Browsing by Author "Meschke, M."
Now showing 1 - 20 of 33
Results Per Page
Sort Options
Item Cascade Electronic Refrigerator Using Superconducting Tunnel Junctions(2016-11-23) Nguyen, Hung; Peltonen, Joonas; Meschke, M.; Pekola, J. P.; Department of Applied PhysicsMicrorefrigerators that operate in the subkelvin regime are key devices in quantum technology. A well-studied 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.Item Double oxidation scheme for tunnel junction fabrication(American Vacuum Society, 2008) Holmqvist, T.; Meschke, M.; Pekola, Jukka P.; Department of Applied Physics; Teknillisen fysiikan laitos; Perustieteiden korkeakoulu; School of ScienceThe authors report a method to achieve Al–AlOx–Al tunnel junctions with high specific resistance in a controlled manner using a double oxidation technique. The technique is based on the standard method for oxidation repeated on an additional Al layer. The tunnel junctions were characterized with standard methods, such as comparison of room temperature resistance with liquid helium resistance and the authors found them to be of comparable quality to junctions fabricated with standard single oxidation. Fitting with the Simmons model suggests that both the barrier width and barrier height are consistent with those obtained in a single oxidation step. The junction specific capacitance was determined at low temperature to be 68fF/μm2. These junctions, employed in low temperature measurements and applications, demonstrate expected and stable conductance characteristics. The double oxidation method is straightforward to implement in a basic setup for tunnel junction fabrication.Item Electronic cooling of a submicron-sized metallic beam(AIP Publishing, 2009) Muhonen, J. T.; Niskanen, A. O.; Meschke, M.; Pashkin, Yu. A.; Tsai, J. S.; Sainiemi, L.; Franssila, S.; Pekola, Jukka P.; Department of Applied Physics; Teknillisen fysiikan laitos; Perustieteiden korkeakoulu; School of ScienceWe demonstrate electronic cooling of a suspended AuPd island using superconductor-insulator-normal metaltunnel junctions. This was achieved by developing a simple fabrication method for reliably releasing narrow submicron-sized metal beams. The process is based on reactive ion etching and uses a conducting substrate to avoid charge-up damage and is compatible with, e.g., conventional e-beam lithography, shadow-angle metal deposition, and oxide tunnel junctions. The devices function well and exhibit clear cooling, up to a factor of 2 at sub-Kelvin temperatures.Item Erratum(2014-10-06) Najafi Jabdaraghi, Robab; Meschke, M.; Pekola, J. P.; O.V.Lounasmaa-laboratorioApplied Physics Letters 105(14), 149903, DOI: http://doi.org/10.1063/1.4897989. Original article: Applied Physics Letters 104, 082601 (2014)Item Erratum: “Non-hysteretic superconducting quantum interference proximity transistor with enhanced responsivity”(AIP Publishing, 2014) Jabdaraghi, R. N.; Meschke, M.; Pekola, Jukka P.; Department of Applied Physics; Teknillisen fysiikan laitos; Perustieteiden korkeakoulu; School of ScienceItem Ex situ tunnel junction process technique characterized by Coulomb blockade thermometry(American Vacuum Society, 2010) Prunnila, M.; Meschke, M.; Gunnarsson, D.; Enouz-Vedrenne, S.; Kivioja, J. M.; Pekola, Jukka P.; Department of Applied Physics; Teknillisen fysiikan laitos; Perustieteiden korkeakoulu; School of ScienceThe authors investigate a wafer scale tunnel junction fabrication method, where a plasmaetched via through a dielectric layer covering bottom Alelectrode defines the tunnel junction area. The ex situ tunnel barrier is formed by oxidation of the bottom electrode in the junction area. Room temperature resistance mapping over a 150 mm wafer gives local deviation values of the tunnel junction resistance that fall below 7.5% with an average of 1.3%. The deviation is further investigated by sub-1 K measurements of a device, which has one tunnel junction connected to four arrays consisting of Njunctions (N=41, junction diameter 700 nm). The differential conductance is measured in single-junction and array Coulomb blockade thermometer operation modes. By fitting the experimental data to the theoretical models, the authors found an upper limit for the local tunnel junction resistance deviation of ∼5% for the array of 2N+1junctions. This value is of the same order as the minimum detectable deviation defined by the accuracy of the authors’ experimental setup.Item Fast Electron Thermometry for Ultrasensitive Calorimetric Detection(2015) Gasparinetti, S.; Viisanen, Klaara; Saira, Olli-Pentti; Faivre, T.; Arzeo, M.; Meschke, M.; Pekola, J.P.; Quantum Phenomena and Devices; Department of Applied PhysicsWe demonstrate radio-frequency thermometry on a micrometer-sized metallic island below 100 mK. Our device is based on a normal-metal–insulator–superconductor tunnel junction coupled to a resonator with transmission readout. In the first generation of the device, we achieve 90 μK/√Hz noise-equivalent temperature with 10 MHz bandwidth. We measure the thermal relaxation time of the electron gas in the island, which we find to be of the order of 100 μs. Such a calorimetric detector, upon optimization, can be seamlessly integrated into superconducting circuits, with immediate applications in quantum-thermodynamics experiments down to single quanta of energy.Item Laterally