Good Electrical Connection Research Articles

Direct and Large-Area Growth of One-Dimensional ZnO Nanostructures from and on a Brass Substrate

A convenient method for the direct and large-area growth of one-dimensional (1-D) ZnO nanostructures on a conductive brass substrate has been developed, consisting of thermal oxidation of a Cu0.66Zn0.34 alloy foil in the presence of oxygen. Various 1-D nanostructures such as nanowires, nanobelts, nanocombs, and nanosheets have been in situ grown on the brass substrate under different reaction temperatures and characterized by means of X-ray diffraction, electron microscopy, and X-ray photoelectron spectroscopy. In this preparation, the Cu0.66Zn0.34 alloy foil functions as both Zn source and substrate for the growth of 1-D ZnO nanostructures; thus, the synthesis and assembly of ZnO nanostructures on a metallic substrate is accomplished in one step, and the naturally good adhesion or electrical connection between the ZnO nanostructures and the conductive substrate has been realized. This approach could prepare ZnO nanostructures on a brass substrate without size limitations. Such a configuration of product ...

Carbon Nanotubes Grown on Stainless Steel to Form Plate and Probe Electrodes for Chemical/Biological Sensing

This paper describes the fabrication and evaluation of carbon nanotube (CNT) electrodes grown on stainless steel (SS) plate and wire for electrochemical sensor applications. Multi-wall carbon nanotubes with different diameters were grown on the SS plate and wire by chemical vapor deposition from an ethylene precursor. The SS provides a good electrical and mechanical connection to the CNT, and the SS is a tough substrate. The SS part of the electrode was electrically insulated from the analyte so that only the CNT were active in sensing. Cyclic voltammetry for the reduction of 6 mM K3Fe(CN)6 in a 1.0 M KNO3 supporting electrolyte was performed to examine the redox behavior of the CNT-SS electrode. The cyclic voltammograms showed sigmoidal-like shapes, indicating that mass transport around the electrodes is dominated by radial diffusion. Based on the cyclic voltammograms, the effective area of the CNT-SS electrodes and the number of individual CNTs were estimated. These results indicate that the CNT-SS plate and wire electrodes are good candidates to develop practical in vivo biosensors.

Towards the silicon nanowire-based sensor for intracellular biochemical detection

A microneedle sensor platform with integrated silicon nanowire tip was developed for intracellular biochemical detection. Because of the virtue of miniaturized size and high sensitivity, this sensor has a great potential for studying individual cell or localized bioenvironment by revealing the pH level and/or enzyme activities. The fabrication of the microneedle sensor was primarily based on conventional silicon processing, where a silicon-on-insulator (SOI) wafer with 50 nm thick (1 0 0) p-type Si device layer was used as the substrate. The silicon nanowires of 50 nm height and 50–100 nm width were created by electron beam (E-beam) lithography on the tip of microneedle with good electrical connection to the contact pads for convenient electrical measurement. A three layer structure with base, support cantilever, and needle tip was designed to ensure convenient handling of sensors and minimize the invasive penetration into biological cells. In this paper, we demonstrate a preliminary assessment of this novel intracellular sensor with electrical conductance measurement under different pH levels. It is expected that this sensor with proper chemical modification will enable localized biochemical sensing within biological cells, such as neurotransmitter activities during the synaptic communication between neuron cells.

Embedded Nanowire Network Growth and Node Device Fabrication for GaAs-Based High-Density Hexagonal Binary Decision Diagram Quantum Circuits

The basic feasibility of constructing hexagonal binary decision diagram (BDD) quantum circuits on GaAs-based selectively grown (SG) nanowires was investigated from viewpoints of electrical connections through embedded nanowires and electrical uniformity of devices formed on nanowires. For this, <110>- and <510>-oriented nanowires and hexagonal network structures combining these nanowires were formed on (001) GaAs substrates by selective molecular beam epitaxy (MBE) growth. The width and vertical position of the nanowires could be controlled by growth conditions for both <110>- and <510>-directions. By current–voltage (I–V) measurements, good electrical connection was confirmed at the node point where vertical alignment of embedded GaAs nanowire pieces was found to be important. SG quantum wire (QWR) switches formed on the nanowires showed good gate control over a wide temperature range with clear conductance quantization at low temperatures. Good device uniformities were obtained on the test chips, providing a good prospect for future integration. BDD node devices using SG QWR switches showed clear path switching characteristics. Estimated power-delay product values were very small, confirming the feasibility of ultra low-power operation of future circuits.

