Search results for "CONDUCTIVITY"

Coherence properties in superconducting flux qubits

The research work discussed in this thesis deals with the study of superconducting Josephson qubits. Superconducting qubits are solid-state artificial atoms which are based on lithographically defined Josephson tunnel junctions properties. When sufficiently cooled, these superconducting devices exhibit quantized states of charge, flux or junction phase depending on their design parameters. This allows to observe coherent evolutions of their states. The results presented can be divided into two parts. In a first part we investigate operations of superconducting qubits based on the quantum coherence in superconducting quantum interference devices (SQUID). We explain experimental data which ha…

Applications and non-idealities of submicron Al–AlOx–Nb tunnel junctions

2016

We have developed a technique to fabricate sub-micron, 0.6µm×0.6µm Al-AlOx-Nb tunnel junctions using a standard e-beam resist, angle evaporation and double oxidation of the tunneling barrier, resulting in high quality niobium, as determined by the the high measured values of the critical temperature TC ∼ 7.5 K and the gap ∆ ∼ 1.3 meV. The devices show great promise for local nanoscale thermometry in the temperature range 1 - 7.5 K. Electrical characterization of the junctions was performed at sub-Kelvin temperatures both with and without an external magnetic field, which was used to suppress superconductivity in Al and thus bring the junction into a normal-metal-insulator-superconductor (NI…

Vacuum-Deposited Cesium Tin Iodide Thin Films with Tunable Thermoelectric Properties

2022

Most current thermoelectric materials have important drawbacks, such as toxicity, scarceness, and peak operating temperatures above 300 °C. Herein, we report the thermoelectric properties of different crystalline phases of Sn-based perovskite thin films. The 2D phase, Cs2SnI4, is obtained through vacuum thermal deposition and easily converted into the black β phase of CsSnI3(B-β CsSnI3) by annealing at 150 °C. B-β CsSnI3is a p-type semiconductor with a figure of merit (ZT) ranging from 0.021 to 0.033 for temperatures below 100 °C, which makes it a promising candidate to power small electronic devices such as wearable sensors which may be interconnected in the so-called Internet of Things. T…

Implementing the 3-omega technique for thermal conductivity measurements

2013

Thermal conductivity of the constituent materials is one of the most important properties affecting the performance of micro- and nanofabricated devices. These devices often make use of thin films with thicknesses ranging from some nanometers to few micrometers. The thermal conductivity of thin films can be measured with the three-omega method. In three-omega technique a metal wire acting as a resistive heater is microfabricated on the sample. Alternating current passing through the metal heater at a frequency ω heats the sample periodically and generates oscillations in the resistance of the metal line at a frequency 2ω. The oscillating resistance component is coupled with the driving curr…

Thin film conductivity measurements of carbon nanotube hemicellulose complex

2014

Työssä mitattiin hiilinanoputkista ja hemiselluloosasta koostuvan läpinäkyvän ohutkalvon sähkönjohtavuutta. Materiaali on Nemcel Oy:n kehittämä. Valmistimme useita näytteitä erilaisia mittauksia varten ja testataksemme eri valmistusmenetelmiä. Valmistetun ohutkalvon merkittävimmät ominaisuudet ovat läpinäkyvyys ja hyvä sähkönjohtavuus. Valmistetut kalvot olivat pääasiassa läpinäkyviä, mikä edellytti kalvon ohuutta. Itse materiaali toimitettiin vesiliuoksena, jossa oli 1:1 hiilinanoputkia ja hemiselluloosaa. Kalvot valmistettiin joko spinnaamalla tai kuivattamalla yksittäisiä pisaroita pinnalle. Näytteet valmistettiin pintaoksidioidulle piille, johon oli tehty kultaelektrodit. Kalvoa kuvatti…

Electrical conductivity of glass fiber-reinforced plastic with nanomodified matrix for damage diagnostic

2021

The electrical conductivity of glass fiber-reinforced plastic (GFRP) with epoxy matrix modified by multiwall carbon nanotubes (MWCNT) was studied. The electrical conductivity of nanomodified lamina and multi-layered GFRP was investigated on several levels using a structural approach. Components of the electrical conductivity tensor for unidirectional-reinforced monolayer were calculated similarly as in micromechanics using the conductivity of the nanomodified matrix. The electrical conductivity of multilayer composite was calculated using laminate theory and compared with values measured experimentally for various fiber orientation angles. Calculated and experimental data were in good agree…

Electrochemical treatment of real wastewater with low or high conductivity

2018

In the last years, many efforts have been devoted to the development of electrochemical processes for the effective treatment of wastewater contaminated by organic pollutants resistant to conventional biological processes and/or toxic for microorganisms [1–5]. It was shown that some electrochemical approaches, including the direct anodic oxidation at suitable anodes such as boron-doped diamond (BDD) and/or electro-Fenton (EF) at suitable operating conditions and cells [1–6] can allow to treat effectively a very large number of organic pollutants. However, most of the investigations were performed using synthetic wastewater. Hence, it is now mandatory to study the problems connected to the p…

Alternative analysis of transient infiltration experiment to estimate soil water repellency

2019

The repellency index (RI) defined as the adjusted ratio between soil‐ethanol, Se, and soil‐water, Sw, sorptivities estimated from minidisk infiltrometer experiments has been used instead of the widely used water drop penetration time and molarity of ethanol drop tests to assess soil water repellency. However, sorptivity calculated by the usual early‐time infiltration equation may be overestimated as the effects of gravity and lateral capillary are neglected. With the aim to establish the best applicative procedure to assess RI, different approaches to estimate Se and Sw were compared that make use of both the early‐time infiltration equation (namely, the 1 min, S1, and the short‐time linear…