proximized aluminum tunnel junctions(AIP Publishing, 2011) Koski, J. V.; Peltonen, J. T.; Meschke, M.; Pekola, Jukka P.; Department of Applied Physics; Teknillisen fysiikan laitos; Perustieteiden korkeakoulu; School of ScienceThis letter presents experiments on junctions fabricated by a technique that enables the use of high-quality aluminum oxide tunnel barriers with normal metal electrodes at low temperatures. Inverse proximity effect is applied to diminish the superconductivity of an aluminum dot through a clean lateral connection to a normal metal electrode. To demonstrate the effectiveness of this method, fully normal-state single electron transistors (SETs) and normal metal-insulator-superconductor (NIS) junctions applying proximized Aljunctions were fabricated. The transport characteristics of the junctions were similar to those obtained from standard theoreticalmodels of regular SETs and NIS junctions.Item Magnetic-field-induced stabilization of nonequilibrium superconductivity in a normal-metal/insulator/superconductor junction(American Physical Society (APS), 2011) Peltonen, J. T.; Muhonen, J. T.; Meschke, M.; Kopnin, N. B.; Pekola, Jukka P.; Department of Applied Physics; Teknillisen fysiikan laitos; Perustieteiden korkeakoulu; School of ScienceA small magnetic field is found to enhance relaxation processes in a superconductor, thus stabilizing superconductivity in nonequilibrium conditions. In a normal-metal (N)/insulator/superconductor (S) tunnel junction, applying a field of the order of 100μT leads to significantly improved cooling of the N island by quasiparticle (QP) tunneling. These findings are attributed to faster QP relaxation within the S electrodes as a result of enhanced QP drain through regions with a locally suppressed energy gap due to magnetic vortices in the S leads at some distance from the junction.Item Magnetic-field-induced stabilization of nonequillibrium superconductivity in a normal-metal/insulator/superconductor junction(2011-12-14) Peltonen, J.T.; Muhonen, J.T.; Meschke, M.; Kopnin, N.B.; Pekola, J.P.; Department of Applied PhysicsA small magnetic field is found to enhance relaxation processes in a superconductor, thus stabilizing superconductivity in nonequilibrium conditions. In a normal-metal (N)/insulator/superconductor (S) tunnel junction, applying a field of the order of 100μT leads to significantly improved cooling of the N island by quasiparticle (QP) tunneling. These findings are attributed to faster QP relaxation within the S electrodes as a result of enhanced QP drain through regions with a locally suppressed energy gap due to magnetic vortices in the S leads at some distance from the junction.Item Metallic Coulomb blockade thermometry down to 10 mK and below(AIP Publishing, 2012) Casparis, L.; Meschke, M.; Maradan, D.; Clark, A. C.; Scheller, C. P.; Schwarzwälder, K. K.; Pekola, Jukka P.; Zumbühl, D. M.; Department of Applied Physics; Teknillisen fysiikan laitos; Perustieteiden korkeakoulu; School of ScienceWe present an improved nuclear refrigerator reaching 0.3 mK, aimed at microkelvin nanoelectronic experiments, and use it to investigate metallic Coulomb blockadethermometers (CBTs) with various resistances R. The high-R devices cool to slightly lower T, consistent with better isolation from the noise environment, and exhibit electron-phonon cooling ∝ T 5 and a residual heat-leak of 40 aW. In contrast, the low-R CBTs display cooling with a clearly weaker T-dependence, deviating from the electron-phonon mechanism. The CBTs agree excellently with the refrigerator temperature above 20 mK and reach a minimum-T of 7.5 ± 0.2 mK.Item Nanosecond Thermometry with Josephson Junctions(2018-10-29) Zgirski, M.; Foltyn, M.; Savin, A.; Norowski, K.; Meschke, M.; Pekola, J.; Institute of Physics of the Polish Academy of Sciences; Centre of Excellence in Quantum Technology, QTF; Department of Applied PhysicsWe demonstrate a new paradigm in nanoscale thermometry exploiting well-known switching measurements of a superconducting weak link. Such a weak link probed with nanosecond current pulses serves as a temperature-sensing element and, because of the fast inherent dynamics, is capable of delivering unprecedented temporal resolution. We use the thermometer to measure the dynamic temperature of electrons in a long superconducting wire relaxing to the bath temperature after application of a heating pulse, involving evaluation of the retrapping time. Our measurement delivers resolution better than 10 ns, with potential for further improvement. It extends the temporal resolution of existing experiments and introduces new possibilities for investigating thermodynamics at the nanoscale.Item Non-hysteretic superconducting quantum interference proximity transistor with enhanced responsivity(AIP Publishing, 2014) Jabdaraghi, R. N.; Meschke, M.; Pekola, Jukka P.; Department of Applied Physics; Teknillisen fysiikan laitos; Perustieteiden korkeakoulu; School of ScienceThis Letter presents fabrication and characterization of an optimized superconducting quantum interference proximity transistor. The present device, characterized by reduced tunnel junction area and shortened normal-metal section, demonstrates no hysteresis at low temperatures as we increased the Josephson inductance of the weak link by decreasing its cross section. It has consequently almost an order of