External Electrical Connections Research Articles

Flexible IGZO TFT Technology for Shift Register Drivers

AbstractActive sensing matrices play a pivotal role in various electronic devices, including optical and X‐ray imaging arrays, electronic skins, and artificial tactile arrays, among others. These matrices function through a thin‐film active switching mechanism, allowing for the scanning of rows and columns by external circuitry to read the sensory signals of individual pixels. Recently, indium–gallium‐zinc oxide thin‐film transistors (IGZO TFTs) have emerged as highly promising technology in the realm of flexible electronics. They enable the large‐scale integration of functional circuits on flexible substrates. Shift registers are commonly employed as peripheral scanning circuits to sequentially address active‐matrix arrays. To enhance system compactness and minimize external electrical connections, it is imperative to seamlessly integrate shift registers within the active matrices. However, contemporary flexible IGZO‐based shift registers suffer from high operating voltages and low frequencies, which constrain their applicability in high‐performance flexible sensors and displays. In response to this challenge, a breakthrough is presented in the form of low‐voltage, high‐frequency bootstrap shift registers implemented with flexible IGZO technology. The approach involves utilizing SU‐8 buffered polyimide (PI) polymer foils as substrates. These foils boast an exceptional level of surface smoothness, significantly increasing the yield and performance of electronic components, including vias, IGZO TFTs, and capacitors used in the shift register circuitry. Additionally, HfO2/Al2O3/HfO2 sandwich structures are employed as high‐k dielectric layers to reduce the operational voltage. Thanks to the innovative circuit design and optimized fabrication methods, the 16‐stage shift register can operate at just 1.8 V with a frequency of 15 kHz. This breakthrough promises to have a profound impact on a wide range of applications for driving flexible active‐matrix electronic systems.

Highly efficient rechargeable Zn-air batteries based on hybrid CNT-grafted, Co/CoS2-Fe embedded, Nitrogen-doped porous carbon Nano-frameworks

Catalysts with embedded and functionalized elements used for the effective control of oxygen-reduction (ORRs) and oxygen-evolution reactions (OERs) are the key to developing high-performance rechargeable Zn–air batteries (ZABs). Here, carbon nanotube-grafted, Co–Fe embedded, nitrogen-doped porous carbon nano-frameworks (CNT–Co–Fe/NC) were synthesized through the carbonization of Fe-doped zeolitic imidazolate frameworks and vulcanization of the CNT–Co–Fe/NC to form CNT–CoS2–Fe/NC. The CNT–CoS2–Fe/NC exhibited a superior OER performance with an overpotential of only 1.637 mV at a current density of 10 mA/cm2 and a Tafel slope of 197 mV/dec (which, for RuO2, is 112 mV/dec), whereas the CNT–Co–Fe/NC showed an excellent ORR performance with a Tafel slope of 71 mV/dec (which, for 20 wt% Pt/C, is 91 mV/dec). A ZAB was developed with a hybrid catalyst of 50 wt% CNT–Co–Fe/NC and 50 wt% CNT–CoS2–Fe/NC in the cathode, and it achieved an excellent specific discharge capacity of 814 mAh/g at 50 mA/cm2, high power density of 245 mW/cm2, and outstanding cycle stability of over 1800 cycles (300 h) at 10 mA/cm2 with a very high retention of 95% and small potential gap of 0.68 V, compared to the corresponding values of 803.7 mAh/g, 215.3 mW/cm2, 900 cycles: retention 92%, and potential gap 0.837 V for 150 h for the ZAB with a hybrid catalyst of Pt/C + RuO2. It is hypothesized that the ZAB with the novel hybrid catalyst exhibits its excellent catalytic activity and durability as a result of the synergistic effect of the catalyst’s embedded heteroatoms and nitrogen–metal/carbon framework that enhances the ORR/OER performance, porous carbon nano-framework that enables rapid diffusion and electrical conduction, and carbon nanotubes that complete the external electrical connection between the catalysts.

