Search results for "Tunnel junction"
showing 10 items of 75 documents
Influence of Phonon dimensionality on Electron Energy Relaxation
2007
We studied experimentally the role of phonon dimensionality on electron-phonon (e-p) interaction in thin copper wires evaporated either on suspended silicon nitride membranes or on bulk substrates, at sub-Kelvin temperatures. The power emitted from electrons to phonons was measured using sensitive normal metal-insulator-superconductor (NIS) tunnel junction thermometers. Membrane thicknesses ranging from 30 nm to 750 nm were used to clearly see the onset of the effects of two-dimensional (2D) phonon system. We observed for the first time that a 2D phonon spectrum clearly changes the temperature dependence and strength of the e-p scattering rate, with the interaction becoming stronger at the …
Superconductor-ferromagnet tunnel junction thermoelectric bolometer and calorimeter with a SQUID readout
2020
Superconductor-ferromagnet thermoelectric detector (SFTED) is a novel ultrasensitive radiation detector based on the giant thermoelectric effect in superconductor-ferromagnet tunnel junctions. This type of detector can be operated without the need of additional bias lines, and is predicted to provide a performance rivaling transition-edge sensors and kinetic inductance detectors. Here we report our numerical studies on the SFTED noise equivalent power, energy resolution and time constant, and the feasibility of a SQUID readout in both bolometric and calorimetric regimes, with the goal to provide practical design parameters for the detector fabrication and the readout circuitry implementatio…
Preparation of Heusler thin films: The quaternary alloy CO2Fe0.5Mn0.5Si
2008
In this work the basic strategies for the preparation of CO2Mn0.5Fe0.5Si as an example for Heusler alloy thin films will be described. Texture and magnetic properties of these films will be discussed, especially with regard to different buffer layers and annealing temperatures. Finally, we will show the integration of Heusler thin films into magnetic tunnel junctions (MTJs) and calculate the effective spin polarization. (c) 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Exploring room-temperature transport of single-molecule magnet-based molecular spintronics devices using the magnetic tunnel junction as a device pla…
2019
A device architecture utilizing a single-molecule magnet (SMM) as a device element between two ferromagnetic electrodes may open vast opportunities to create novel molecular spintronics devices. Here, we report a method of connecting an SMM to the ferromagnetic electrodes. We utilized a nickel (Ni)–AlOx–Ni magnetic tunnel junction (MTJ) with the exposed side edges as a test bed. In the present work, we utilized an SMM with a hexanuclear [Mn6(μ3-O)2(H2N-sao)6(6-atha)2(EtOH)6] [H2N-saoH = salicylamidoxime, 6-atha = 6-acetylthiohexanoate] complex that is attached to alkane tethers terminated with thiols. These Mn-based molecules were electrochemically bonded between the two Ni electrodes of an…
Carrier transport mechanism in the SnO(2):F/p-type a-Si:H heterojunction
2011
We characterize SnO(2):F/p-type a-Si:H/Mo structures by current-voltage (I-V) and capacitance-voltage (C-V) measurements at different temperatures to determine the transport mechanism in the SnO2:F/p-type a-Si:H heterojunction. The experimental I-V curves of these structures, almost symmetric around the origin, are ohmic for vertical bar V vertical bar< 0:1 V and have a super-linear behavior (power law) for vertical bar V vertical bar < 0:1 V. The structure can be modeled as two diodes back to back connected so that the main current transport mechanisms are due to the reverse current of the diodes. To explain the measured C-V curves, the capacitance of the heterostructure is modeled as the …
Integrated SINIS refrigerators for efficient cooling of cryogenic detectors
2002
In this paper we report recent results obtained with large area superconductor-insulator-normal metal-insulator-superconductor tunnel junction coolers. With the devices we have successfully demonstrated electronic cooling from 260 mK to 80 mK with a cooling power of 20 pW at 80 mK. At present, we are focusing on obtaining similar performance in cooling cryogenic detectors. Additionally, we present recent results of successful operation of a metalsemiconductor structure with a Schottky barrier acting as the tunnel barrier and the possibility to use this kind of structures for on-chip cooling.
Noise and Microwave Properties of Set-Transistors
2002
Electron tunneling through a small tunnel junction with capacitance C 0 is suppressed by the so-called Coulomb blockade if the charging energy E c = e 2/2C∑ is larger than the thermal energy k B T 1. This effect is observed in a single electron tunneling transistor (SETT), which is a nano-meter size three-terminal device in which two leads connect to a small metallic island through two tunnel junctions. The excess charge on the island is regulated by the potential of the capacitively coupled gate electrode. The SETT is a very sensitive electrometer, noise levels of 10−5e/√Hz have been reached.2,3 A similar device, the electron pump, is made by connecting two or more islands in series throug…
Preparation of Ta-O-Based Tunnel Junctions to Obtain Artificial Synapses Based on Memristive Switching
2014
Magnetron sputtering and optical lithography are standard techniques to prepare magnetic tunnel junctions with lateral dimensions in the micrometer range. Here we present the materials and techniques to deposit the layer stacks, define the structures, and etch the devices. In the end, we obtain tunnel junction devices exhibiting memristive switching for potential use as artificial synapses.
Contrôle de nano-antennes optiques par une commande électrique : tuner plasmonique et transduction
2011
Optical nano-antennae are the new class of components to control light/matterinteraction at the nanoscale. These devices are operating in the visible to near infraredpart of the spectrum. The properties of these nano objects are controlled by theform, the size and the material.In the radio frequency domain, the tuner changes dynamically the operatingwavelength of the antenna. In this thesis work, we search to transfer this conceptto the nanoscale. The principle is to change the load impedance of the antenna, i.e.changing the optical index of the dielectric medium around the nano-object. Forthat we used anisotropic liquid cristal molecules. The value of the optical index iscontrolled by appl…
Observation of disorder-induced weakening of electron-phonon interaction in thin noble-metal films
2003
We have used symmetric normal metal-insulator-superconductor (NIS) tunnel junction pairs, known as SINIS structures, for ultrasensitive thermometry in the temperature range 50 - 700 mK. By Joule heating the electron gas and measuring the electron temperature, we show that the electron-phonon (e-p) scattering rate in the simplest noble metal disordered thin films (Cu,Au) follows a $T^4$ temperature dependence, leading to a stronger decoupling of the electron gas from the lattice at the lowest temperatures. This power law is indicative e-p coupling mediated by vibrating disorder, in contrast to the previously observed $T^3$ and $T^2$ laws.