1,721,070 research outputs found
Superconducting and Dissipative Characteristics of Overdamped SNIS Josephson Junctions for Sensing Applications
Full text linkJosephson-junction devices such as suitably designed nanoSQUIDs can provide a sensing element for micro and nanoelectronics. In this paper, the properties of such device must be tailored in order to have an optimal response. In particular, it relates its temperature stability, and a comparatively weak dependence of the critical supercurrent Ic on temperature Tin the working range. To realize it, a concave upward Ic-versus-T curve is required. The aim of this paper was to study conditions when such temperature dependence can be realized in four-layered S/N-I-S Josephson junctions, mantaining the overdamped behavior. We show how the shape of the Ic-versus-T dependence can provide important information about the strength of the S/N proximity coupling
Cryogen-Free Operation of SNIS for AC Quantum Voltage Standards
Full text linkWe report on our recent and ongoing activities on helium-free operation with ac Josephson standards based on programmable superconductor-normal conductor-insulator-superconductor (SNIS) arrays. Liquid helium-free operation provides ease of use, which is a wider number of applications and users. Moreover, it allows to reduce cable loading, which is crucial to overcome frequency-related limitations to the accuracy. Thermalization problems not faced with helium cooling are still challenging, in particular with programmable standards. To identify the effect of He-free cooling on electrical behavior, we compared the array steps in cryocooler a liquid helium. Results show that SNIS arrays can be operated in cryocooler and are interesting for application to programmable voltage standard
Geometry Dependent Superconductive Transition of Nb Nanostructures
Full text linkRecently, superconducting nanostructures gained particular attention due to the visualisation of some intriguing phenomena, such as phase fluctuations, quantum phase slip, and shape resonance in critical temperature, allowing the definition of a tailored superconducting nanodevice with the desired superconducting features and quantum phenomena. A deep investigation into the relationship between superconductivity, low dimensionality, and quantum phenomena should be performed, in order to explain the emergence mechanism of these effects in nanostructures and how superconductivity is affected. In the following, we report on the investigation of the superconductive transition in triangular-shaped Nb pads connecting a Nb nanostripe. As revealed by R vs T curves, the superconductive transition is observed to be characterised by two regions: i) a first smooth and wide transition reflecting the continuous reduction in the width of the Nb triangular pads that progressively experience superconductive transition, and ii) a more abrupt transition reflecting the transition of the Nb nanostripe. This work could pave the way concerning the realisation of Nb nanostructures with tunable critical temperature, transition width, and slope
Superconductivity in primary voltage metrology at INRiM
No full textPrimary electrical Metrology is among the first and, to date, one of the most active and successful research field for superconducting devices. Voltage standards based on the Josephson effect are in use since few years after it discovery and have enormously reduced the uncertainty of DC voltage calibrations. INRIM the Italian National Metrology Institute has a long tradition in research on the application of superconductivity to electrical standards. This paper is an overview of main results and ongoing activities
On the synthesis of stepwise quantum waves using a SNIS programmable josephson array in a cryocooler
Full text linkThis paper presents recent advances in the application of binary-divided 1 V array, consisting of 8192 intrinsically shunted SNIS overdamped Josephson junctions (JJs), for the synthesis of stepwise waves with quantum accuracy. The maximum output voltage is ensured by opportunely driving the subsections of the SNIS array by means of three states bias-current setpoints to the Shapiro steps n = 0, +/- 1 or n = +/- 2, respectively. Reconfigurable digital modular electronics has been designed to bias individually each of the 13 subsections of the SNIS array. A two-stage closed cycle refrigerator equipped with LF and RF electrical lines is employed for cooling-down the SNIS array for temperatures ranging from 3.6 K to above 7 K. Stepwise sine waves with rms amplitude ranging from 1 to 2 V using the first (n = 1) and second (n= 2) Shapiro steps, different temperatures and bias-current setpoints have been synthesized up to the kHz range. The synthesized waves have been recorded and analyzed by a high-precision differential sampling system. We report the results of the first characterizations carried out with the new multibit current source and an improved version of the sample holder designed to optimize the heat dissipation of the SNIS array for operation in cryocooler setups
Experimental and Modeling Study of Metal–Insulator Interfaces to Control the Electronic Transport in Single Nanowire Memristive Devices
Full text linkMemristive devices relying on redox-based resistive switching mechanisms represent promising candidates for the development of novel computing paradigms beyond von Neumann architecture. Recent advancements in understanding physicochemical phenomena underlying resistive switching have shed new light on the importance of an appropriate selection of material properties required to optimize the performance of devices. However, despite great attention has been devoted to unveiling the role of doping concentration, impurity type, adsorbed moisture, and catalytic activity at the interfaces, specific studies concerning the effect of the counter electrode in regulating the electronic flow in memristive cells are scarce. In this work, the influence of the metal-insulator Schottky interfaces in electrochemical metallization memory (ECM) memristive cell model systems based on single-crystalline ZnO nanowires (NWs) is investigated following a combined experimental and modeling approach. By comparing and simulating the electrical characteristics of single NW devices with different contact configurations and by considering Ag and Pt electrodes as representative of electrochemically active and inert electrodes, respectively, we highlight the importance of an appropriate choice of electrode materials by taking into account the Schottky barrier height and interface chemistry at the metal-insulator interfaces. In particular, we show that a clever choice of metal-insulator interfaces allows to reshape the hysteretic conduction characteristics of the device and to increase the device performance by tuning its resistance window. These results obtained from single NW-based devices provide new insights into the selection criteria for materials and interfaces in connection with the design of advanced ECM cells
- …
