Process-controlled staggered ambipolar amorphous-silicon thin-filmtransistor

The results of measurements performed on amorphous-silicon thin-film transistors (TFTs) are presented and interpreted. Both unipolar and ambipolar effect TFTs are obtained in the experiments. Whether they possess unipolar or ambipolar characteristics is controlled by the interface properties between gate insulator and amorphous silicon. With the different compositions of hybrid gate insulators, the devices show different I-V characteristics. A simple method for estimating film parameters of amorphous silicon and device parameters of the TFTs is developed. The characteristic energy of an amorphous-silicon film is obtained from the slope of the ratio of saturation current to transconductance. Threshold voltages and flatband voltages of the TFTs can also be obtained using this method     

Optimization of the forming conditions of the solid-state interface in the Li-ion batteries

We optimized the forming conditions of Li-ion batteries from the standpoint of the stability of the solid-state interface (SEI) on the surface of graphite. The optimization processes were focused on the initial two cycles of the Li/graphite half-cell in terms of the current density and the temperature. We evaluated the stability of the SEI from two aspects: (1) self-delithiation at 60 °C of the lithium intercalation compound, which reflects storage stability of the SEI and (2) cycling performance of the Li/graphite cell, which reflects cycling stability of the SEI. It was observed that the low current density and the low temperature favored increasing effectiveness of the SEI formation, and resulted in formation of a stable SEI. However, the SEI formed under such conditions had relatively high impedance. That is, there was a contradictory relationship between the ionic conductivity and the stability of the SEI. Based on the graphite and electrolyte used in this work, we found that the optimum conditions for the formation of the SEI were at the current densities of 10–20 mA/g and at the temperatures of 20–35 °C.     

ANODIC REACTIONS OF PROPYLENE IN THE BROMIDE AQUEOUS SOLUTIONS

The formation of propylene oxide actually occurred in the homogeneous bromide aqueous solutions for the anodic oxidation of propylene. It was found that the selectivity was very high and the current yield was mainly affected by the pH values and the spaces between the electrodes. The effect of pH values on the distributions of different types of ions in the solution was also described.     

Modeling and Optimization of Printed Spiral Coils in Air, Saline, and Muscle Tissue Environments

Printed spiral coils (PSCs) are viable candidates for near-field wireless power transmission to the next generation of high-performance neuroprosthetic devices with extreme size constraints, which will target intraocular and intracranial spaces. Optimizing the PSC geometries to maximize the power transfer efficiency of the wireless link is imperative to reduce the size of the external energy source, heating of the tissue, and interference with other devices. Implantable devices need to be hermetically sealed in biocompatible materials and placed in a conductive environment with high permittivity (tissue), which can affect the PSC characteristics. We have constructed a detailed model that includes the effects of the surrounding environment on the PSC parasitic components and eventually on the power transfer efficiency. We have combined this model with an iterative design method that starts with a set of realistic design constraints and ends with the optimal PSC geometries. We applied our design methodology to optimize the wireless link of a 1-cm ² implantable device example, operating at 13.56 MHz. Measurement results showed that optimized PSC pairs, coated with 0.3 mm of silicone, achieved 72.2%, 51.8%, and 30.8% efficiencies at a face-to-face relative distance of 10 mm in air, saline, and muscle, respectively. The PSC, which was optimized for air, could only bear 40.8% and 21.8% efficiencies in saline and muscle, respectively, showing that by including the PSC tissue environment in the design process the result can be more than a 9% improvement in the power transfer efficiency.     

