bluuebunny/crossref_metadata_2025 huggingface dataset:
Macroscopic Modeling and Simulation for Polymer Electrolyte Membrane Fuel Cells
Authors: Yoneda Masakazu , Tago Yukari , Suzuki Koshiro , Takimoto Masato , Ejiri Eiji
Published: November 2006

A numerical simulation tool with macroscopic models of mass and heat transport, electrical conductance and electrochemical kinetics in PEM fuel cells was developed to predict the effect of operating, structural and material condition on a large- scale cell performance. As a result, the parameters of these macroscopic models can be adjusted to reproduce the measured I- V curves under 12 operating conditions for the different reactant concentration, relative humidity and reactant utilization. Using a set of the adjusted parameters, the effect of operating, structural and material conditions on the performance of a 300cm2 serpentine cell was investigated.
A Simulation of Two-Phase Flow inside Polymer Electrolyte Membrane Fuel Cells
Authors: Yoneda Masakazu , Suzuki Koshiro , Takimoto Masato
Published: November 2006

Two-phase flow of gas and water inside the gas diffusion layer and the flow field of the Polymer Electrolyte Membrane Fuel Cells is investigated by direct numerical simulation. The effect of the microscopic structure of the gas diffusion layer on the distribution of water and the transport properties of the gas is examined.
PEM Fuel Cell System Modeling with Liquid Fuel Processing and Hydrogen Membranes
Authors: Jackson Gregory S. , Shields Eric , Pearlman Joshua , Seyed-Reihani Seyed Abdolreza , Bhargav Atul , Hearn Patrick
Published: November 2006

A system-level simulation tool was developed to understand the challenging trade-offs in integrating PEM fuel cells with both reforming of liquid-fuels (modeled as C12H23) for H2 production and H2 purification with membrane reactors. The model performs iterative detailed thermochemical calculations for mass, species, and energy balances at a component level to assess component operating temperatures and parasitic loads due to compressors (for the cathode flow, autothermal reformer air flow, and anode recirculation flow), pumps (for liquid fuel and water flows for the reformer), and cooling fans (for the fuel cell radiator and the exhaust condenser for water recovery). The results indicate that with current PEM fuel cell polarization curves, thermal efficiencies > 30% can be achieved when parasitic loads are low and fuel cell voltages are high (> 0.75). Water balance can be sustained for the system studied when effective ambient temperatures are <= 40 {degree sign}C.
Evaporatively-Cooled PEM Fuel-Cell Stack and System
Authors: Perry Mike L. , Meyers Jeremy P. , Darling Robert M. , Evans Craig , Balliet Ryan
Published: November 2006

In this paper we describe a new design and mode of operation for a PEM fuel cell. A fuel cell can be configured to operate with humidification of the membrane-electrode assembly (MEA) over the entire face of the cell, which minimizes local variations in relative humidity that can lead to mechanical stress on the membrane. Normally, using this humidification approach requires a rather large volume of circulating water to keep the stack in water balance and provide cooling to the cell by sensibly heating the circulating water. This external water volume can be a liability when attempting to start up a fuel cell power plant from the frozen state. By designing a system which allows the cell to be cooled evaporatively, the system water volume can be reduced significantly, and moving mechanical parts in contact with liquid water can be eliminated. We show a simple system schematic and some example results to demonstrate the viability of this novel system.
Investigating the Role of a Microporous Layer on the Water Transport and Performance of a PEMFC
Authors: Pharoah Jon G. , Peppley Brant , Atiyeh Hasan , Halliop Ela , Karan Kunal , Phoenix Aaron
Published: November 2006

A test station was modified to collect water from the anode and cathode exhaust streams of a PEM fuel cell. Various combinations of cells were built and tested with (SGL10BA) and without microporous layers (SGL10BB) on the electrodes. Cells with a MPL at the cathode performed much better compared to cells with no MPL and the degradation rates were decreased. Water balance experiments were conducted with two combinations of inlet relative humidities (RH): 100% anode-60% cathode and 60% anode-100% cathode at current densities of 300, 500 and 700 mA/cm2. For the range of current densities studied, the net drag coefficient at 60{degree sign}C was -0.08-+0.08 mol H2O/mol H+ for RH 60% anode and 0.01-0.2 mol H2O/mol H+ for RH 100% anode. There was no significant change in the drag coefficient attributable to the presence of the MPL on the cathode. A MPL on the anode did affect the net water drag.
Preparation of Carbon Supported Ru-Se Based Catalysts and their Electrochemical Performance in DMFC Cathodes
Authors: Fiechter Sebastian , Bogdanoff Peter , Zehl Gerald , Dorbandt Iris , Schmithals Gerrit , Wippermann Klaus , Radnik Jörg , Richter B
Published: November 2006

Ruthenium catalysts were prepared employing aqueous solutions of ruthenium salts as precursors to obtain 2 nm sized metal particles homogeneously dispersed on a CO2-activated carbon support after annealing in hydrogen at 200 {degree sign}C. Selenium treatment was performed pouring the reduced product into a H2SeO3 or a SeCl4 solution prior to reduction in hydrogen at 300 {degree sign}C and 800 {degree sign}C. RuSex clusters have been formed which convert into a RuSexOy cluster after exposure to air. The presence of selenium in the cluster surface leads to a significant stabilisa-tion against oxidation of the metallic core and enables a highly selective catalytic activity towards the oxygen reduction reaction. Varying metal loading, PTFE and NAFION content in the cathode layer of a DMFC-MEA structure, best results were obtained using a metal loading of 1 mg/cm2 obtaining power densities of 20 mW/cm2 at a cell voltage of 0.4 V in a single cell.
Composite Polymer Electrolyte for Direct Ethanol Fuel Cell Application.
Authors: Di Blasi Alessandra , Baglio Vincenzo , Stassi Alessandro , D'Urso Claudia , Antonucci Vincenzo , Arico' Antonino S.
Published: November 2006

