There has been a recent resurgence in interest in developing ohmic switches to complement transistors in order to address challenges associated with electrical current leakage. A critical limitation in ohmic switches remains the reliability of their electrical contacts. These contacts are prone to hydrocarbon induced contamination which progressively inhibits signal transmission, eventually leading to device failure. We report on progress made towards controlling the contamination phenomenon. We discuss how contact materials and operating environment affect device performance, showing that RuO2 coated microswitch contacts operating in the presence of O2 experience very limited contaminant accumulation even in hydrocarbon-rich environments. We then demonstrate that devices which have experienced contamination can recover their original performance by being operated in clean N2:O2 environment. Finally, we suggest that this resistance recovery is associated with the chemical transformation of the contaminant as opposed to its removal and that the transformed contaminant may shield the Pt coating from oxidation.

Silicon carbide (SiC) has long been known as a robust semiconductor with superior properties to silicon for electronic applications. Consequently a tremendous amount of international activity has been on-going for over four decades to develop high-power solid state SiC electronics. While this activity has focused on the hexagonal polytypes of SiC, the only form that can be grown directly on Si substrates, 3C-SiC (or cubic SiC), has been researched for non-electronic applications such as MEMS and biosensors. In particular in our group we have pioneered several biomedical devices using 3C-SiC grown on Si substrates, and recently have been investigating the use of this novel material for clean energy applications. This paper first reviews progress made in the area of 3C-SiC electronic devices. Next a review of nearly a decade of biomedical activity is presented, with particular emphasis on the most promising applications: in vivo glucose monitoring, biomedical implants for connecting the human nervous system to advanced prosthetics, and MEMS/NEMS research aimed at allowing for in vivo diagnostic and therapeutic systems for advanced biomedical applications. Recent published work in the area of hydrogen production via electrolysis using 3C-SiC closes the paper as this last application is extremely promising for the burgeoning hydrogen economy and demonstrates a third important application of 3C-SiC on Si – its potential use in clean energy systems.

Recently, major advances have been made in electrolytic and solid state DSSCs through the use of perovskite nanocrystals as a sensitizing agent where power conversion efficiencies of over 12% have been realized [1–3]. Moreover the planar DSSC/PV devices with perovskites used as photoactive absorbers sandwiched between selective electron and hole transport layers have demonstrated record performances. Additionally, the uses of carbon nanotubes (CNTs) as a flexible, transparent, lightweight and robust electrode material have been demonstrated in both DSSC as well as OPV devices. The application of CNTs as a charge collector with perovskite sensitized solid state planar PV and DSSCs is discussed. Performance characteristics of CNTs within perovskite based hybrid OPVs are investigated and the role of CNTs as an efficient charge collector is extended to the inverted geometry.

Assembly of nanowires into ordered macroscopic structures has attracted great scientific interests in the past decade. In this work, we report a rapid low-cost scalable oil-water interfacial self assembly process for fabricating aligned Ag nanowires (AgNWs) films on solid substrates. This process is much simpler than the traditional Langmuir-Blodgett (LB) techniques and allows the assembly of one–dimensional Ag nanowires onto any solid substrates without extra pretreatment of the surface of silver nanowires or the solid substrate. The present aligned AgNW films can serve as robust surface-enhanced Raman scattering (SERS) sensors for chemical and bimolecular detection with improved spectra quality and demonstrated uniformity of SERS signal using R6G dye as probe.

We have been developing a collection of low-cost experiments for exploring the science of glassy materials through hands-on activities with sucrose based glass (a.k.a. hard candy). These form a mini-curriculum of glass science, consisting of inter-related experiments and home built apparatuses. It provides an environment to develop an understanding of glassy materials through active, prolonged engagement. Some of our earlier experiments were reported four years ago[1]. Since that report we have made substantial improvements and added new topics, including electrical and thermal conductivity, an improved DTA apparatus, and improved methodology for crystallization kinetics. All of our experiments are designed to be low-cost (typically <$100) and the apparatuses are designed for construction by students or teachers.

Several strategies have been explored from viewpoint of biomimetics to accomplish artificial photosynthesis by using macromolecules as a medium such as liposomes, supramolecules, and hydrogels.1 Differing from disordered solution systems in which multiple components such as photosensitizer and catalytic nanoparticle are diffusively mixed, the photochemical reactions occur efficiently in medium due to maintenance of the dipersibility of the components and specific molecular arrangement. Here we attempt to clarify the effect of medium hierarchy for photoinduced electronic transmission among multiple components. By conjugating each component on tubulin and integrating them via self-assembly to microtubules, ideal component arrangements with optimum distance for the electronic transmission will be possible.