Investigation of dielectric properties of polymer laminates withpolyvinylidene fluoride

The breakdown field strength of polymer laminates consisting of polymer base films coated with a thin layer of polyvinylidene fluoride (PVDF) was investigated. The spin coating technique was used to make a layer of PVDF film. It was found that the dc breakdown field strength could be increased by as much as 18% by applying a very thin coating. The breakdown field strength was insensitive to the thickness of the polymer base films and the thickness of the PVDF coating within the thickness range used in the experiment. The effect of the coating on the permittivity and dissipation factor of polymer films over a wide frequency range was determined. Possible mechanisms for the enhancement of breakdown field strength have been discussed     

Optimization of Data Coils in a Multiband Wireless Link for Neuroprosthetic Implantable Devices

We have presented the design methodology along with detailed simulation and measurement results for optimizing a multiband transcutaneous wireless link for high-performance implantable neuroprosthetic devices. We have utilized three individual carrier signals and coil/antenna pairs for power transmission, forward data transmission from outside into the body, and back telemetry in the opposite direction. Power is transmitted at 13.56 MHz through a pair of printed spiral coils (PSCs) facing each other. Two different designs have been evaluated for forward data coils, both of which help to minimize power carrier interference in the received data carrier. One is a pair of perpendicular coils that are wound across the diameter of the power PSCs. The other design is a pair of planar figure-8 coils that are in the same plane as the power PSCs. We have compared the robustness of each design against horizontal misalignments and rotations in different directions. Simulation and measurements are also conducted on a miniature spiral antenna, designed to operate with impulse-radio ultra-wideband (IR-UWB) circuitry for back telemetry.     

Determination of surface area of carbon-black by simple cyclic-voltammetry measurements in aqueous H2SO4

Determination of the surface area of commercial carbon-black (CB) by cyclic-voltammetry (CV) measurements of the electrochemical double-layer charge (Q) in aqueous sulfuric acid was investigated. Various factors that affect the Q value associated with CB, including: the presence of redox-reversible function-groups, the binders used for the formation of thin-film CB electrodes, the scan rates of the CV measurement, H₂SO₄ electrolyte concentration and the volume of air contained in the pores of the CB samples were examined. Conditions for measuring Q without interference from these factors were investigated and the data derived, without interference, was found to correlate well with the surface area of the CB. The results show that the total Brunauer–Emmett–Teller (BET) surface area shows good correlation (R² = 0.993) with the Q value corresponding to a full charge/discharge of the CB (Q₀), obtained by extrapolation at a zero scan rate; additionally, the CB micropore surface area (diameter < 2 nm) shows good linear correlation with the Q deficiency (Q₀–Q), measured at 5 mV s^?1 (R² = 0.998).     

Growth of GaAs by vacuum atomic layer epitaxy using tertiarybutylarsine

We report the results of GaAs grown by vacuum atomic layer epitaxy using trimethylgallium (TMGa) and tertiarybutylarsine (TBAs) as the group III and V sources. The growth rate saturates at one monolayer per cycle for a wide range of growth parameters. The temperature window for monolayer growth is as wide as 70°C. All the films are p-type with the carrier concentration depending on the exposure conditions of TMGa and TBAs.     

A Computerized Test System for Communications Equipment Subassemblies

This paper describes an automatic test system for factory testing of telephone carrier equipment channel units. The system is intended for high volume subassemblies such as those found in pulse-code-modulation carrier systems where, typically, there are 24 units in each terminal. With the greater availability of minicomputers and digitally programmable instruments, a system is feasible at moderate cost. The system described uses a low-cost self-contained eight-bit minicomputer as the test sequence controller. Control information is transmitted to and from the various instruments by way of a data input-output buffer. A reed contact switching matrix is used to interconnect commercial equipment that is used to generate inputs and measure results. The resulting system is capable of making up to 100 functional tests on a channel unit in less than one minute. Significant savings have been possible in testing time and labor cost. Also, equipment reliability is improved because of uniform testing methods.     

Catalytic effects of the silver ion on the indirect electrochemical oxidation of toluene to benzaldehyde using Ce3+/Ce4+ as mediator

The catalytic effects of the silver ion on toluene oxidation by Ce⁴⁺ as well as the anodic generation of Ce⁴⁺ were investigated. The rates of toluene oxidation were first order with respect to both Ag⁺ and Ce⁴⁺. Argentic oxides formed on the surface of the platinum anode when Ag⁺ was present in the anolyte, which increased the activity of the electrode. About 3×10^–3M of Ag⁺ was needed to obtain maximum current efficiency.