An electrochemical investigation has been carried out by using ethanol as alternative liquid fuel to methanol in a Direct Alcohol Fuel Cell (DAFC). Although methanol shows better performance with respect to ethanol, this latter represents a suitable fuel for DAFC; it is not toxic, it can be obtained from biomasses and it has a theoretical mass energy density larger than methanol. 85%Pt-Ru/C and 60%Pt/C in-house catalysts have been prepared for ethanol electro-oxidation and oxygen electro-reduction reactions, respectively, by the sulfite complex route. A composite membrane composed by Nafion ionomer and silica was fabricated in order to maintain the advantageous water retention properties of these materials at high temperatures (90-145{degree sign}C). The electrochemical behaviour of the composite membranes was also investigated in DEFCs at low temperatures (60-80{degree sign}C).
Formic Acid Tolerance on RuxSey during the Oxygen Reduction Reaction in Acid Medium
Authors: Arriaga Luis G. , Gochi Yadira , Alonso Nicolas
Published: November 2006

In the present work ORR results on RuxSey in presence of formic acid are reported and compared to Pt/C. Both materials were synthesized by the carbonyl chemical way. The advantages of the RuxSey for the ORR with respect to the Pt/C are discussed. The studies were made in half-cell arrangement at 25{degree sign}C and with different formic acid concentrations (0.01M, 0.1 M and 1M). The first results show performance loss of 0.10 V at a current density of 0.1 mA/cm2 for the RuxSey in 1 M of HCOOH. Using the half-cell data, the current-potential polarization and power density curves for a membrane-less system based on formic acid, using RuxSey as cathode, and Pd as anode were generated
Development of Electrocatalysts for the Solid Alkaline Membrane Fuel Cell (SAMFC)
Authors: Lamy Claude , Demarconnay Laurent , Coutanceau Christophe , Léger Jean-Michel
Published: November 2006

The preparation of platinum-based catalysts dispersed onto a carbon support (Vulcan XC-72) is presented. The water-in-oil microemulsion method was used to synthesize several electrocatalysts (Ag/C, Pt/C, PtPd/C, PtBi/C, PtPdBi/C) because it is more appropriate that the colloidal way derived from the Bönneman method. The electroactivity of anodic and cathodic catalysts towards the electrooxidation of EG and oxygen reduction, respectively, is investigated and their electrical performances in a SAMFC are evaluated at room temperature. An improvement of the cell performance from 18 mW cm-2 to 30 mW cm- 2 was obtained at 20{degree sign}C.
Low-Leakage Ultra-Scaled Junctions in MOS Devices; from Fundamentals to Improved Device Performance
Authors: Duffy Ray , Heringa Anco , Loo Josine , Augendre Emmanuel , Severi Simone , Curatola Gilberto
Published: November 2006

The aim of this work is to design ultra-scaled low-leakage junctions suitable for metal-oxide-semiconductor device scaling in bulk silicon. We begin with fundamental diode characterization analysis. Electrical behavior of fabricated diodes is then used to validate our device simulation modeling methodology, where established models are used to gain further insight and understanding in the junction leakage problem. Based on that effort, innovative junction scaling solutions are generated and realized in a silicon device experiment. Finally improved transistor performance is demonstrated.
Novel Methods For Ultrashallow Low Resistance Junction Formation
Authors: Jain Sameer H. , Griffin Peter , Plummer James
Published: November 2006

Source drain parasitic resistance is expected to become one of the major roadblocks to the continued improvements of device performance. According to the ITRS roadmap, the source drain parasitic resistance is expected to become as much as 26% of the intrinsic device resistance by the 45 nm technology node. This has driven the development of annealing tools where the silicon surface is heated and then cooled down on the time scale of milliseconds. While these tools provide improved activation, the boron activation here is limited by the solid solubility. It has been observed that the boron activation obtained after solid phase epitaxial regrowth increases with the temperature at which the regrowth is carried out. By carrying out the regrowth at a high temperature it is possible to obtain active concentrations as high as 6.5×1020/cm3 - well above the solubility limits of B in silicon. Due to the low thermal budget, the profiles undergo very little diffusion, resulting in extremely abrupt junctions that are limited only by the implanted profile.
Crystal Damage Removal by Spike and Flash Annealing
Authors: Lerch Wilfried , Paul Silke , Niess Juergen , McCoy Steve , Gelpey Jeff , Cristiano Fuccio , Duffy Ray , Boninelli Simona , Marcelot Olivier , Francesco Pier
Published: November 2006

The formation of extended defects resulting from the precipitation of the large amounts of interstitials and vacancies generated during the dopant and pre-amorphisation implantation is the major issue related to the formation of highly doped p+/n junctions. Interactions between defects and implanted dopants produce diffusion and activation anomalies that are among the major obstacles to the realisation of ultra- shallow junctions satisfying the ITRS requirements. The ideal thermal treatment should remove all the damage and get a high dopant activation with minimal diffusion. Modifying first the depth of the end-of-range damage by varying the pre- amorphisation implantation energy and the thermal budget by using second (spike) and millisecond (fRTP) annealing, the optimal values for implantation energy and thermal budget can be extracted for a complete defect annihilation. Transmission electron microscopy is used to determine the crystal quality.
Material-Inversion Solid-Phase Epitaxy of p+ Si for Elevated Junctions
Authors: Civale Y. , Nanver Lis K. , Schellevis H.
Published: November 2006