Laser Patterned Electroplated Copper Contacts for Interdigitated Back Contact Silicon Solar Cells

Metallization of interdigitated back contacts for Si-based solar cells (IBC), where both the n- and p-contacts are processed on the rear side of the device, currently requires costly and labor-intensive masking, photolithography, and/or screen printing approaches, which are difficult for scale-up to high-throughput high-volume manufacturing. Electrodeposition (ED) offers a low cost, scalable, and selective approach for IBC metallization, but is potentially complicated by the close geometry of the contacts and the need for simultaneous plating to both contacts to achieve high processing throughput. Direct laser patterning of a thin seed metal film offers a fast single-step process for defining contact areas, reducing both device handling and chemical use, and allows simple variation of contact design to implement external electrical connections for ED, as well as rapid testing of alternative pattern dimensions and the subsequent effects on device performance. A simple and flexible direct laser scribing approach for processing of IBCs through patterning of thin Ni seed layers prior to Cu electroplating will be presented.IBC patterns were laser-scribed on blanket evaporated Ni seed layers on a-SiNx:H-coated textured-Si wafers (Ni/a-SiNx:H/Si) prior to plating. Patterning was carried out at optimum laser powers to achieve electrical isolation of the Ni contacts. Pattern designs, with 12 mm long n- and p-fingers of 400 and 1200 µm in width, respectively, were fabricated to include tabs for external contacting for ED (Fig. 1a). Contact patterns were prepared using either double-pass-focused or single-pass-defocused laser conditions during ablation. Samples processed with either single (Fig. 1b) or double (Fig. 1c) laser passes show well-defined ~100 µm cuts, however, those patterned with the latter condition showed a ~20 µm laser-induced trench along the center of all scribe lines, due to overlap of the beam paths, and which was not observed for patterns processed with a single pass. Plating conditions from acidified CuSO4-based baths were optimized for deposit reproducibility, uniformity, and adhesion on substrates of non-patterned thin evaporated Ni seed layers on 150 µm textured-Si wafers. Films of growth rate ~0.1 µm/min were achieved, with contact resistance (RC) ~5 mΩ.cm2, and excellent adhesion, enduring pull tests of >5 N where the Si wafer broke before any peeling of the Cu layer.With plating to laser-patterned IBC substrates, significant Cu features grow from the edges of the laser cuts (Fig. 1d), eventually shorting the fingers and leading to unwanted deposition outside of the contact areas. Shorting was not observed with plating to IBC Ni seed patterns that had been evaporated through a shadow mask, suggesting residual conductive phases in the scribes are responsible for the growth of the shorts. Brief chemical etches were carried out after scribing to remove residues and, following Cu plating, etched samples showed attenuated growths into the laser scribes with the contacts remaining electrically isolated. However, for single laser pass samples, ~40 µm wide parasitically-plated Cu stripes (Fig. 1e) were observed along the center of the laser cuts throughout the scribed pattern. Energy-dispersive x-ray spectroscopy (EDS) mapping confirmed the stripe consists of discrete Cu islands, isolated from the growing layer, that eventually coalesce during plating (Fig. 1f). This Cu-stripe feature was not observed for double laser pass samples, indicating differences in properties of the scribes with the different laser patterning conditions.The formation of the Cu-stripe is postulated to be the result of laser ablation and chemical etch damage to the insulating a-SiNx:H layer that opens pinholes to the more conductive c-Si wafer (Fig. 1g). These higher conductivity points produce localized conduits of enhanced current density, sufficient to nucleate Cu, and allow subsequent rapid growth of islands. In contrast, with plating to double pass processed samples, the more extensive laser damage to the a-SiNx:H layer exposes a significantly larger area of the Si wafer, which results in lower current densities insufficient to nucleate Cu. These observed effects of damage to both underlying layers and to growth habits of subsequent films, highlight the need for careful optimization and control of laser conditions during fabrication of photovoltaic devices.Front-junction Si-based solar cells with Al back contacts were etched and re-contacted with ED Cu to IBC-patterned Ni seed layers that had been evaporated through a shadow mask. Device performance showed little change, maintaining ~18% efficiency, with decreased device series resistance through improved RC. These results confirm ED Cu as a feasible and industrially-relevant approach for processing high quality metal contacts for Si-based solar cells. Figure 1