Processability and reliability of nonconductive adhesives (NCAs) in fine-pitch chip-on-flex applications

The use of NCAs to form direct contact interconnections between chip bumps and substrate pads have become a viable option in interconnection technology for fine-pitch applications. However, the primary concerns with NCAs are their long-term reliability, stability, and consistent electrical performance in particulate interconnections. Results of assembly process studies and environmental testing using NCAs on flexible substrates are analyzed and discussed herein. An extensive design experiment was performed to determine which process parameters were critical in obtaining good electrical connections. A reliability evaluation of NCAs for flexible substrate applications was carried out to gain more insight into the failure mechanisms of this type of interconnect. Pressure cooker test results showed that failures occurring in NCA joints are primarily due to moisture absorption, which could lead to interfacial delamination at the substrate/adhesive interface, accompanied by hygroscopic swelling. NCAs with lower coefficients of thermal expansion also exhibited better contact resistance stability during high-temperature storage tests.

Use of laser drilling in the manufacture of organic inverter circuits

Inverter circuits have been made by connecting two high-quality pentacene field-effect transistors. A uniform and pinhole-free 900 nm thick polyimide gate-insulating layer was formed on a flexible polyimide film with gold gate electrodes and partially removed by using a CO2 laser drilling machine to make via holes and contact holes. Subsequent evaporation of the gold layer results in good electrical connection with a gold gate layer underneath the gate-insulating layer. By optimization of the settings of the CO2 laser drilling machine, contact resistance can be reduced to as low as 3 ohms for 180 microm square electrodes. No degradation of the transport properties of the organic transistors was observed after the laser-drilling process. This study demonstrates the feasibility of using the laser drilling process for implementation of organic transistors in integrated circuits on flexible polymer films.

Fabrication of Terahertz Frequency Phonon Cooled HEB Mixers

We have successfully fabricated NbTiN phonon-cooled, hot-electron bolometers (HEBs) on silicon-on-insulator (SOI) substrates for use in terahertz-frequency waveguide mixers. At these frequencies our technology offers three significant advantages over the more common approach of using thin quartz substrates. Firstly, the SOI chips are more rugged than quartz, which become very fragile at the required thickness (<20 microns). Secondly, the outline of the chips is defined lithographically so that they can be given a nonrectangular shape that may be required for more complicated circuits. Thirdly, freestanding gold beam-leads are used to hold the chip in place in the waveguide block and to make good electrical connections at DC, IF (intermediate frequency) and signal frequencies. The SOI wafer is a 6 /spl mu/m thick Si layer bonded to a 400 /spl mu/m thick oxidized Silicon "handle" wafer. The HEBs and gold beam-leads are fabricated on front side of the SOI wafer. After processing the front side, the handle wafer is removed and the 6 /spl mu/m Si layer is patterned and etched to complete the device. Mixer measurements have been made with such devices at a signal frequency of 19 GHz, giving an IF bandwidth of about 1.4 GHz (under conditions that maximize low-frequency conversion efficiency). This bandwidth is close to that measured with similar devices on thicker silicon and on quartz.

Investigation of diamond coatings on titanium substrates for electrochemical applications

Diamond coated titanium electrodes show outstanding properties in alkaline electrolytes as they are corrosion resistant by forming stable TiO 2 layers. This quality is of decisive importance for this kind of application. Boron doped diamond layers were deposited on Ti sheets by the hot-filament method, using Triethylboron (B(C 2H 5) 3) as a boron source to produce electrodes for electrochemical applications. Ratios of (B(C 2H 5) 3):CH 4 were varied between 0 and 10 000 ppm and silicon was used as a reference material. Diamond growth on metallic titanium is proceeded by the formation of an intermediate TiC layer, which ensures a good electrical connection between the Ti substrate and the diamond but leads to poor adhesion of the layers. Additionally, boron influences the interlayer formation due to the formation of borides or carbo-borides. Correlations between diamond layer adhesion and boron addition during diamond deposition can be shown. To examine the electrochemical properties of diamond layers with various morphologies, cyclic voltammetry measurements were carried out in different solutions (0.1 N H 2SO 4, 6 N NaOH). Thereby large potential windows up to 4.7 V could be observed. It could be shown that boron has a positive influence on diamond deposition on Ti substrates in terms of better adhesion corresponding with a very large potential window in acid as well as basic solutions.