A solid-phase epitaxy (SPE) process that forms ultra-shallow abrupt aluminum p+-doped Si islands has been studied for deposition temperatures from 400 to 500 ºC. The growth process gives a very uniform composition of the p+ layer and an abrupt doping transition to the Si substrate. Low ohmic contacting and near-ideal diode characteristics are reliably obtained.
Low Temperature Silcore® Deposition of Undoped and Doped Silicon Films
Authors: Fischer Pamela R. , Van Aerde Steven , Oosterlaken Ed , Bozon Bart , Zagwijn Peter M. , Bauer Matthias , Yan Min , Verweij Wilco
Published: November 2006

The deposition and film properties for Silcore®-based silicon film deposition, both undoped and doped, are discussed for two different hardware configurations, a vertical furnace and a single wafer reactor. Silcore chemistry provides an alternative means of silicon film deposition as compared to traditional silane chemistry, with the key advantages being the lower deposition temperature regime achievable and smoother resulting silicon films.
State-of-the-Art Characterization for 65 nm CMOS Processes and Beyond
Authors: Hopstaken Marco , Juhel Marc , Gonchond Jean-Pierre , Kwakman Laurens , Wyon Christophe
Published: November 2006

Characterization of advanced CMOS devices and control of front- end of line (FEOL) processes require state-of-the-art analytical techniques and specific measurement protocols. Dynamic Secondary Ion Mass Spectrometry (D-SIMS) is well suited for in-depth quantitative analysis of both bulk- and dopant concentrations in GexSi1-x binary alloys. A similar D-SIMS protocol -in combination with Auger Electron Spectroscopy (AES) - allows monitoring nickel-silicide phase transitions upon silicidation of (doped) Ni Totally Silicided (TOSI) gates. Combination of Low-Energy Electron X-ray Emission Spectroscopy (LEXES) and high-precision DSIMS provides accurate control of dose, junction depth, and wafer uniformity for Ultra-Shallow Junctions (USJ) at high analytical throughput, opening the way to USJ metrology. Similar techniques (LEXES, SIMS) are employed to control wafer uniformity of deposited NiPt metal films as Source/Drain (S/D) contact metal, to monitor NixSi1-x phase transformations and Pt-redistribution upon silicidation, and to determine root causes of defectivity at the device level (micro- AES). The given examples demonstrate the importance of having available (novel) state-of-the-art characterization techniques - pushing the analytical limits in terms of resolution, sensitivity, and accuracy while simultaneously increasing throughput and reproducibility- to support process development, improve yield, and to speed up yield learning of advanced CMOS processes.
Laser Spike Annealing of Strained Si/ Strained Si0.3Ge0.7/ Relaxed Si0.7Ge0.3 Dual Channel High Mobility p-MOSFETs
Authors: Ni Chleirigh Cait , Wang Xiaoru , Rimple Gana , Wang Yun , Canonico Michael , Theodore David D. , Olubuyide Oluwamuyiwa , Hoyt Judy L.
Published: November 2006

Sub-melt temperature laser spike annealing is investigated as a low thermal budget solution for source/drain annealing in strained Si/ strained Si0.3Ge0.7/relaxed Si0.7Ge0.3 dual channel p-MOSFETs. A constant hole mobility enhancement factor of 4x is maintained relative to Si control MOSFETs, for laser annealing temperatures up to approximately 1000ºC. This temperature is significantly higher than possible with rapid thermal annealing, due to device degradation associated with Ge diffusion during rapid thermal annealing. Mobility is found to decrease dramatically in the heterostructure MOSFETs for laser annealing temperatures above ~ 1000ºC. SIMS analysis shows very little Ge diffusion, even for an 1100ºC laser anneal. Capacitance-voltage analysis and Raman spectroscopy suggest that there is some strain relaxation for the 1100ºC anneal. Transmission electron microscopy analysis indicates localized strain variation and defects on the order of 107 cm-2 for the heterostructure MOSFET subject to laser annealing at 1100ºC. The mobility degradation for LSA temperatures above ~ 1000ºC is consistent with a combination of strain relaxation and scattering from defects.
Current Challenges in Ge MOS Technology
Authors: Dimoulas Athanasios , Houssa M. , Ritenour A. , Fompeyrine J. , Tsai W. , Seo J.W. , Panayiotatos Y. , Tsipas P. , Brunco David P. , Caymax Matty R. , Locquet J.-P. , Dieker Ch.
Published: November 2006

Germanium high mobility metal oxide field effect transistors with high-k gates are considered to be good candidates for high performance applications. To develop a viable Ge MOS technology, we are facing a number of challenges. First, we need to engineer compliant Ge substrates in order to ensure volume production at low cost. Second, we must develop adequate Ge surface passivation methodology and identify appropriate high-k gate dielectrics to combine oxide scaling below 1 nm with good electrical quality of the interfaces. Finally, we need to master processing of Ge transistors to minimize the junction leakage and enhance channel mobility by at least a factor of 3 for both n and p-channel transistors.
Point-Defect Generation in Ni-, Pd-, and Pt-Germanided Schottky Barriers on N-Type Germanium Substrates
Authors: Simoen Eddy R. , Opsomer Karl , Claeys C. L. , Maex Karen , Detavernier Christophe , Van Meirhaeghe Roland , Forment Stefaan , Clauws Paul
Published: November 2006

