A change of solvent provides a means to modulate the intermetallic distance of the Ag ion chains in solvated structures of [AgI(cytidine-5'-monophosphate)], a 3D coordination polymer which features the less common O-2,N-3-binding mode for the nucleobase. Though the shortest Ag center dot center dot center dot Ag separation is within 5% of that in the metallic element, the coordination polymer is not electrically conducting, as shown by oriented singlecrystal I/V measurements. Band structure calculations for the isolated coordination chain ([Ag-(O-2,N-3-Cyt)](+))(n) also support this. Additionally, we demonstrate that these AgI ion chains are retained when crystalline MOF samples are processed as dispersions in the liquid phase by ultrasonication, yielding well-defined bilayer nanosheets through cleavage of phosphoester O-Ag bonds.

Health care quality measures are impacted by resources invested into outcomes. COVID-19 has had a direct impact upon quality outcomes, the same illuminating just some of the problems with the concept of a single-payer health care system. The US government's inefficiencies in attempting to run the single-payer system known as IHS in context with its repeated failures in managing the COVID-19 crises along with the economic impact of the same, is but one call for strong leadership to dispel the myth that a single-payer system is a panacea for America.

A simple, convenient method for the formation of hybrid metal/conductive polymer nanostructures is described. Polyimidazole (PIm) has been templated on λ-DNA via oxidative polymerisation of imidazole using FeCl3 to produce conductive PIm/DNA nanowires. The PIm/DNA nanowires were decorated with Pd (Pd/PIm/DNA) by electroless reduction of PdCl 4 2 − ?> with NaBH4 in the presence of PIm/DNA; the choice of imidazole was motivated by the potential Pd(II) binding site at the pyridinic N atom. The formation of PIm/DNA and the presence of metallic Pd on Pd/PIm/DNA nanowires were verified by FTIR, UV–vis and XPS spectroscopy techniques. AFM studies show that the nanowires have diameters in the range 5–45 nm with a slightly greater mean diameter (17.1 ± 0.75 nm) for the Pd-decorated nanowires than the PIm/DNA nanowires (14.5 ± 0.89 nm). After incubation for 24 h in the polymerisation solution, the PIm/DNA nanowires show a smooth, uniform morphology, which is retained after decoration with Pd. Using a combination of scanned conductance microscopy, conductive AFM and two-terminal measurements we show that both types of nanowire are conductive and that it is possible to discriminate different possible mechanisms of transport. The conductivity of the Pd/PIm/DNA nanowires, (0.1–1.4 S cm−1), is comparable to the PIm/DNA nanowires (0.37 ± 0.029 S cm−1). In addition, the conductance of Pd/PIm/DNA nanowires exhibits Arrhenius behaviour (Ea = 0.43 ± 0.02 eV) as a function of temperature in contrast to simple Pd/DNA nanowires. These results indicate that although the Pd crystallites on Pd/PIm/DNA nanowires decorate the PIm polymer, the major current pathway is through the polymer rather than the Pd.

Top-gated field-effect transistors have been created from bilayer epitaxial graphene samples that were grown on SiC substrates by a vacuum sublimation approach. A high-quality dielectric layer of Al 2 O 3 was grown by atomic layer deposition to function as the gate oxide, with an e-beam evaporated seed layer utilized to promote uniform growth of Al 2 O 3 over the graphene. Electrical characterization has been performed on these devices, and temperature-dependent measurements yielded a rise in the maximum transconductance and a significant shifting of the Dirac point as the operating temperature of the transistors was increased.

Ohmic contacts with low contact resistance, smooth surface morphology, and a well-defined edge profile are essential to ensure optimal device performance. Ohmic contacts often require annealing under vacuum at over 1000 °C, whilst high-κ dielectrics are usually annealed in O 2 rich ambient at temperatures of 800 °C or less, affecting the specific contact resistivity (ρ C ) and RMS surface roughness. Therefore, protection of the Ohmic contacts during the annealing of a high-κ dielectric layer is a key enabling step in the realisation of high performance MOSFET structures. In order to prevent damage during the high-κ formation, a passivation layer capable of protecting the contacts during annealing is required. In this work we have investigated the suitability of PECVD silicon nitride as a passivation layer to protect Ohmic contacts during high temperature, oxygen rich annealing.

Electroless metal deposition at DNA ‘template’ molecules in bulk solution, compared to previous surface-based routes, produces conductive, sub-10 nm, nanowires.