Electrical and magnetic properties of conductive Cu-based coated conductors

The development of YBa2Cu3O7−δ (YBCO)-based coated conductors for electric power applications will require electrical and thermal stabilization of the high-temperature superconducting (HTS) coating. In addition, nonmagnetic tape substrates are an important factor in order to reduce the ferromagnetic hysteresis energy loss in ac applications. We report progress toward a conductive buffer layer architecture on biaxially textured nonmagnetic Cu tapes to electrically couple the HTS layer to the underlying metal substrate. A protective Ni overlayer, followed by a single buffer layer of La0.7Sr0.3MnO3, was employed to avoid Cu diffusion and to improve oxidation resistance of the substrate. Property characterizations of YBCO films on short prototype samples revealed self-field critical current density (Jc) values exceeding 2×106 A/cm2 at 77 K and good electrical connectivity. Magnetic hysteretic loss due to Ni overlayer was also investigated.

La 0.7 Sr 0.3 MnO 3 : A single, conductive-oxide buffer layer for the development of YBa2Cu3O7−δ coated conductors

Coated conductor applications in power technologies require stabilization of the high-temperature superconducting (HTS) layers against thermal runaway. Conductive La0.7Sr0.3MnO3 (LSMO) has been epitaxially grown on biaxially textured Ni substrates as a single buffer layer. The subsequent epitaxial growth of YBa2Cu3O7−δ (YBCO) coatings by pulsed laser deposition yielded self-field critical current densities (Jc) of 0.5×106 A/cm2 at 77 K, and provided good electrical connectivity over the entire structure (HTS+conductive-buffer+metal substrate). Property characterizations of YBCO/LSMO/Ni architecture revealed excellent crystallographic and morphological properties. These results have demonstrated that LSMO, used as a single, conductive buffer layer, may offer potential for use in fully stabilized YBCO coated conductors.

Growth and characterization of conductive SrRuO3 and LaNiO3 multilayers on textured Ni tapes for high-Jc Yba2Cu3O7–delta; coated conductors

Power applications of high-temperature superconducting (HTS) coated conductors will require stabilization against thermal runaway. We have developed conductive buffer layers to electrically couple the HTS layer to the underlying metal substrate. The structure comprises the layer sequence of SrRuO3 (SRO) on LaNiO3 (LNO) on biaxially textured Ni substrates. We report baseline investigations of compatibility of SRO/LNO multilayer structure with processing of Yba2Cu3O7−δ (YBCO) and demonstrate biaxially textured YBCO films on conductively buffered Ni tapes. These YBCO coatings exhibit self-field Jc values as high as 1.3 × 106 A/cm2 at 77 K, and the entire structure (HTS + conductive buffers + metal substrate) shows good electrical connectivity. These results demonstrate that SRO/LNO buffer layers may provide a basis for stabilized coated conductors.

Effect of electrochemically oxidized carbon colloid on lead acid batteries

An aqueous solution of carbon colloid was prepared by electrochemical oxidation of a graphite anode. It was found that the addition of this colloid into the electrolyte of lead acid batteries enhanced the charge–discharge capacity and extended life. The mechanism for this could be as follows: As a result of electrochemical oxidation the surface of the carbon particles is subjected to a chemical modification, and is endowed with hydrophilic groups such as carboxyl. This was confirmed with ESCA spectroscopy. When the carbon colloid is added to an electrolyte in a lead acid battery, the cathode (PbO 2) is electrochemically doped with the carbon particles. This is supported by the results of voltammetric and optical absorption spectroscopic studies. Since PbO 2 is a semiconductor and is used in a granular form, some of the particles probably do not have good electrical connection, and are not fully utilized. It is expected that doped carbon particles could provide electrical connection to non-utilized PbO 2 particles, which enhances the charge–discharge capacity and extends the life of lead acid batteries.