Development of an active high-density transverse intrafascicular micro-electrode probe

In this work, the development of an active high-density transverse intrafascicular micro-electrode (hd-TIME) probe to interface with the peripheral nervous system is presented. The TIME approach is combined with an active probe chip, resulting in improved selectivity and excellent signal-to-noise ratio. The integrated multiplexing capabilities reduce the number of external electrical connections and facilitate the positioning of the probe during implantation, as the most interesting electrodes of the electrode array can be selected after implantation. The probe chip is packaged using thin-film manufacturing techniques to allow for a minimally invasive electronic package. Special attention is paid to the miniaturization, the mechanical flexibility and the hermetic encapsulation of the device. A customized probe chip was designed and packaged using a flexible, implantable thin electronic package (FITEP) process platform. The platform is specifically developed for making slim, ultra-compliant, implantable complementary metal-oxide-semiconductor based electronic devices. Multilayer stacks of polyimide films and HfO2/Al2O3/HfO2 layers deposited via atomic layer deposition act as bidirectional diffusion barriers and are key to the hermetic encapsulation. Their efficacy was demonstrated both by water vapor transmission rate tests and accelerated immersion tests in phosphate buffered saline at 60 °C. Using the hd-TIME probe, an innovative implantation method is developed to prevent the fascicles from moving away when the epineurium is pierced. In addition, by transversally implanting the hd-TIME probe in the proximal sciatic nerve of a rat, selective activation within the nerve was demonstrated. The FITEP process platform can be applied to a broader range of integrated circuits and can be considered as an enabler for other biomedical applications.

A bipolar passive DMFC stack for portable applications

A bipolar passive direct methanol fuel cell (DMFC) stack for portable applications is designed, fabricated and tested. Stainless steel sheet is chosen to fabricate the current collectors by using the traditional wire cutting and laser beam cutting techniques. A 3.5 μm Au layer is deposited on the current collectors using electroplating method to prevent electrochemical corrosion. A novel design of the current collectors is proposed, which makes internal and external electrical connections be seamlessly integrated so that the resistance loss can be reduced. The maximum power density of the passive stack is 18.7 mW cm−2 at 3 M methanol concentration. The effect of the passive DMFC stack placement mode is studied. The results indicate that the passive DMFC stack in mode B (vertical cathode air channels) exhibits better and more stable performance than its counterpart in mode A (parallel cathode air channels) in discharging of high currents. Finally, the bipolar passive DMFC stack proves its good performance in powering the experimental fan in 100 days while performance deterioration behaviour is also detected.

Meta-atom microfluidic sensor for measurement of dielectric properties of liquids

High sensitivity microwave frequency microfluidic sensing is gaining popularity in chemical and biosensing applications for evaluating the dielectric properties of liquid samples. Here, we show that a tiny microfluidic channel positioned in the gaps of a dual-gap meta-atom split-ring resonator can exploit the electric field sensitivity to predict the dielectric properties of liquid samples. Employing an empirical relation between resonant characteristics of the fabricated sensor and the complex permittivity of water-ethanol or water-methanol mixtures produces good congruence to standardized values from the literature. This microfluidic sensor offers a potential lab-on-chip solution for liquid dielectric characterization without external electrical connections.