In this paper, the creation of point defects in n-type germanium by Ni-, Pd or Pt-germanidation is investigated by means of Deep Level Transient Spectroscopy (DLTS). The germanidation is achieved by a Rapid Thermal Annealing (RTA) step between 300 and 500oC of a 30 nm sputtered metal layer. Contrasting behaviour is found between Ni, on the one hand, and Pd and Pt, on the other: in-diffusion of nickel is found starting from 400oC, while in the second case, vacancy-related deep levels have been observed at the lower RTA temperatures. Evidence will be provided that these defects are most likely formed during the sputtering of the heavy metal atoms, introducing radiation damage in the Ge substrate. Finally, the impact of these deep levels on the current-voltage (I-V) characteristics of the obtained metal-germanide Schottky barriers will be discussed.
Epitaxial III-V Nanowires on Silicon for Vertical Devices
Authors: Bakkers Erik , Borgstrom Magnus , van den Einden Wim , van Weert Maarten , Helman Ana , Verheijen Marcel
Published: November 2006

We show the epitaxial integration of III-V semiconductor nanowires with silicon technology. The wires are grown by the Vapor-Liquid-Solid (VLS) mechanism with laser ablation as well as metal organic vapor phase epitaxy. The VLS growth enables the fabrication of complex axial and radial heterostructures to optimize device performance. The hetero-epitaxial growth of the III-V nanowires on silicon was confirmed with X-ray diffraction pole figures and cross-sectional transmission electron microscopy. In addition, e-beam lithography was used to predefine the position of the nanowires. Finally, the synthesis of heterostructured nanowires is discussed
High-Performance Low Temperature Poly-Silicon Thin Film Transistors Fabricated by Excimer Laser Irradiation with Bottom-Gate Scheme
Authors: Tsai Chun-Chien , Chen Hsiu-Hsin , Lee Yao-Jen , Chen Hsiu-Hsin , Cheng Huang-Chung
Published: November 2006

In this work, high-performance low-temperature poly-Silicon bottom-gate TFTs with single grain boundary perpendicular to the current flow in the channel regions have been demonstrated. A lateral grain growth of 0.75 μm in length could be artificially grown via the super lateral growth phenomenon using excimer laser irradiation with the plateau structure. Consequently, bottom-gate TFTs made by this method exhibit higher field-effect-mobility, lower leakage current, steeper subthreshold slope, larger on/off current ratios and improved device uniformity owing to this location-manipulated lateral grains. In addition, it shows better reliability because of the smooth interface between gate dielectric and poly-Si channel films.
230 DPI High Resolution AMPLED Display on Flexible Metal Foils with Integrated Row Drivers
Authors: Troccoli Matias , Chuang Ta-Ko , Hamshidi Abbas , Kuo Po-Chin , Spirko Jeffery , Hatalis Miltiadis , Voutsas Apostolos T. , Afentakis Themis , Hartzell John
Published: November 2006

This paper presents a 230 dpi Active Matrix Polymer Light Emitting Diode (AMPLED) display on flexible stainless steel substrates fabricated with laser annealed poly-silicon TFT technology. The high resolution display is based on the standard 2 TFT pixel circuitry to form a full VGA array. Polysilicon TFT based shift registers for integrated row driving are also demonstrated. Display fabrication is compatible with standard polysilicon TFT CMOS processing temperatures and conditions. This paper discusses backplane fabrication, PLED deposition and display encapsulation; all performed in-house.
Sensitivity of Suspended-Gate Polysilicon TFTs to Charge Variation and Application to DNA Recognition
Authors: Mohammed-Brahim Tayeb , Bendriaa Farida , Le Bihan France , Salaun Anne-Claire , Bonnaud Olivier , Harnois Maxime
Published: November 2006

Suspended-Gate Polysilicon Thin Film Transistors, namely SGTFT, are fabricated using low temperature surface micro-machining process. When using sub-micronic gap, high field effect induces large shift of the transfer characteristics due to any charge variation inside the gap. The device was used in measurements of pH of different solutions with high sensitivity (~250 mV/pH), 4 times the theoretical Nernstian response and the usual value given by the known transducers. This high sensitivity, un-reached until now, is explained by the charge distribution induced by the high applied field. Application of the device is extended to DNA recognition with high and rapid answer. Whatever the application, SGTFT is sensitive to charge variation. Selectivity can be insured by the detection principle that is based on the couple DNA/complementary DNA in the case of DNA recognition
Uniform OLED-Pixels Using Microcrystalline Silicon TFTs for Active-Matrix Addressing
Authors: Mohammed-Brahim Tayeb , Gaillard Arc Hanmael , Rogel Regis , Crand Samuel , Prat Christophe , Leroy Philippe
Published: November 2006

Pixel circuits using undoped microcrystalline silicon as active layer have been investigated for the first time by LPCVD technique and implemented in organic light-emitting diodes (OLED) technology based active-matrix (AMOLED). AMOLED technology needs stable and uniform pixel circuits. In this way, key processes introduced here in OLED-pixel fabrication are low grain size to average the number of grain boundaries in the channel region of thin film transistor (TFT) and O2 plasma treatment to improve the gate SiO2/Si interface. P-type TFTs exhibit sub threshold voltage improvement of 20% and a hole mobility higher than 5 cm2/V.s. Furthermore, drive current and light intensity of OLED-pixels show uniformity better than 10%
Triple Stack Bonding for High Voltage Si Devices
Authors: Hobart K. D. , Kub Fritz J. , Phlips Bernard F. , Kurfess James D. , Neilson John
Published: November 2006