Correction to "A Bioelectric Inverse Imaging Technique Based On Surface Laplacians"

IV. CONCLUSION The perforated Si-based microelectrode arrays described in this work are robust, easy to handle and show no noticeable deterioration after repeated use. The three-dimensionality of the Pt microelectrodes allows good electrical connections with nervous tissue as well as the possibility to perform measurements on membrane-tissue sandwiches to be achieved. Specifically developed for the organotypic slice cultures, these arrays represent a powerful tool for monitoring electrophysiological activity of slice cultures over extended periods of time, for pharmacological and toxicological studies. ACKNOWLEDGMENT

Coated carbon fibres and their composites with tin-lead matrix

The white metal, or Babbitt, bearing metal, based on lead or tin, has excellent frictional properties. It also possesses a number of other important properties such as embeddabitity, conformability and corrosion resistance. However, it is mechanically weak. Tin-lead alloys are most commonly used for solders and bearings. Solder preforms are used to joint various parts of an electronic package. Because the thermal expansion coefficient of a solder is in general much higher than that of a substrate, the solder joint suffers from poor resistance to thermal fatigue. Thus, there is a need for a solder with a low thermal expansion. On the other hand, if tin-lead alloys can be made stronger, they can carry greater bearing loads and hence offer the possibility of reduction in overall bearing size for a given application. Composite materials can be tailored to exhibit a chosen thermal expansion coefficient, as the filler species and the filler volume fraction can be suitably chosen. For a low thermal expansion composite, the filler must have a low thermal expansion coefficient. Moreover, the filler should be a good electrical conductor because the soldered joint then serves as a good electrical connection as well as mechanical connection. It is also required to be a good thermal conductor to enable heat dissipation from the electronic package. In addition, the filler should have good mechanical properties in order to strengthen the tin-lead alloy. One of the suggested means of strengthening bearings involves the incorporation of carbon fibres, thus using the fibres as a reinforceing agent and possibly also as a lubricating agent by a virtue of its graphite nature. Carbon fibres also have near-zero thermal expansion coefficient. Furthermore, carbon fibres are widely available in continuous form, which makes them more effective in lowering the thermal expansion coefficient of the composite and which prevents fibre distribution from becoming nonuniform after remelting and solidification [2]. Carbon fibre reinforced tin-lead alloys have been fabricated by liquid metal infiltration [1, 2] and by investment casting for fundamental process studies [3, 4]. It is well known that carbon fibres are not wetted by liquid lead or tin. In order to produce good wetting and prevent chemical reaction between carbon fibres and metal matrix during synthesis of composites, fibres have often been coated with refractory or metal materials [4-7]. In the previous studies [1-4], carbon fibres were electroplated with copper or nickel in order to ensure good wetting of the fibres by the alloy, but the weak bonding

Laser bonded n-GaAs/p-GaSb heterojunction intercell Ohmic contact

An n-GaAs/p-GaSb heterojunction intercell Ohmic contact (IOC) has been formed by a laser bonding procedure. Resistance per unit area of 5×10−3 Ω-cm2 has been obtained as an upper limit. This IOC is able to provide sufficiently good electrical connection between two adjacent subcells of a monolithic multicolor solar converter operating at several hundred suns concentration with the insignificant I2R loss.

The Good Connection

This article illustrates and details the proper and safe way to make a good electrical connection either by splicing wires together or attaching them at a pump control box.

Omnitrode: A simple cannula for chemical and bipolar electrical stimulation

A compact and easily built cannula that can be used for both chemical and bipolar electrical stimulation at the same brain site is described. This reusable cannula is made from inexpensive biologically inactive materials. It is small in size and requires no machining yet provides gold-plated contacts for good electrical connections. It is useful for both dry and liquid microinjection of chemicals. The cannula is also recommended for multiple implantations.