Wireless Corrosion Sensors: Review and Status

WIRELESS CORROSION SENSORS: Review and StatusThe traditional methods to study corrosion of metallic materials in occluded environments involve external electrical connections to electrochemical instrumentation, and they are intrusive. Advances in microelectronics have made possible new sensors based on RFID and wireless interrogation [1] “Wired” connections could be optical fibers used for spectroscopic detection of species, or for corrosion of metal films for example [4,5]. Publications that discuss probes and sensors with “wired” connections for corrosion are in references [6-16]. Most traditional monitoring techniques characterize the behavior of macroscopic samples either exposed to simulated conditions or exposed in service conditions. Broomfield, et al.[17] recently reviewed techniques for studying corrosion degradation: (1) linear polarization resistance (LPR); (2) critical threshold concentrations of damaging species (e.g. chloride ions, or pH); (3) resistivity of the damaging medium, and; (4) half-cell potential measurements. Methods (1) to (4) average over sample area (e.g, corrosion rate by LPR), or determine the concentrations or permeation rates averaged over large dimensions. These traditional methods have provided a valuable resource for predicting behavior and corrosion failure, but the “wired” approach limits the extension to buried interfaces and isolated damaging fluid exposure. Other approaches designed for industrial conditions are cited by Dean [18], and a new textbook is an excellent resource for a fundamental background on corrosion science [19]. To take advantage of wireless techniques to characterize the corrosion of “buried” metals, New Wireless Sensors should be:(1) Small so that they are not intrusive and do not alter local conditions in occluded regions;(2) Inexpensive so that multiple units can be embedded at distributed locations;(3) Tailored to enable unequivocal predictions of the metal corrosion process intechnological conditions, and; (4) Robust to ensure durability before the onset of corrosionPrevious wireless chemical (corrosion) sensor research involve passive sensors or threshold sensors. For example, a major type of passive RFID sensor (Class A) does not have a corrosion monitoring function. An example was reported by Andringa, et al [20](2005) with a design “window” for exposure of a portion of the sensor antennae to a damaging fluid. If the sensor fails to respond to interrogation, it is assumed to have “failed”. Similar sensors by Dickerson, et al [21](2006) and by Materer, et al [22](2009) have similar functions. However, these techniques can give a false positive, because the failure mechanism may be unrelated to corrosion. Other sensors measure threshold concentrations of damaging species such as H+, or Cl-, or other properties [23-24]. With integrated electronics, one can design the voltage readout function to exclude signals below the desired threshold. A passive RFID chip has been used to exclude measurements of the Cl- ion that were below a threshold concentration [25]. A third sensor type is activated when an embedded conductivity array becomes immersed in a condensed fluid. An “always-on” battery component is embedded with the conductivity array to provide power for the impedance measurement. These and other sensor types will be reviewed.An alternative active sensor design is to use a battery-assisted threshold chip for an “off/on” signal for wireless transmission. A battery is inactive until a damaging fluid arrives at the sensor location, and the battery-sensor turns “on” and powers a transmitter that signals the onset of damaging condition. The relative merit and advantages of the passive, threshold, and active sensors will be described.References available upon request – space in not sufficient

The nanotechnology of life-inspired systems.

For some decades now, nanotechnology has been touted as the 'next big thing' with potential impact comparable to the steam, electricity or Internet revolutions - but has it lived up to these expectations? While advances in top-down nanolithography, now reaching 10-nm resolution, have resulted in devices that are rapidly approaching mass production, attempts to produce nanoscale devices using bottom-up approaches have met with only limited success. We have been inundated with nanoparticles of almost any shape, material and composition, but their societal impact has been far from revolutionary, with growing concerns over their toxicity. Despite nebulous hopes that making hierarchical nanomaterials will lead to new, emergent properties, no breakthrough applications seem imminent. In this Perspective, we argue that the time is ripe to look beyond individual nano-objects and their static assemblies, and instead focus on systems comprising different types of 'nanoparts' interacting and/or communicating with one another to perform desired functions. Such systems are interesting for a variety of reasons: they can act autonomously without external electrical or optical connections, can be dynamic and reconfigurable, and can act as 'nanomachines' by directing the flow of mass, energy or information . In thinking how this systems nanoscience approach could be implemented to design useful - as opposed to toy-model - nanosystems, our choice of applications and our nanoengineering should be inspired by living matter.