Electroless templating on DNA is established as a means to prepare high aspect ratio nanowires via aqueous reactions at room temperature. In this report we show how Pd nanowires with extremely small grain sizes (< 2 nm) can be prepared by reduction of PdCl4(2-) in the presence of lambda-DNA. In AFM images the wires are smooth and uniform in appearance, but the grain size estimated by the Scherrer treatment of line broadening in X-ray diffraction is less than the diameter of the wires from AFM (of order 10 nm). Electrical characterisation of single nanowires by conductive AFM shows ohmic behaviour, but with high contact resistances and a resistivity (-10(-2) omega cm) much higher than the bulk value for Pd metal (-10(-5) cm @ 20 degrees C). These observations can be accounted for by a model of the nanowire growth mechanism which naturally leads to the formation of a granular metal. Using a simple combing technique with control of the surface hydrophilicity, DNA-templated Pd nanowires have also been prepared as networks on an Si/SiO2 substrate. These networks are highly convenient for the preparation of two-terminal electronic sensors for the detection of hydrogen gas. The response of these hydrogen sensors is presented and a model of the sensor response in terms of the diffusion of hydrogen into the nanowires is described. The granular structure of the nanowires makes them relatively poor conductors, but they retain a useful sensitivity to hydrogen gas.

A comparison of radiated noise for Silicon and Silicon Carbide converters is presented. SiC JBS diodes were used in this evaluation to enable fast switching times, whilst minimizing the transistor junction temperature. Radiated electromagnetic-interference measurements showed the highest noise signature for the SiC JFET and lowest for the SiC MOSFET. The negative gate voltage requirement of the SiC MOSFET introduces up to 6 dBµV increase in radiated noise, due to the induced current in the high frequency resonant stray loop in the negative power plane of the gate drive. The SiC JFET and MOSFET have shown overall converter efficiencies of 96% and 95.5% respectively. This efficiency shows only a weak frequency dependence, in contrast to the CoolMOS/SiC JBS diode combination which demonstrated an efficiency drop from 95% to 92.5% when increasing the frequency from 100kHz to 250kHz.

w Oxygen functionalized epitaxial graphene (OFEG) sensors are demonstrated toward the sensing of polar chemical vapors at room temperature. The electrical characteristics of the sensor show an increase in resistance upon exposure to polar protic chemicals while the resistance decreased for polar aprotic vapors The average response and recovery times of the OFEG sensor to all analyte vapors are 10 and 100 s, respectively. In comparison, non-functionalized epitaxial graphene (NFEG) sensors show similar response times as OFEG, but with extremely long recovery rates in the range of similar to 1.5-2 hours. The dipole moment of the chemical is found to have a strong impact on the magnitude of the response for both OFEG and NFEG which increased with the increasing dipole moment from 2.0 D to 4.1 D. However, OFEG exhibits significantly higher sensitivity (twofold increase) to all polar chemicals over NFEG sensors. For example, exposing OFEG to n-methyl-2-pyrrolidone vapors produces a 45% change in resistance, in comparison to a 27% resistance change displayed by NFEG sensors. The noise spectral density of NFEG follows a typical 1/f dependence upon exposure to di-methylformamide vapors but with a lower change in noise from 1 x 10(-18)A(2)/Hz to 1 x 10(-17) A(2)/Hz at 1 Hz. In contrast, OFEG displays a unique 1/f(2) behavior at lower frequency range (1-10 Hz) with a significant change to the sensor noise from 3 x 10(-18)A(2)/Hz to 2 x 10(-15) A(2)/Hz.

In this work SiC-based MIS capacitors have been fabricated with different contact/high-k dielectric combinations and the temperature dependence of the characteristics have been examined in an N 2 ambient at temperatures between 323K and 673K. The structures utilise either a Pt or Pd catalytic gate contact and a TiO 2 or HfO 2 high-k dielectric, all of which are grown on a thin SiO 2 layer, thermally grown on the Si face of a 4H SiC epitaxial layer. The MIS capacitors have been studied in an N2 ambient between 323K and 673K and observations show that V FB reduces with increasing temperature. The majority of this variation is caused a reduction in the D it influencing the structures electrical characteristics, due to a shift in the semiconductors bulk potential, which is due to the lower V TH of SiC-based MOSFETs at high temperatures.

