam provides an additional control knob to tune film properties such as resistivity and stress. In this report we describe modifications made to the commercial end-Hall ion-source to avoid iron contamination allowing us to produce superconducting Mo films. We show that the ion beam is effective at enhancing the bilayer interface transparency and that bilayers can be further tuned to reduced Tc and higher conductivity by vacuum annealing.

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Section: Mo/cu Bilayersmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Fabrication of Superconducting Mo/Cu Bilayers Using Ion-Beam-Assisted e-Beam Evaporation

et al. 2016

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“…The superconducting layer must then be a superconductor with T c greater than 100 mK and less than roughly 2 K, and both chemically and thermally compatible with the noble metals. Of the possible choices, we felt that Mo [9] was the most promising. Molybdenum is widely used in semiconductor and superconductor fabrication processes; it is essentially insoluble with the noble metals [10] and has a very low rate of oxide formation.…”

Section: Bilayer Developmentmentioning

confidence: 99%

Microfabricated transition-edge X-ray detectors

Hilton

Martinis

Irwin

et al. 2001

IEEE Trans. Appl. Supercond.

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We are developing high performance x-ray detectors based on superconducting transition-edge sensors (TES) for application in materials analysis and astronomy. Using our recently developed fully lithographic TES fabrication process, we have made devices with an energy resolution of 4.5 ¦0.1 eV for 5.9 keV x-rays, the best reported energy resolution for any energy dispersive detectors in this energy range. These detectors utilize micromachined thermal isolation structures and transitionedge sensors fabricated from Mo/Cu bilayers with normal-metal boundary conditions. We have found the normal-metal boundary conditions to be critical to stable and reproducible low noise operation. In this paper we present details of fabrication and performance of these devices.

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“…Currently, our state-of-the-art microcalorimeter is a superconducting transition-edge sensor (TES) made of a Mo/Au bilayer [4,5] attached to a 300 µm-wide overhanging absorber made of Au (1.5 µm) and Bi (3 µm), designed for the soft x-ray band (0.1-12 keV). For a mission consisting of a kilopixel array of these devices, plus an extended outer array of larger pixels, the entire microcalorimeter assembly would be approximately 3.1 cm on a side.…”

Section: Motivationmentioning

confidence: 99%

Development of a TES-Based Anti-coincidence Detector for Future x-Ray Observatories

et al. 2012

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1: Development of a TES-based anti-coincidence detector for future x-ray observatories Microcalorimeters onboard future x-ray observatories require an anti-coincidence detector to remove environmental backgrounds. In order to most effectively integrate this anticoincidence detector with the main microcalorimeter array, both instruments should use similar read-out technology. The detectors used in the Cryogenic Dark Matter Search (CDMS) use a phonon measurement technique that is well suited for an anti-coincidence detector with a microcalorimeter array using SQUID readout. This technique works by using a transition-edge sensor (TES) connected to superconducting collection fins to measure the athermal phonon signal produced when an event occurs in the substrate crystal. Energy from the event propagates through the crystal to the superconducting collection fins, creating quasiparticles, which are then trapped as they enter the TES where they produce a signal. We are currently developing a prototype anti-coincidence detector for future x-ray missions and have recently fabricated test devices with MolAu TESs and Al collection fins. We will present results from the first tests of these devices which indicate a proof of concept that quasiparticle trapping is occurring in these materials.

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Fabrication of superconducting bilayer transition edge thermometers and their application for spaceborne X-ray microcalorimetry

Cited by 23 publications

References 7 publications

Fabrication of Superconducting Mo/Cu Bilayers Using Ion-Beam-Assisted e-Beam Evaporation

Fabrication of Superconducting Mo/Cu Bilayers Using Ion-Beam-Assisted e-Beam Evaporation

Microfabricated transition-edge X-ray detectors

Development of a TES-Based Anti-coincidence Detector for Future x-Ray Observatories

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