In this work, we present an approach towards achieving a detailed knowledge on the effects of irradiation in iron-based superconductors with high-energy heavy ions. Ba1−xKxFe2As2 single crystals (x = 0.42) were irradiated with 250 MeV Au-ions. The crystals were shaped to be thin plates with thickness lower than the ion implantation depth and bases perpendicular to the c-axis. By means of the quantitative magneto-optical imaging technique we attained the local current density in pristine and irradiated sample regions without any model assumption. After irradiation a strong critical current density (Jc) enhancement was measured, overcoming a factor 3 at T = 4 K with an irradiation fluence φ = 9.7 × 109 cm-2. Moreover, correlating point by point Jc and induction magnetic field maps, a contribution of the Au-ion induced defects to the anisotropic out of plane pinning (i.e. pinning in the direction parallel to the ion path) turned up. This contribution shows a maximum at applied fields quite lower than the nominal dose equivalent field. Furthermore, the temperature dependence of the penetration depth was evaluated before and after high-fluence irradiations by investigating the high-frequency behavior of these crystals using a microwave coplanar resonator technique. Fitting the experimental curves with a power law, we found a decrease of the power exponent, more pronounced at the higher fluences, that can supports the s± wave model.

The high-temperature performance of electronics packages was studied at 180°C, 200°C and 240°C for 3,000h. The structure tested consisted of a fairly large silicon chip attached with anisotropic conductive adhesive (ACA) onto an adhesiveless PI substrate. These structures showed good electrical reliability at 180°C. Several early failures were seen at the other temperatures. However, only 23% of the test samples failed at 200°C, while considerably more failures were seen at 240°C. The results showed that good high-temperature reliability can be achieved with polymer interconnections. However, the exposure time should be limited, especially at very high temperatures, to avoid failures caused by the materials becoming brittle.

Fabrication methods and performance characteristics of spiral stretchable interconnects fabricated using drop-on-demand printing of silver reactive inks are discussed. This work details ink optimization, device fabrication, and device characterization while demonstrating the potential applications for reactive inks and new design strategies in stretchable electronics. Devices were printed with an ethanol stabilized silver diamine reactive ink and cycled to 160 % over 100 cycles with less than 10% increase in electrical resistance. Maximum deformation before failure was measured at 180% elongation. A novel method for fabrication of a stretchable electronics device has been studied and verified.

Stretchable and flexible electronic devices have gained significant attention in recent years, as they can be integrated into many systems such as medical sensors, displays, and robots. One of the primary areas of research is designing stretchable interconnects which provide adequate conductivity and mechanical robustness. Metal-based interconnects have been reported to have the highest conductivity, but are not stretchable enough, while elastomer interconnects are not conductive enough. In this paper we report on a silver polymer blend composite that provides excellent conductivity, stretchability and flexibility for use as a stretchable interconnect. The composite was prepared by dispersing silver flakes in a Polyvinyl alcohol (PVA), Phosphoric acid (H3PO4) and poly(3,4-ethyl-ene-dioxythiophene) (PEDOT):Poly(styrene sulfonic acid) (PSS) polymer mixture. Silver was chosen as it has the highest conductivity of all metals, while the PEDOT:PSS/PVA- H3PO4 blend was chosen as the blend offers a practical trade-off between conductivity and stretchability for the composite matrix. The polymer blend provides conductive pathways between the silver flakes, leading to the blend’s superior electrical properties, even at large deformations. The synthesis process of the composite material, along with the observed electrical and mechanical properties under various straining conditions of the composite will be presented in detail.

Polyethylene terephthalate (PET) is an interesting flexible substrate material for many applications in electronics since it is inexpensive and has good mechanical and electrical properties. Due to these good properties there is increasing interest in using PET in applications involving harsh environments. However, PET has relatively poor thermal properties, which may cause reliability concerns in demanding conditions. Above its glass transition temperature, Tg, PET is susceptible to hydrolysis, which may considerably restrict its use. Hydrolysis breaks the molecular structure of PET and makes the material mechanically unreliable. This paper reports the reliability of PET films in an LCD display application and in RFID tags in thermal and humid conditions. Additionally, neat PET films were studied. Several thermal cycling and humidity tests were used. The results clearly showed that above the Tg of PET the combined effect of humidity and high temperature caused PET to become brittle leading to considerable reliability problems. However, in dry thermal cycling conditions and in humid conditions below the Tg of PET, the reliability of PET was found to be excellent even under prolonged exposure.

Persistent current joints are a critical component of commercial superconducting magnets.The standard jointing method widely used in the magnet industry for technological low temperature superconducting wires such as NbTi and Nb3Sn wires uses a superconducting solder (e.g. PbBi). In these joints the physical and superconducting properties of the solder materials inevitably play an important role in the overall performance of the joint. Key requirements for superconducting solders include low melting point to prevent degradation of the superconducting filaments during joining, good wettability of the superconducting filaments, suitable liquid phase viscosity, and finally adequate superconducting properties to enable sufficient supercurrent to pass through the joint under typical operating conditions (typically at 4.2K in a field of 1 T for an MRI magnet). PbBi solder satisfies all these criteria, but restrictions on the use of lead in the magnet industry are expected in the relatively near future, so new lead-free jointing techniques need to be developed.

One approach is the development of superconducting lead-free solder materials. In our work, we have focussed on the In-Sn system and ternary systems involving In and Sn as two of the elements. Thermodynamic modelling has been used to produce ternary phase diagrams of potential alloy systems, and various formulations have been fabricated in order to explore how microstructure and phase chemistry influence the superconducting properties of the solders. Alternative approaches to fabricating lead-free joints, including spot welding and cold-pressing, have also been investigated. These methods have the potential advantage of achieving direct NbTi-NbTi joints with no intermediate, lower performance superconducting material. The spot welding method produced joints with the best superconducting performance, signifiantly better than the currently used PbBi solder, but the lack of reproducibility in this technique may be a problem from an industrial point of view.

Diamond-based rectifiers are promising devices for the development of next-generation power electronics. However, presented device structures limit current operation as low as tens A, which hampers diamond from real industrial applications. One of the critical issues is poor availability of conductive (low-resistivity) substrates which can be used for vertical-type devices for high-output operations. Recently, we have successfully fabricated heavily boron-doped (p+) low-resistivity diamond by hot-filament chemical vapor deposition (HFCVD). Resistivity was monotonically decreased to 1.2 mΩcm with amount of doped boron. In this study, to further investigate potentials for electric applications, contact resistance between metal/p+ diamond was evaluated by transmission line model (TLM). From the current-voltage characteristics, low specific contact resistance of ∼10−7 Ωcm2 was demonstrated.