DNA strands have been used as templates for the self-assembly of smooth and conductive cuprous oxide (Cu2O) nanowires of diameter 12–23 nm and whose length is determined by the template (16 μm for λ-DNA). A combination of spectroscopic, diffraction and probe microscopy techniques showed that these nanowires comprise single crystallites of Cu2O bound to the DNA molecules which fused together over time in a process analogous to Ostwald ripening, but driven by the free energy of interaction with the template as well as the surface tension. Electrical characterization of the nanowires by a non-contact method, scanned conductance microscopy and by contact mode conductive AFM showed the wires are electrically conductive. The conductivity estimated from the AFM cross section and the zero-bias conductance in conductive AFM experiments was 2.2–3.3 S cm−1. These Cu2O nanowires are amongst the thinnest reported and show evidence of strong quantum confinement in electronic spectra.

MVP is a framework allowing websites to use diverse knowledge-based authentication schemes. One application is its use in conducting ecologically valid user studies of authentication under the same experimental conditions. We introduce MVP and its key characteristics, discuss several authentication schemes, and offer lessons learned from running 9 hybrid (lab/online) and 3 MTurk user studies over the last year.

In this work a Pt/HfO2/SiO2/SiC MIS capacitor is exposed in air at 400°C for 1000 hours, with its oxide capacitance, flatband voltage and density of interface traps being measured at various time intervals. After the structure has been shown to operate reliably for extensive periods of time at 400°C, the C-V characteristics of a device from the same fabrication batch are measured at 300°C in different concentrations of H2 and examined for sensitivity. The results demonstrate that gas sensitive MIS capacitors incorporating high-ĸ dielectrics, have the potential to operate at extreme temperatures for long periods of time. This makes them suitable for deployment in hostile conditions, where regular servicing may not be possible.

The commercialisation of Silicon Carbide devices and circuits require high performance, miniaturised devices which are energy efficient and can function on the limited power resources available in harsh environments. The high temperature Technology Computer Aided Design (TCAD) simulation model has been used to design and optimise a potential commercial device to meet the current challenges faced by Silicon Carbide technology. In this paper we report a new methodology to optimise the design of high temperature four terminal enhancement mode n- and p- JFETs for Complementary JFET (CJFET) logic.

This paper focuses on an ultra-sensitive H2 sensor fabricated using a time and cost-effective method. The sensor is comprised of Pd nanowires fabricated using λ-DNA templates. The morphology and the electrical characterisation of the metalized DNA nanowires (diameter = 5–45nm) were investigated by AFM and conductive AFM (cAFM). The conductivity of a single Pd-DNA nanowire, 127 Scm−1 was substantially lower than that of bulk Pd (9.5×104 Scm−1). However, the sensor shows high sensitivity towards hydrogen evaluated by recording the change in the resistance on exposure to cycles of different concentrations of H2 in N2 flow at 330K. The sensor showed a reversible response to H2 concentrations between 2300 – 12500 ppm and a response time of ∼85 s. These results indicate that using DNA as a template is a promising method for the fabrication of low cost and rapid response sensors.

Trenched implanted vertical JFETs (TI-VJFETs) with self-aligned gate and source contacts were fabricated on commercial 4H-SiC epitaxial wafers. Gate regions were formed by aluminium implantation through the same silicon oxide mask which was used for etching mesa-structures. Self-aligned nickel silicide source and gate contacts were formed using a silicon oxide spacer formed on mesa-structure sidewalls by anisotropic thermal oxidation of silicon carbide followed by anisotropic reactive ion etching of oxide. Fabricated normally-on 4H-SiC TI-VJFETs demonstrated low gate leakage currents and blocking voltages exceeding 200 V.

3.3 kV rated 4H-SiC diodes with nickel monosilicide Schottky contacts and 2-zone JTE regions were fabricated on commercial epitaxial wafers having a 34 m thick blocking layer with donor concentration of 2.2×1015 cm-3. The diodes were fabricated with and without additional field stop rings to investigate the impact of practically realizable stopper rings on the diode blocking characteristics. The field stop ring was formed by reactive ion etching of heavily doped epitaxial capping layer. The diodes with field stop rings demonstrated significantly higher yield and reduction of reverse leakage current. The diodes demonstrated blocking voltages in excess of 4.0 kV and very low change of leakage current at ambient temperatures up to 200 °C.

The variation in device process parameters is a core issue in the realisation of complex SiC logic for extreme environments. Factorial design was used to study the effect of variation in four key process parameters on the threshold voltage of an n-channel lateral JFET. Each parameter is simultaneously varied by +/-10% from the default value and the individual and combined effects were calculated at 300, 600 and 1000K. Consequently, we show how these variations in device parameters degrade the threshold voltage, VI, and, hence, the noise margin of logic inverter.