Etching suspended superconducting tunnel junctions from a multilayer

Nguyễn, Hồng Quang; Pascal, Laetitia; Peng, Zhihui; Buisson, Olivier; Gilles, B.; Winkelmann, Clemens; Courtois, Hervé

doi:10.1063/1.4729779

Cited by 18 publications

(21 citation statements)

References 18 publications

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“…In accord with previous work [18,21], our series of experiments [30,31] proves that the S-I-N-I-S cooler reaches lower temperature with a better thermalized superconductor using a "passive" quasiparticle trap. Although the enhancement is impressive, the cooler does not meet theoretical expectations with this method only.…”

Section: Discussionsupporting

confidence: 91%

“…The metals are wet etched as in Ref. [30]. A third photolithography and Cu wet etch define the N-I-S junctions with the size of the main cooler of 50 × 4 μm 2 .…”

Section: Resultsmentioning

confidence: 99%

“…1, and prove that the double-stage N-I-S refrigerator performance is significantly improved. Based on an established technique [30], a powerful large-junction S-I-N-I-S cooler (two N-I-S junctions back to back) is fabricated with a well-thermalized superconductor of aluminum boosted by an advanced quasiparticle-trapping strategy. A normal-metal layer is engineered directly underneath the hot superconductor to improve thermalization.…”

Section: Introductionmentioning

confidence: 99%

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Cascade Electronic Refrigerator Using Superconducting Tunnel Junctions

et al. 2016

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Microrefrigerators that operate in the subkelvin regime are key devices in quantum technology. A wellstudied candidate, an electronic cooler using normal-metal-insulator-superconductor (N-I-S) tunnel junctions, offers substantial performance and power. However, its superconducting electrodes are severely overheated due to exponential suppression of their thermal conductance towards low temperatures, and the cooler performs unsatisfactorily-especially in powerful devices needed for practical applications. We employ a second N-I-S cooling stage to thermalize the hot superconductor at the backside of the main N-I-S cooler. Not only providing a lower bath temperature, the second-stage cooler actively evacuates quasiparticles out of the hot superconductor, especially in the low-temperature limit. We demonstrate the apparent advantage of our approach. This cascade design can also be employed to manage excess heat in other cryoelectronic devices.

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Section: Discussionsupporting

confidence: 91%

“…The metals are wet etched as in Ref. [30]. A third photolithography and Cu wet etch define the N-I-S junctions with the size of the main cooler of 50 × 4 μm 2 .…”

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Cascade Electronic Refrigerator Using Superconducting Tunnel Junctions

et al. 2016

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“…11 Recently, we have developed a SINIS electron cooler with a well thermalized superconductor using photolithography and wet etching. 24,25 This device has enough power to handle an external load, yet it performs outstandingly over a wide range of temperature. 26 In this paper, we demonstrate an integration of these coolers on a SiN membrane.…”

mentioning

confidence: 99%

A robust platform cooled by superconducting electronic refrigerators

Nguyễn

Meschke

Pekola

2015

Applied Physics Letters

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A biased tunnel junction between a superconductor and a normal metal can cool the latter electrode. Based on a recently developed cooler with high power and superior performance, we have successfully integrated it with a dielectric silicon nitride membrane, and cooled phonons from 305 mK down to 200 mK. Without perforation and covered under a thin alumina layer, the membrane is rigorously transformed into a cooling platform that is robust and versatile for multiple practical purposes. We discuss our results and possibilities to further improve the device.Comment: 4 pages, 3 figure

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“…Finally, we mention the successful chemical etching of a 100 nm thick aluminum layer under a 100 nm thick layer of Cu. 9 A bolometer composed of a Nb-AlO x -Nb SIS tunnel junction as a thermometer thermally coupled to the suspended resistive element was realized in Ref. 10.…”

mentioning

confidence: 99%

Electrical and optical properties of a bolometer with a suspended absorber and tunneling-current thermometers

Tarasov

Édelman

Mahashabde

et al. 2017

Applied Physics Letters

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We have developed a bolometer with a suspended normal-metal absorber connected to superconducting leads via tunneling barriers. Such an absorber has reduced heat losses to the substrate, which greatly increases the responsivity of the bolometer to over 10 9 V/W at 75 mK when measured by dc Joule heating of the absorber. For high-frequency experiments, the bolometers have been integrated in planar twin-slot and log-periodic antennas. At 300 GHz and 100 mK, the bolometer demonstrates the voltage and current response of 3 Â 10 8 V/W and 1.1 Â 10 4 A/W, respectively, corresponding to the quantum efficiency of $15 electrons per photon. An effective thermalization of electrons in the absorber favors the high quantum efficiency. We also report on how the in-plane-and transverse magnetic fields influence the device characteristics. In superconducting bolometers, the electromagnetic radiation increases the temperature T e of the electron system in a normal-metal (N) absorber. Superconducting (S) leads connected to the absorber through insulating barriers (I) form tunneling junctions. The tunneling current across such a junction is a strong function of T e , which thereby offers a sensitive readout of the radiation power. At the low bath temperature T, the absorbed photon energy hf ) k B T is distributed among quasiparticles through their multiple interactions and is eventually lost into the cold bath through electrical contacts and a substrate. Here, h is the Planck constant, f is the frequency of incident radiation, and k B is the Boltzmann constant. The balance between the radiation-and cooling-powers determines T e . Decoupling the absorber from the heat sinks would increase T e and the detector response through the multiplication of excited electrons. It should be remembered that for the photon energy hf ) k B T e , the energy distribution of electrons can be substantially different from the Fermi distribution, depending on the quasiparticle interactions and tunneling rate of the excited electrons through the SIN junction. For estimations of bolometric sensitivity, it is usually assumed that the absorbed radiation is equivalent to dc Joule heating of the same power.Heat loss from an absorber can be reduced by fabricating the absorber on, e.g., a silicon nitride membrane supported by metallic thin-film beams having a small thermal conductance.1 Also, the effective thermal capacity of absorbers fabricated on a membrane is smaller than for absorbers on a bulk substrate.2 Further improvements can be achieved if an absorber is suspended without any supporting membrane. For an electron that absorbs a 300 GHz photon, the electron-phonon and electron-electron scattering times are about 0.2 ns and 1 ns, respectively. The excited electron creates a high-energy phonon that can easily escape from the absorber if the absorber sits on a substrate or is connected to electrodes of the same material.3 Using different materials for the absorber and electrodes can further improve thermal insulation due to a high acoustic-impedance mism...

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Etching suspended superconducting tunnel junctions from a multilayer

Cited by 18 publications

References 18 publications

Cascade Electronic Refrigerator Using Superconducting Tunnel Junctions

Cascade Electronic Refrigerator Using Superconducting Tunnel Junctions

A robust platform cooled by superconducting electronic refrigerators

Electrical and optical properties of a bolometer with a suspended absorber and tunneling-current thermometers

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