magnitude improved magnetic field responsivity as compared to the earlier design. The modulation of both the current and the voltage across the junction have been measured as a function of magnetic flux piercing the superconducting loop.Item On-and-off chip cooling of a Coulomb blockade thermometer down to 2.8 mK(2017-12-18) Palma, M.; Scheller, C. P.; Maradan, D.; Feshchenko, A. V.; Meschke, M.; Zumbühl, D. M.; Department of Applied Physics; Quantum Phenomena and Devices; University of BaselCooling nanoelectronic devices below 10 mK is a great challenge since thermal conductivities become very small, thus creating a pronounced sensitivity to heat leaks. Here, we overcome these difficulties by using adiabatic demagnetization of both the electronic leads and the large metallic islands of a Coulomb blockade thermometer. This reduces the external heat leak through the leads and also provides on-chip refrigeration, together cooling the thermometer down to 2.8 ± 0.1 mK. We present a thermal model which gives a good qualitative account and suggests that the main limitation is heating due to pulse tube vibrations. With better decoupling, temperatures below 1 mK should be within reach, thus opening the door for μK nanoelectronics.Item Origin of Hysteresis in a Proximity Josephson Junction(American Physical Society (APS), 2008) Courtois, H.; Meschke, M.; Peltonen, J. T.; Pekola, Jukka P.; Department of Applied Physics; Teknillisen fysiikan laitos; Perustieteiden korkeakoulu; School of ScienceWe investigate hysteresis in the transport properties of superconductor–normal-metal–superconductor (S-N-S) junctions at low temperatures by measuring directly the electron temperature in the normal metal. Our results demonstrate unambiguously that the hysteresis results from an increase of the normal-metal electron temperature once the junction switches to the resistive state. In our geometry, the electron temperature increase is governed by the thermal resistance of the superconducting electrodes of the junction.Item Parity effect in Al and Nb single electron transistors in a tunable environment(AIP Publishing, 2007) Savin, A. M.; Meschke, M.; Pekola, Jukka P.; Pashkin, Yu. A.; Li, T. F.; Im, H.; Tsai, J. S.; Department of Applied Physics; Teknillisen fysiikan laitos; Perustieteiden korkeakoulu; School of ScienceTwo different types of Cooper pair transistors, with Al and Nb islands, have been investigated in a tunable electromagnetic environment. The device with an Al island demonstrates gate charge modulation with 2e periodicity in a wide range of environmental impedances at bath temperatures below 340mK. Contrary to the results of the Al sample, the authors were not able to detect 2e periodicity under any conditions on similar samples with Nb island. The authors attribute this to the material properties of Nb.Item A robust platform cooled by superconducting electronic refrigerators(AIP Publishing, 2015) Nguyen, H. Q.; Meschke, M.; Pekola, Jukka P.; Department of Applied Physics; Teknillisen fysiikan laitos; Perustieteiden korkeakoulu; School of ScienceA 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 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 discussed our results and possibilities to further improve the device.Item A robust platform cooled by superconducting electronic refrigerators(2015) Nguyen, H.Q.; Meschke, M.; Pekola, J.P.; Department of Applied PhysicsA 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 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 discussed our results and possibilities to further improve the device.Item Shot-Noise-Driven Escape in Hysteretic Josephson Junctions(2005-11-03) Pekola, J. P.; Nieminen, T. E.; Meschke, M.; Kivioja, J. M.; Niskanen, A. O.; Vartiainen, J. J.; Department of Applied PhysicsWe have measured the influence of shot noise on hysteretic Josephson junctions initially in the macroscopic quantum tunneling regime. The escape threshold current into the resistive state decreases monotonically with increasing average current through the scattering conductor, which is another tunnel junction. Escape is predominantly determined by excitation due to the wideband shot noise. This process is equivalent to thermal activation (TA) over the barrier at effective temperatures up to about 4 times the critical temperature of the superconductor. The presented TA model is in excellent agreement with the experimental results.Item Shot-Noise-Driven Escape in Hysteretic Josephson Junctions(American Physical Society (APS), 2005) Pekola, Jukka P.; Nieminen, T. E.; Meschke, M.; Kivioja, J. M.; Niskanen, A. O.; Vartiainen, J. J.; Department of Applied Physics; Teknillisen fysiikan laitos; Perustieteiden korkeakoulu; School of ScienceWe have measured the influence of shot noise on hysteretic Josephson junctions initially in the macroscopic quantum tunneling regime. The escape threshold current into the resistive state decreases monotonically with increasing average current through the scattering conductor, which is another tunnel junction. Escape is predominantly determined by excitation due to the wideband shot noise. This process is equivalent to thermal activation (TA) over the barrier at effective temperatures up to about 4 times the critical temperature of the superconductor. The presented TA model is in excellent agreement with the experimental results.