A new approach for functionalising oxidised MWCNTs using hydroxylated imidazolium bromide via esterification reaction is reported. The bromide anion of a functionalised MWCNTs was exchanged with bis(trifluoromethanesulfonyl) imide (TFSI) through a metathesis reaction to improve its solubility in the IL medium. Composite was characterized with IR, XPS, EDX and TGA analysis, which clearly confirmed that the MWCNTs were functionalized with IL. For potential application as lubricant, the tribological properties of the IL-functionalised MWCNTs (MWCNT-IL) were also evaluated. It was confirmed that even low concentrations of MWCNT-IL composite in ILs causes a significant improvement in the anti-wear and friction properties.

Here we investigate how charge transport properties scale down to the nanoscale regime, comparing the properties to standard semiconductor materials and providing a perspective on what it means to device manufacturing. Strontium titanate - the prototypical oxide material - has been widely studied for applications in thermoelectrics, nanoelectronics, catalysis, and other uses. We investigated how charge transport is effected at interfaces to strontium titanate under a wide range of conditions - by varying contact size, interface shape, dopant concentration, surface structures and in various combinations and relate the results to experiments utilizing standard semiconducting materials such as silicon and gallium arsenide. Also, the results of the analysis has wide ranging implications, especially for ferroelectric perovskite materials and serves as the basis for understanding and controlling switching effects - both polarization and oxygen migration based switching.

Ce3+ is known to show broad optical emission peaking in the green spectral range. For the stabilization of 3-valent cerium in ceramic phosphors such as calcium scandate CaSc2O4, often co-doping with sodium for charge compensation is performed (Na+, Ce3+ ↔ 2 Ca2+). At the melting point of CaSc2O4 (≈2110°C), however, alkaline oxides evaporate completely and co-doping is thus no option for crystal growth from the melt. It is shown that even without co-doping Ce3+:CaSc2O4 crystal fibers can be grown from the melt by laser-heated pedestal growth (LHPG) in a suitable reactive atmosphere. Reactive means here that the oxygen partial pressure is a function of temperature and p O2(T) rises for this atmosphere in such a way that Ce3+ is kept stable for all T. Crystal fibers with ≈1 mm diameter and ≤50 mm length were grown and characterized. Differential thermal analysis (DTA) was performed in the pseudo-binary system CaO–Sc2O3, and the specific heat capacity c p (T) of CaSc2O4 was measured up to 1240 K by differential scanning calorimetry (DSC). Near and beyond the melting point of calcium scandate significant evaporation of calcium tends to shift the melt composition towards the Sc2O3 side. Measurements and thermodynamic calculations reveal quantitative data on the fugacities of evaporating species.

Water-soluble associative polyelectrolytes of methacrylic acid [MAA] and ethyl acrylate [EA] (1:1 molar ratio), hydrophobically modified with small amounts of stearyl metacrylate [MM18], were synthesized by means of solution polymerization. Polyelectrolytes with two different molecular structures: multisticker, with hydrophobic groups randomly distributed along the hydrophilic chain and combined, with the hydrophobic groups along the chain and as terminal groups of the backbone, were obtained. Steady shear behavior and linear viscoelastic properties were studied as a function of polymer microstructure and hydrophobic group concentrations on salt-free aqueous solution using a cone-and-plate rheometer. Concentration regimes were obtained for each synthetized polymer. Viscoelastic study shows that the maximum thickening effect corresponds to the combined structure followed by multisticker structure. These polyelectrolytes exhibit high thickening power on aqueous solutions due to the synergy between the hydrophobic attractive interactions and coil expansion phenomena.

The BiFeO3 (BFO) / PbTiO3 (PT) multiferroic ceramic composites with multilayered structure were prepared from orderly laminated BFO and PT tapes by tape casting method. The dielectric constant ε r , loss tanδ, remnant polarization P r and field-induced strain of BFO/PT ceramic composites were 140 (1 kHz), 5% (1 kHz), 12 µC/cm2 (at 80 kV/cm) and 0.06% (at 80 kV/cm) respectively, which were comparable to those pure BFO ceramics and BFO-based solid solutions