Direct wafer bonding of multiple wafers has been performed to demonstrate the utility of thick high resistivity float zone Si substrates for high voltage power devices and radiation detectors such as for X-ray and gamma-ray applications. Low-temperature triple-stack hydrophobic wafer bonding was used to preserve the properties of the float zone wafer sandwiched in the center of two fully processed device wafers. The device properties demonstrate that the high lifetime and high resistivity of the thick float zone wafer are preserved during processing.
New Generation of Structures Obtained by Direct Wafer Bonding of Processed Wafers
Authors: Aspar Bernard , Lagahe-Blanchard Chrystelle , Sousbie Nicolas , Margail Jacques , Moriceau H.
Published: November 2006

Direct wafer bonding is a generic technology enabling the fabrication of innovative structures. Adequate surface treatments allow bonding of virgin as well as partially or fully processed wafers, leading to new Anti-sticking BSOI, Patterned BSOI and Debondable BSOI with specific embedded functionalities. These engineered wafers answer to the evolution of requirements in microelectronics and microsystems.
Direct Wafer Bonding Enhanced by Ductile Layers Inserted Near the Interface
Authors: Olbrechts Benoit , Lejeune Bertrand , Bertholet Yannick , Pardoen Thomas , Raskin Jean-Pierre
Published: November 2006

This work demonstrates that the insertion of thin dissipative interlayers can substantially increase the resistance to fracture of interfaces obtained by wafer bonding. A multiscale numerical modelling strategy has been developed in order to quantify the protective effect resulting from the presence of a plastically deforming interlayer. The concept has been applied, for experimental demonstration, to a system known to be difficult to bond, i.e. PECVD SiO2/PECVD SiO2 interface. The introduction of a 1 micrometer thick aluminium interlayer next to the interface has lead, on average, to an increase by 67% of the overall interface fracture toughness. Proper combinations of interlayer thicknesses and mechanical properties can theoretically lead to improvement of the fracture energy by a factor of up to 10.
Enhance the Luminance Intensity of InGaN-GaN Light-Emitting Diode by Roughening both the p-GaN Surface and the Undoped-GaN Surface Using Wafer Bonding Methods
Authors: Wu Yewchung S. , Wei Chih Wei Chih
Published: November 2006

An InGaN-GaN light emitting diode (LED) with double roughened surfaces was fabricated by surface-roughening, wafer-bonding and laser lift-off technologies. It was found that the frontside luminance intensity of double roughened LED was 2.77 times higher than that of the conventional LED at an injection current of 20 mA. The backside luminance intensity was 2.37 times higher than that of the conventional LED. This is because the double roughened surfaces can provide photons multiple chances to escape from the LED surface, and redirect photons, which were originally emitted out of the escape cone, back into the escape cone.
Wafer Bonding Technologies in Industrial MEMS Processing - Potentials and Challenges
Authors: Knechtel Roy
Published: November 2006

This paper will give an overview of the use of wafer bonding technologies, in particular, semiconductor direct bonding, glass frit bonding and anodic bonding, in the manufacture of MEMS devices. The potential of these processes is illustrated, as well as the challenges of integrating the bonding process into industrial processing.
Forced Hydrolysis vs Self-Hydrolysis of Zinc Acetate in Ethanol and Iso-butanol
Authors: Gattorno Geonel R. , Oskam G.
Published: November 2006

In the present work we have explored the synthesis of ZnO nanoparticles in two different alcohols, using an alkali- alcohol (forced hydrolysis) or water-alcohol mixture (self- hydrolysis) as source of OH- for initiation of the condensation reactions. Characterization of the particle size was accomplished by means of UV-Visible spectrophotometry. Results shows that self-hydrolysis takes place through simultaneous nucleation, growth and agglomeration processes, which are faster in iso-butanol than in ethanol. The forced hydrolysis occurs with fast nucleation in both solvents, but in iso-butanol a precipitation process occurs in the later stages of coarsening.
High Quality Monodispersed Oxide Nanoparticles Prepared by the Liquid Phase Deposition Method in Aqueous Polymer Solution
Authors: Deki Shigehito , Nakata Akiyoshi , Mizuhata Minoru
Published: November 2006

Monodispersed TiO2 nanoparticles were synthesized by the LPD process using polymer aqueous solution of polyethyleneglycol (PEG) in order to control reactivity of metal-fluoro complex and size of deposited TiO2 particles. Monodispersed well- crystallized anatase particles are found after several minutes and easily separated from the reaction solution. The particle size of obtained samples ranged from ca. 3-5 nm with around 10% of standard deviation values. The synthesizing method presents a new route for preparing well-crystallized metal oxide nanopartcles with potential applications at an ambient condition.
Electrocatalytic Activity of Nano-Crystalline Ni-Co-Mo-Fe Alloys on the Oxygen Evolution Reaction (OER)
Authors: Domínguez Miguel A. , Plata Magdalena , Torres Aidé M. , Ramírez Claudia , Arce Elsa M.
Published: November 2006

