Non-linear conductance at the superconductor-insulator transition in titanium nitride

The mechanism for the superconductor-insulator transition in disordered films, the transition from a weak superconductor into a strong insulator at low temperature, is still an open question. One key issue is whether superconductivity is the driving force of this insulating behavior and to which extent charging effects play a role. In this work high resolution dc current-voltage characteristics are presented. Non-linear behavior is found at high and low bias. The high bias non-linearity can be mainly attributed to electron overheating. The insulating state is analyzed in the framework of charge dominated Josephson junction arrays. The low-bias non-linearity can be attributed to a charge Berezinskii-Kosterlitz-Thouless transition displaying the duality of the superconducting and the insulating state

Dual threshold diode based on the superconductor-to-insulator transition in ultrathin TiN filmss

We investigate transport properties of superconducting TiN films in the vicinity of the superconductor-insulator transition (SIT). We show that the current-voltage (I-V) characteristics are mirror-symmetric with respect to the SIT and can be switched to each other by the applied magnetic field. In both superconducting and insulating states, the low-temperature I-V characteristics have pronounced diode-like threshold character, demonstrating voltage/current jumps over several orders of magnitude at the corresponding critical current or threshold voltage. We have found that for both states, the theory developed for Josephson junction arrays offers a quantitative description of the experimental results

Direct observation of the superconducting gap in thin film of titanium nitride using terahertz spectroscopy

We report on the charge carrier dynamics of superconducting titanium nitride (TiN) in the frequency range 90–510 GHz (3–17 cm−1). The experiments were performed on an 18-nm thick TiN film with a critical temperature of Tc=3.4 K. Measurements were carried out from room temperature down to 2 K, and in magnetic fields up to B=7 T. We extract the real and imaginary parts of the complex conductivity σ̂ as a function of frequency and temperature, directly providing the superconducting energy gap 2Δ. Further analysis yields the superconducting London penetration depth λL. The findings as well as the normal-state properties strongly suggest conventional BCS superconductivity, underlined by the ratio 2Δ(0)/kBTc=3.44. Detailed analysis of the charge carrier dynamics of the silicon substrate is also discussed

Re-reuse of regenerated brownfields: Lessons from an Eastern European post-industrial city

Brownfields constitute a substantial portion of the land area in post-industrial cities. Many brownfields have been regenerated for various uses, addressing a range of extant problems in urban areas. However, re-use plans for current brownfields are driven by market demand and public sector prioritization and do not always meet the requirements of local residents and visitors. In this paper, we investigate how a range of brownfields re-use options are perceived by residents and visitors to the Landek area in the city of Ostrava (Czech Republic). By analysing the results of the questionnaire survey (n = 180) we found that future brownfields uses such as culture/sport and children's park are the most popular options. We found that gender was a statistically significant predictor of preferred reuse options. Women are strong supporters of the above-mentioned re-use options, while men tend to favour re-use options which promote industry. Remarkably, respondents, in general, lacked concrete ideas concerning alternative re-use options of brownfields, suggesting that professional urban planners can be of assistance in the planning of the future use of brownfield sites. © 2018 Elsevier Ltd663830 CU126, EC, European Commission; Cardiff Universityproject Brownfields in urban and rural space: geographic, economic, historical, legal contexts and their importance for regional development (BURAN) [SGS/21/2016]; project Local development through local action groups: agriculture, local production, tourism and community management (FRRMS IGA) [2017/020]; University of the South Bohemia; Palacky University Olomouc; Tomas Bata University; COFUND Fellowship; Cardiff University, Welsh Government; European Commission [663830 CU126

Resonant-cavity LED transceiver arrays for optical wireless communication

155Mb/s operation of an optical wireless link is achieved by using the spectral characteristics and angular emission spectra of a 7-element tracking array of 980nm RC-LEDs. Preliminary results show extension to 200 Mb/s/channe