Effect of residual stresses of multiple welding repairs on API 5L X52 pipeline steel on stress corrosion cracking (SCC) in a simulated acidic soil solution was studied. Four conditions of repairs of the girth weld were evaluated. The residual stresses were measured through X-ray diffraction (XRD) on the internal side of the pipe in longitudinal and circumferential direction. The circumferential and longitudinal residual stresses values are compressive on the inner surface of the welding joints. The highest residual stresses were measured in the hoop direction reaching values of about 98% of the yielding strength (360 MPa). It was observed that its magnitude increases as move away from weld center line. The effect of residuals stresses in the SCC susceptibility of X52 pipeline steel was evaluated through slow strain rate tests (SSRT) in a simulated acidic soil solution. Relation between mechanical properties obtained from SSRT and residual stresses on the SCC susceptibility was analyzed. Results of SCC index taking account the ratios obtained from the mechanical properties of the welding joints evaluate, showed good SCC resistance in acidic soil solution at low pH. Scanning electron microscopy (SEM) observations showed that the region with high residual stresses prior to generate cracks in the steel due to the combination of soil solution and the strain exerted, should favor pitting formation and not cracking.

The massive crystal growth of single crystal semiconductors materials has been of fundamental importance for the actual electronic devices industry. As a consequence of this one, we can obtain easily a large variety of low cost devices almost as made ones of silicon. Nowadays, the III-V semiconductors compounds and their alloys have been proved to be very important because of their optical properties and applications. It is the case of the elements In, Ga, As, Sb, which can be utilized for the fabrication of radiation sensors. In this work we present the results obtained from the ingots grown by the Czochralski method, using a growth system made in home. These results include anisotropic chemical attacks in order to reveal the crystallographic orientation and the possible polycrystallinity. Isotropic chemical attacks were made to evaluate the etch pit density. Metallographic pictures of the chemical attacks are presented in this work. Among the results of these measurements, the best samples presented in this work showed mobilities of 62.000 cm2/V*s at room temperature and 99.000 cm2/V*s at liquid nitrogen temperature. Typical pit density was 10,000/cm2. The Raman spectra present two dominant peaks associated at Transversal Optical (TO)- and Longitudinal Optical (LO)-InSb, the first vibrational mode is dominant due to the crystalline direction of the ingots and second one is associated to high defects density.

Light-emitting diodes (LEDs) made from wide band gap semiconductors, such as gallium nitride, are undergoing rapid development. Solid-state lighting with these LEDs is transforming patterns of energy usage and lifestyle throughout the world.

With solid-state lighting gradually taking over from incandescent and fluorescent lighting, light-emitting diodes (LEDs) are very much the focus of research nowadays. This compact review takes a look at LEDs for lighting applications made from wide band gap semiconductors. A very brief history of electric lighting is included for completeness, followed by a description of blue-emitting LEDs that serve as pump sources for all ‘white’ LEDs. This is followed by a discussion on techniques to extract more light from the confines of LED chips through surface patterning. The thermal management of LEDs is perhaps the most important consideration in designing and using LED-based luminaires. This topic is discussed with regard to recent studies on LED reliability. The very promising development of gallium nitride-on-silicon LEDs is examined next followed by a discussion on phosphors for color conversion in LEDs. LED lighting has positively influenced both upscale and downscale illumination markets worldwide. Its societal impact is examined, with the review concluding with a look at efforts to produce LEDs from zinc oxide – a material that holds much promise for the future of solid-state lighting.

Electrophoretic deposition enables the rapid deposition of single wall carbon nanotube films at room temperature. An accurate, reproducible film thickness can be obtained by controlling electric field strength, suspension concentration, and time. To investigate the electrical and mechanical properties of such films, we recorded electric resistance and Young’s modulus using I-V characterization and a nanoindenter, respectively. The measured resistivity of the films varied from 2.14 × 10-3 to 7.66 × 10-3 Ω·cm, and the Young’s modulus was 4.72 to 5.67 GPa, independent of film thickness from 77 to 134 nm. These results indicated that the mechanical and electrical properties of film are comparable with previously reported methods such as layer by layer deposition even though we achieved much higher deposition rates. We also measured the film mass density which is usually unrecorded even though it is an important parameter for MEMS/NEMS device actuation. The film density was found with conventional thickness measurement and Rutherford backscattering spectrometry. It varied from 0.12 to 0.54 g/cm3 as the film thickness increased. This method could be extended to applications of CNT films for flexible electronics or high frequency RF MEMS devices.