Abstract The electrocatalytic behavior of nanocrystalline Co30Ni70, Co40Mo60, Ni40Mo60, Co15Ni30Mo55, Fe10Co35Ni55 and Co15Fe30Ni55 mol-% alloys on the oxygen evolution reaction [OER ] in a 30 wt-% KOH aqueous solution at 298, 323 and 343 K has been assessed in this work. Appreciable currents for oxygen evolution reactions were measured at Ni-Co-Mo-Fe electrodes produce by this technique. It was also found that iron increased the electrocatalytic activity for oxygen evolution reaction, but it was not as good as obtained on hydrogen evolution reaction [HER]. Tafel plots of preoxidized and prolonged cycled Co30Ni70, Co40Mo60, Ni40Mo60, Co15Ni30Mo55, Fe10Co35Ni55 and Co15Fe30Ni55 crystalline electrodes were very different, which might be related to changes in the surface enrichment of one or two of the alloy constituents. The electrocatalytic effects Mo seem to be more important on the OER at high temperatures than those showed previously for HER. Nickel and Molybdenum rich alloys showed particularly high activity towards the OER in comparison with their nanocrystalline counterparts.
Pr0.8Sr0.2Co1-xFexO3 Nanocrystalline Powders: Electrochemical Characterization for Solid Oxide Fuel Cell Cathodes
Authors: Magnone Edoardo E. , Traversa E. , Miyayama Masaru
Published: November 2006

Single-phase nanocrystalline powders in the Pr0.8Sr0.2Co1- xFexO3 series (x = 0.0, 0.2, 0.5, 0.8, and 1.0) were prepared using a single-step combustion synthesis at low temperatures, based on the auto-ignition reaction of a nitrate solution in the presence of citric acid. These powders were used to prepare symmetrical cells with Sm- doped ceria electrolyte, whose Pr0.8Sr0.2Co1-xFexO3/Ce0.8Sm0.2O2-x interfaces were studied using electrochemical impedance spectroscopy (EIS) measurements. In particular, the impedance of the Pr0.8Sr0.2Co1- xFexO3 electrodes was analyzed as a function of the overpotential, temperature, and oxygen partial pressure. The EIS plots were decomposed into at least two semicircles, which could be attributed to different elementary processes at high- and low-frequencies. The low frequency contributions strongly depended not only on temperature, but also on gas atmosphere and overpotential.
Chemical Sensors Based on Metal Oxide Nanostructures
Authors: Hunter G. , Xu Jennifer , Evans Laura , Vander Wal Randy , Berger Gordon , Liu C. C.
Published: November 2006

This paper is an overview of sensor development based on metal oxide nanostructures. While nanostructures such as nanorods show significant potential as enabling materials for chemical sensors, a number of significant technical challenges remain. The major issues addressed in this work revolve around the ability to make workable sensors. This paper discusses efforts to address three technical barriers related to the application of nanostructures into sensor systems: 1) Improving contact of the nanostructured materials with electrodes in a microsensor structure; 2) Controling nanostructure crystallinity to allow control of the detection mechanism; and 3) Widening the range of gases that can be detected by using different nanostructured materials. It is concluded that while this work demonstrates useful tools for further development, these are just the beginning steps towards realization of repeatable, controlled sensor systems using oxide based nanostructures.
Application of Three TiO2 Polymorphs in Photoelectrochemical Solar Cells
Authors: Vega Poot Alberto G. , Reyes Coronado David , Oskam G.
Published: November 2006

TiO2 nanoparticles have been synthesized in three phases in pure form, using amorphous TiO2 as a base material. Porous, nanostructured films were prepared using the doctor-blading method from a TiO2 suspension. After heating at 450 åC to remove the polymer, the films were sensitized with the dye N-719. Solar cells were prepared using a method of assembly designed to avoid evaporation of the solvent and the entrance of water and oxygen, and the efficiency of the solar cells was determined. The influence of the TiO2 structure on the solar cell performance is discussed.
Formation of HgCdTe by Electrochemical Atomic Layer Epitaxy (EC-ALE)
Authors: Venkatasamy Venkatram , Jayaraju Nagarajan
Published: November 2006

Formation of Hg(1-x)CdxTe (MCT), thin films by electrochemical atomic layer epitaxy (EC-ALE) is reported. EC-ALE is the electrochemical analog of atomic layer epitaxy (ALE) and atomic layer deposition (ALD), and thus involves the growth of films an atomic layer at a time, using surface limited reactions. Underpotential deposition (UPD) is a type of electrochemical surface limited reaction, used in the present study for the formation of good quality MCT deposits using EC- ALE. The MCT films were formed using an automated electrochemical flow cell deposition system, so that potentials and solutions could be exchanged as desired, without loss of potential control or exposure of the deposit to the ambient. Deposits were characterized using X-ray diffraction (XRD), electron probe microanalysis (EPMA) and reflection absorption Fourier transform Infrared spectroscopy (FTIR). The as-deposited films showed a strong (111) preferred growth orientation. The EPMA results indicated that the Cd rich film had an alloy composition of Hg0.5Cd0.5Te and the Hg rich film had a composition of Hg0.8Cd0.2Te. The bandgaps of the Hg0.5Cd0.5Te and Hg0.8Cd0.2Te deposits were measured to be 0.70 eV and 0.36 eV respectively.
Improvement in the Extraction Efficiency of AlGaInP and GaN Thin Film LEDs Via Surface Roughening
Authors: Kuo Hao-Chung , Lu T.C. , Lee Y.J. , Huang H. W. , Wang S.C. , Lin C. F.
Published: November 2006

In the first part of this paper, we present a LED structure adopting double diffused-surfaces on-top transmitted diffuse surface and another diffuse omnidirectional reflector surface on the bottom of LED chip. According to this design, guided light scattered by bottom diffuse omnidirectional reflectors can be again scattered toward to angles inside the escape cone by top diffuse transmittance surfaces. High light external efficiency (~ 40%) was achieved on this novel structure. This high efficiency could be attributed to the strong scattering efficiency of using double diffuse surfaces, further reducing trapping of light within LED chips. In the second part, we present n-side-up AlGaInP-based LEDs with a triangle-like surface morphology using the adhesive layer bonding technique, followed by wet etching to roughen the surface. The novel AlGaInP LED design could not only reduce internal reflection between rear mirror systems and the semiconductor/air interface, but also to effectively scatter light outside LED devices.
Properties of Rf Magnetron Sputter Deposited Cobalt Oxide Thin Films as Anode for Hydrogen Generation by Electrochemical Water Splitting
Authors: Ingler William B. , Attygalle Dinesh , Deng Xunming
Published: November 2006