Inkjet-Printed Multi-Bit Low-Voltage Fuse-Type Write-Once-Read-Many Memory Cell

Low-voltage fuse-type write-once-read-many memories were fabricated using a common material inkjet printer to form both the contact pads and the resistor tracks with the same silver ink and process settings. Based on the dependence of the fusing voltage on the length of the printed resistor track, a new cell structure was proposed to achieve multi-bit memories. The fabricated 2-b memory cell presents excellent long-term storage and operation stabilities, and 16-b memories were achieved using this cell structure with greatly saved contact pad numbers for easier external electrical connections than the conventional design. A system demonstration of using the memories was finally provided to prove the potential of this technology for practical use.

Bidirectional microfluidic pumping using an array of magnetic Janus microspheres rotating around magnetic disks.

We demonstrate a novel, flexible and programmable method to pump liquid through microchannels in lab-on-a-chip systems without the use of an external pump. The pumping principle is based on the rotation of ferromagnetic Janus microspheres around permalloy disks, driven by an external rotating magnetic field. By placing the disks close to the edge of the microchannel, a pumping rate of at least 0.3 nL min(-1) was measured using tracking microspheres. Geometric programming of the pumping direction is possible by positioning the magnetic disk close to the side wall. A second degree of freedom in the pumping direction is offered by the rotational direction of the external magnetic field. This method is especially suited for flow-controlled recirculation of chemical and biological species in microchannels - for example, medium recirculation in culture chambers - opening the way towards novel, portable, on-chip applications without the need for external fluidic or electrical connections.

Monolithic electrochemically promoted reactors: A step for the practical utilization of electrochemical promotion

A novel dismantlable monolithic-type electrochemically promoted catalytic reactor and “smart” sensor-catalytic reactor unit has been constructed and tested for hydrocarbon oxidation and NO reduction by C 2H 4 in the presence of O 2. In this novel reactor, thin (∼ 40 nm) porous catalyst films made of two different materials are sputter-deposited on opposing surfaces of thin (0.25 mm) parallel solid electrolyte plates supported in the grooves of a ceramic monolithic holder and serve as sensor or electropromoted catalyst elements. The catalyst dispersion was higher than 10%. A 22 flat plate reactor operated with apparent Faradaic efficiency up to 100, at near complete reactants conversion, at gas flow rates up to 30 l/min. The novel design has only two external electrical connections and thus significantly facilitates the practical utilization of electrochemical promotion of catalysis.

Coupled-resonator micromechanical filters with voltage tuneable bandpass characteristic in thick-film polysilicon technology

This paper reports on the design and characterization of 2.4 and 9.2 MHz fourth and sixth order passband microelectromechanical coupled-resonator filters implemented in a 15 μm thick-film epitaxial polysilicon technology. The work uses a novel approach in the building of coupled-resonator electromechanical filter structures using on-line controlled electrostatic coupling. Mechanical springs commonly used to couple micromechanical resonators were replaced by electrostatical links created by pairs of biased electrostatical transducers. To control the coupling strength, an original biasing scheme of electrostatical transducers is proposed. The idea is to maintain a fixed charge on the floating-potential middle electrode of the electrostatical coupler. This electrode does not need any external electrical connection, thus does not suffer from parasitic capacitances. The coupling factor is directly controlled by coupling transducer bias voltages, allowing the control of the filter pole frequencies. A voltage controlled bandpass filter at 9.2 MHz showed a bandwidth with a tuning range of 3.18–47.4 kHz.

Novel monolithic electrochemically promoted catalytic reactor for environmentally important reactions

A novel dismantlable monolithic-type electrochemically promoted catalytic reactor and “smart” sensor-catalytic reactor unit has been constructed and tested for hydrocarbon oxidation and NO reduction by C2H4 in presence of O2. In this novel reactor, thin (∼20–40nm) porous catalyst films made of two different materials are sputter-deposited on opposing surfaces of thin (0.25mm) parallel solid electrolyte plates supported in the grooves of a ceramic monolithic holder and serve as sensor or electropromoted catalyst elements. Using Rh/YSZ/Pt-type catalyst elements, the 22-plate reactor operated with apparent Faradaic efficiency exceeding 25 achieving near complete fuel and NO conversion at 300°C in presence of up to 1.1% O2 in the feed at gas flow rates exceeding 1.3l/min. The metal catalyst dispersion was of the order of at least 15%. The novel reactor design requires only two external electrical connections and permits easy practical utilization of the electrochemical promotion of catalysis.