At the Great Temple of Tenochtitlan, the archaeologists found hundreds of stone masks considered foreign pieces obtained by commerce, tribute, and pillage. Because of that, they were classified in the main Mesoamerican styles, like the Olmec, Mezcala, Teotihuacan, Mayan, Mixtec and Aztec art. Among them are seven Teotihuacan Style masks found in five offerings. Its presence was explained by other researchers as relics looted by Aztec people from the Teotihuacan site, because the Aztec priests and rulers employed them as sources of power, prestige and mythical links between the City of the Gods and Tenochtitlan. But, are these stone masks from Tenochtitlan really Teotihuacan items? How can we identify which of them came from Teotihuacan and could be relics and which of them not? To solve this problem, we analyze its manufacturing techniques and compare them with lapidary objects from different areas of Teotihuacan, employing experimental archaeology, Optic Microscopy and Scanning Electron Microscopy. As results, we identify two technological patterns: five masks share the tools and techniques of Teotihuacan manufactures but two other masks contrast with them. Interestingly, its technology match with the Tenochcan productions, so, both pieces could be recreations crafted by Aztec artisans during the Postclassic times.

We improve the efficiency of a bottom-emitting red phosphorescent organic light emitting diode (OLED) by the suppression of wave-guided modes in the bottom contact. ITO as bottom contact layer has been substituted by a thin Ti/Au layer. Electromagnetic simulation results of both devices predict the absence of TE polarized guided contact modes by the use of 10 nm Au as bottom electrode. We measured an improved outcoupling of light which overcompensates absorption losses of the Ti/Au layer in the measured emission cone. By the use of 1 nm Ti as undercoat, a continuous Au film of 8 nm thickness could be realized with an improved transmittance for long wavelengths (λ > 550 nm). As a consequence of fewer lateral guided modes, the external quantum efficiency (EQE) has been enhanced from 11.5 % of the standard device to 14 % of the device with the Ti/Au electrode.

Cellulose nanofibers (Cel-F) were extracted by a simple and harmless Star Burst (SB) method, which produced aqueous cellulose-nanofiber solution just by running original cellulose beads under a high pressure of water in the synthetic SB chamber. By optimizing the SB process conditions, the cellulose nanofibers with high aspect ratios and the small diameter of ∼23 nm were obtained, which was confirmed by transmission electron microscopy (TEM). From the structural analysis of the Cel-F/PVA composite by the scanning electron microscopy (SEM), it was found that the Cel-F were homogeneously dispersed in the PVA matrix. Considering the high molecular compatibility of the cellulose and PVA due to the hydrogen bonding, a good adhesive interface could be expected for the Cel-F and the PVA matrix. The influences of the morphological change in Cel-F on the mechanical properties of the composites were analysed. The Young’s modulus rapidly increased from 2.2 GPa to 2.9 GPa up to 40 SB treatments (represented by the unit Pass), whereas the Young’s modulus remained virtually constant above 40 Pass. Due to the uniform dispersibility of the Cel-F, the Young’s modulus of the 100 Pass composite at the concentration of 5 wt% increased up to 3.2 GPa. The experimental results corresponded well with the general theory of the composites with dispersed short-fiber fillers, which clearly indicated that the potential of the cellulose nanofibers as reinforcement materials for hydrophilic polymers was sufficiently confirmed.

Inkjet printing is a well-accepted deposition technology for functional materials in the area of printed electronics. It allows the precise deposition of patterned functional layers on both, rigid and flexible substrates. Furthermore, inkjet printing is considered as up-scalable technology towards industrial applications. Many electronic devices manufactured with inkjet printing have been reported in the recent years. Some of the evident examples are capacitors, resistors, organic thin film transistors and rectifying Schottky diodes. [1, 2, 3] In this paper we report on the manufacturing of an inkjet-printed metal-insulator-semiconductor (MIS) diode on flexible plastic substrate. The structure is comprised of an insulating and a polymeric semiconducting layer sandwiched between two silver electrodes. The current vs. voltage characteristics are rectifying with rectification ratio up to 100 at |4 V|. Furthermore, they can carry high current densities (up to mA/cm2) and have a low capacitance which makes them attractive for high frequency rectifying circuits. They are also an ideal candidate to replace conventional Schottky diodes for which the fabrication remains a challenge. This is because inkjet printing of Schottky diodes require additional processing steps such as intense pulsed light sintering (IPL sintering) [4] or post-treatments at high temperatures. The deposition of two different metal layers using inkjet printing e.g. Cu or Al with Ag is possible. However, the mentioned post treatment technologies might be incompatible with the already existing layer stack– e.g. it could degrade the organic semiconductor or can damage insulator which in this case is present in the MIS diode architecture.