The oxygen evolution reaction (OER) was investigated at room temperature in 33 wt% KOH solution on Co3O4 and Co3O4/NiO thin film electrodes. The electrodes were prepared by reactive radio frequency (rf) magnetron sputtering of Co and Ni in 20% O2/Ar atmosphere. Samples were made by optimization of various deposition parameters.
Optical Characterization of Zn1-xCdxO Alloys Grown by Molecular-Beam Epitaxy
Authors: Buyanova Irina A. , Wang Xingjun , Chen Weimin M. , Izadifard Morteza , Norton David , Pearton Steve J. , Osinsky Andrei V. , Dong Jianwei , Dabiran Amir M.
Published: November 2006

We have carried out comprehensive optical studies to evaluate structural and bandgap properties of Zn1-xCdxO alloys with x {less than or equal to} 0.17 grown by molecular beam epitaxy. High crystalline quality of the alloys was concluded from cathodoluminescence measurements. Based on absorption and reflectance measurements, the compositional dependence of the bandgap energy of ZnCdO, estimated without taking into account excitonic effects, was found to follow the trend Eg(x)=3.28- 2.23x+0.45x2. Degradation in the alloy quality due to possible phase separation was found to cause deviations from this trend, evident from a more rapid red shift of the absorption edge. Effects of Cd incorporation on the variation of the bandgap energies with temperature are also discussed.
Low-Temperature Heteroepitaxial Growth of 3C-SiC(111) on Si(110) Substrate Using Monomethylsilane
Authors: Konno Atsushi , Narita Yuzuru , Itoh Takashi , Yasui Kanji , Nakzawa Hideki , Endoh Tetsuo , Suemitsu Maki
Published: November 2006

Heteroepitaxial growth of 3C-SiC on Si(110) substrate has been successfully conducted at T=1000{degree sign}C by using monomethylsilane as a single source gas. X-ray diffraction (XRD) reveals that the growth orientation of the film is rotated and a 3C-SiC (111) film is formed on this Si(110) substrate. The film quality, as evaluated with the half width of the XRD rocking curve, shows betterment from that of 3C-SiC(111)/Si(111) film. The lattice constant anisotropy (a//-a⊥)/a// between the lateral and the growth directions also decreased by a factor of four from that of 3C-SiC(111)/Si(111), and the two lattice constants approach to that of bulk 3C-SiC. These results indicate significant reduction in the strain of the 3C-SiC film in this 3C-SiC(111)/Si(110) system. XRD-scan indicates presence of double domains with almost equal areas.
Fabrication and Electrical Characterization of Be-Doped Al0.42Ga0.58N MSMs
Authors: Hodge Michael D. , Stokes E. B. , Batoni Paolo
Published: November 2006

One of the greatest challenges facing GaN devices has been efficient p-type doping. Beryllium is a promising dopant for obtaining p-type conductivity in GaN. An investigation has been made into ionizing Be acceptors in AlGaN devices that has varying levels of Be implantation. The AlGaN samples had MSM structures placed on the doped surface in order to measure electrical characteristics. I-V characteristics were measured at room temperature without optical pumping. Future measurements with optical pumping through the use of a YAG IR laser are planned.
Modified Porphyrinic Sensor for Nitric Oxide Monitoring
Authors: Hrbac Jan , Gregor Cenek , Vostalova Jitka , Kralova Jana , Ciz Milan , Lojek Antonin
Published: November 2006

Carbon fiber, covered with nickel(II)poly-tetrakis(3-methoxy-4- hydroxyphenyl) porphyrin and Nafion® layers - porphyrinic sensor is one of the most widely used nitric oxide selective electrodes. It is also the earliest design of coated wire type nitric oxide sensor, suggested by Malinski et al. in the early 1990s. Electrocatalytical properties of poly-NiTMHPP are well documented in the literature but the poly-NiTMHPP layer has not been considered as an anti-interference barrier. In this contribution we describe that by careful adjustment of conditions used during the process of nickel porphyrin electropolymerization (the use of cyclic potential scanning regime for polymerization, optimum number of cycles, optimum porphyrin monomer concentration), and by modification of the Nafion coating process the sensors which are very selective for nitric oxide can be fabricated, without the need to compromise between selectivity and detection limit.
Automated Microarray Technology for Biomedical and Environmental Sensors
Authors: Aguilar Zoraida P. , Van Nguyen Chien , Sirisena Mali , Gertsch Jana , Arumugam Prabhu , Spencer Daryl , Wansapura Chamika , Aguilar Ysmael , Homesley Jerry
Published: November 2006