Electrostatic inchworm microsystem with long range translation

The general design, fabrication, and development of an electrostatic translational microstage based on the inchworm principal of actuation is presented. The microstage is incorporated in a complete microsystem package that allows long range translation of the microstage through consecutive clamping to either an oscillating driver arm or stationary substrate. Actuation step size is user adjustable from 0.05 to 2 μm through the addition of a supplementary electrostatic actuator that controls the oscillation amplitude of the driver arm. Voltage to the microstage is delivered through coupled series capacitors allowing all external electrical connections to reside on the stationary substrate and allowing the microstage to translate free from the mechanical disturbances caused by direct electrical wiring. The inchworm microsystem is capable of arbitrarily large translation distances with nanometer resolution.

Single-side biasing of silicon drift detectors with homogeneous light-entrance window

In this work, we present a biasing scheme for silicon drift detectors (SDD's) with a homogeneous light-entrance window. The aim of the proposed solution is to provide a biasing of the single electrode of the detector on the light-entering side (back electrode) without any external electrical connection. The control of this electrode is performed by suitably biasing only the electrodes plated on the opposite side of the detector. In this mechanism, the leakage holes collected by the back electrode are used to create a reach-through current through the depleted bulk to the front side of the detector. This biasing scheme is of particular interest when the SDD has to be coupled to scintillators for /spl gamma/-ray spectroscopy and imaging applications. In this paper, the biasing scheme is presented and results obtained using the method with a cylindrical SDD are reported.

Fast silicon drift photodiodes free from bias connections on the light entering side

A new type of silicon drift photodiode intended to be coupled to large area scintillators is described. The diodes have a relatively large area (1 cm 2) and a short maximal drift time (300 ns). They operate without requiring any external electrical connection at the side of the photodiode coupled to the scintillating crystal. These new photodiodes have almost identical ring structures on both sides with individual rings being at linearly increasing potentials providing the required high electric drift field. A new feature of the presented photodiodes is a small modification of the electrode structure near the signal collecting anode. It allows a full depletion of the photodiode and the highest drift field. Advantages and drawbacks of this kind of photodiodes are described.

Interfacial Charge-Transfer Pathways: Evidence for Marcus-Type Inverted Electron Transfer in Metal Oxide Semiconductor/Inorganic Dye Systems

Under high driving force conditions, solution-phase chargetransfer processes are often characterized by Marcus-type inverted reactivity, i.e., a decrease in rate with an increase in thermodynamic driving force.1 In contrast, interfacial charge-transfer reactions tend to exhibit either Marcus normal region behavior or asymptotically constant rate behavior.2 The usual explanation for such behavior, at least at metal/solution interfaces, is the availability of a range of filled states below the Fermi level and a range of empty states above the Fermi level of the electrode, such that lower driving force reaction pathways are always available. If the lower driving force pathways are faster, then asymptotic rather than inverted kinetic behavior will be encountered. With semiconductor/solution interfaces, however, the existence of a finite band gap eliminates states immediately above the Fermi level (p-type semiconductors) or immediately below the Fermi level (n-type semiconductors) and opens up the possibility of inverted interfacial reactivity. Indeed, inverted behavior has often been invoked to explain the otherwise surprisingly slow back-electron-transfer reactivity typically encountered at inorganic-dye-sensitized metal oxide semiconductor/ solution interfaces.3 Nevertheless, in the few cases where driving force effects at the semiconductor/dye interface have been systematically investigated, either by manipulating band edge energetics or by manipulating molecular dye redox potentials, either Marcus normal region behavior or driving-force-independent kinetic behavior has been observed.2,4-7 We now report the direct observation of inverted interfacial electron-transfer reactivity at a molecular-dye-modified semiconductor/solution interface. The systems examined were classic ruthenium tris(polypyridine) complexes (homoleptic complexes), electrostatically bound to tin dioxide nanoparticles.8 Photoexcitation of the complexes leads to rapid electron injection into the semiconductor particle, followedsin the absence of an external electrical connections by back electron transfer, as shown in eqs 1 and 2.

A Multisectioned Porous Electrode for Synthesis of D‐Arabinose

A multisectioned flow‐through porous electrode, consisting of alternating conducting and insulating sections, was designed, built, and tested for the electrosynthesis of D‐arabinose in aqueous solution. The laboratory prototype, consisting of ten independent porous graphite slices each of 5 mm thickness, can be adapted by external electrical connection to allow both traditional and sectioned operations to be run in a single device. The experimental study in this work focuses on use of the multisectioned arrangement to improve current‐distribution uniformity in the porous‐electrode reactor. A model electrosynthesis system, consisting of oxidation of sodium gluconate to D‐arabinose in competition with the parallel reaction of oxygen evolution, has been chosen for investigation. Measurements in the sectioned electrode show that the performance, expressed in terms of current efficiency for gluconate oxidation, increases significantly with an increase in the number of sections. A comparison of predicted theoretical performance with experimental measurements on the ten‐section prototype has been used to extrapolate the performance of the sectioned electrode to configurations with larger numbers of sections. Extrapolation indicates that optimal performance in the 5 cm electrode can be achieved with fewer than 100 sections, a design that is feasible to construct with modern microfabrication technology. © 1999 The Electrochemical Society. All rights reserved.

Application of transient current measurements: evidence for galvanic corrosive wear of aluminum by a polyperfluoroether lubricant

Transient currents serve as a sensitive probe of electrical activity during a tribology experiment. Using this tool, we have found evidence for electrochemically-enhanced corrosion and galvanic corrosive wear of Al-6061 alloy in the presence of a perfluoropolyether (PFPE) lubricant. Fomblin Z-DOL. Galvanic current and potential measurements were carried out in three experimental configurations: (1) an Al stylus was translated across a Z-DOL-coated Al substrate in a typical wear geometry. (2) an Al electrode was brought down perpendicularly onto an identical, Z-DOL-coated Al electrode, and (3) in a simple electrolytic cell. All configurations yielded readily measurable currents with corresponding potential differences of ∼300 mV. Corrosion during long-term Z-DOL exposure in galvanic cells was confirmed by the detection of significant Al concentrations in the oil. Analysis of oil employed in non-galvanic cells (same geometry, but no external electrical connection) showed essentially background Al concentrations. Scanning force microscopy (SFM) of Al surfaces exposed to Z-DOL in galvanic cells actualy smoother than as-polished surfaces, due to an electropolishing effect. The consequences of galvanic corrosion regarding lubricant lifetime and wear in applications of PFPE lubricants, including magnetic disks, are discussed.

Three Color Detection in the Charge Integration Regime by ATCD for Large Area Applications

AbstractLarge area color image scanners are currently being widely investigated. The a-Si:H/a-SiC:H Adjustable Threshold Color Detector (ATCD) recently presented by the authors is suitable for greatly simplifying the structure of the arrays since ATCDs have just two external electrical connections. This makes possible to use the row-column addressing of pixels.In this work, the transient operation of ATCDs in the charge integration regime is discussed. Charge integration is operated by photocurrent discharging the three series connected capacitances which compose the device structure. The penetration depth of the incident radiation depends on the wavelength and determines which of the three capacitances is discharged. The applied bias voltage determines the polarization of the three junctions and the three capacitance actually sensed. Correct blue, green and red light detection is shown in the read-out transients and the read-out and saturation times are presented. Finally design rules of the device and read-out system are given in order to achieve a correct detection of the three colors.