Studies toward the development of automated, rapid, sensitive, low-cost, and reliable biomedical and environmental assays using arrays of microcavities with three individually addressable electrodes is reported. Each microcavity in the array contains a bottom electrode called recessed microdisk electrode (or RMD), a middle layer electrode found along the wall called tubular nanoband electrode (or TNB), and a rim/top electrode. The microelectrode TNB was used to detect the signal from a microwell assay for as low as 100 pg of Plasmodium falciparum CSP gene over 5-min enzyme substrate incubation. A self-contained microelectrochemical assay for Cryptosporidium parvum was generated using the RMD for capture, the TNB as the detecting electrode, and the rim/top as the pseudoreference/auxiliary electrodes. The 4-μm distance of the capture surface to the TNB detecting electrode provided close proximity to the assay components which allowed for a rapid response where the first signal was recorded within 30 s of enzyme substrate incubation. The self-contained nature of the microcavity provided low cost assays with the use of reagents down to 200 nL. The self-contained microelectrochemical microarrays were compatible with automation that was demonstrated in the detection of 25 pg Bacillus anthracis anti-PA IgG in < 25 min total assay time.
Development of WO3-Based Thick-Film Hydrogen Sensors
Authors: Ahmad Aftab , Walsh Jennifer
Published: November 2006

ABSTRACT Hydrogen gas sensors based on semiconducting tungsten trioxide (WO3) were produced using a commercially attractive thick-film screen printing process. WO3 powders were doped with 1 mole % Pt or Pd and attrition-milled to produce precursor powders for sensor fabrication. The sensors were fired in air using various temperature/time profiles. SEM and XRD techniques were used to investigate the phase composition and microstructural properties. The influence of processing conditions, additives, sensor operating temperature and partial pressure of H2 gas on the response characteristics of the sensors was investigated. Sensors were also produced from un-doped material and tested under identical conditions to establish the baseline data. The data indicates that high-sensitivity H2 gas sensors can be produced through the manipulation of powder composition and processing conditions. The response characteristics of WO3- based sensors were found to be significantly influenced by the sensor operating temperature, the type of dopant used as well as the H2 gas concentration.
Influence of Interfaces on the Electrical Properties of Sintered Calcia-Stabilized Zirconia Solid-Electrolytes
Authors: Ahmad Aftab , Zhou Minghua
Published: November 2006

Precursor powders of 15 mol% calcia-stabilized zirconia solid electrolytes synthesized by a freeze-drying method, and a sol-gel method, were used to prepare oxygen sensors. Sensor elements were fabricated via uniaxial pressing of the calcined powders and subsequently sintered at 1650 {degree sign}C. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) techniques were used to analyze the microstructure, including the interfaces, grain boundary phases and impurity distribution, etc. The electrical response of the gas sensors to oxygen and the complex impedance in air were investigated at various operating temperatures. The correlations between grain microstructure and the impedance spectra characteristics of the sensors as well as oxygen sensing characteristics are discussed.
A Theoretical Framework for Prediction of Solid State Potentiometric Gas Sensor Behavior.
Authors: White Briggs M. , Macam Eric , Van Assche F. Martin , Traversa E. , Wachsman Eric D.
Published: November 2006

A 3 electrode, Luggin's Probe configuration was employed in making D. C. polarization and open-circuit potential (OCP) measurements on Platinum and La2CuO4 electrodes in atmospheres containing O2, NO, NO2, CO and CO2 at 500{degree sign}C. Each electrode potential, referenced to an isolated embedded reference electrode, changed when exposed to the aforementioned gases and the differences summed to equal the sensor signals previously seen when both electrodes were exposed to the same environment. Both the La2CuO4 and Pt electrode potentials went down when exposed to reducing gases (NO and CO) and went up when exposed to oxidizing gases (O2 and NO2). The Pt responses (DOCP) were larger than those for La2CuO4 for all gases. La2CuO4|YSZ|Pt sensors responded positively to NO and CO, negatively to NO2 and negligibly to O2. The D.C. polarization behavior for the Pt and La2CuO4 electrodes were contrasted and related to their individual gas responses (DOCPs).
Miniaturized Amperometric Solid Electrolyte Carbon Dioxide Sensors
Authors: Hunter G. , Xu Jennifer , Liu C. C. , Ward B. , Lukco D. , Artale M. , Lampard P. , Androjna D. , Hammond J.W.
Published: November 2006

A miniaturized electrochemical carbon dioxide (CO2) sensor using Na3Zr2Si2PO12 (NASICON) as a solid electrolyte has been fabricated and demonstrated. Microfabrication techniques were used for sensor fabrication to yield a sensing area around 1.0 mm x 1.1 mm. The NASICON solid electrolyte and the Na2CO3/BaCO3 (1:1.7 molar ratio) auxiliary electrolyte were deposited by sputtering in between and on top of the interdigitated finger- shaped platinum electrodes. This structure maximizes the length of the three-contact boundary (electrode, solid electrolyte, and auxiliary electrolyte), which is critical for gas sensing. The robust CO2 sensor operated up to 600ºC in an amperometric mode and attempts were made to optimize sensor operating parameters. Concentrations of CO2 between 0.02% and 4% were detected and the overall sensor performance was evaluated. Linear response of sensor current output to ln[CO2 concentration] ranging from 0.02% to 1% was achieved.
Diamond/Carbon Field Emission Based Structures for Sensors and MEMS
Authors: Davidson J. L. , Kang W. P. , Wong Y. M. , Subramamium K.
Published: November 2006

Chemical vapor deposited diamond/carbon micro- and nanostructures are excellent field emission cathodes for novel applications in sensors, MEMS, and NEMS because of their low electron affinity and excellent mechanical and chemical properties. However, practical micropatterning and fabrication of emitter structures are needed to fully exploit their potential use. This paper describes the use of microfabrication methods to achieve various forms of morphologically-engineered cathodes such as micro pyramidal tips with self-aligned gated membrane, nano-diamond lateral field emitters with built-in anode, and carbon-nanotube field emission arrays with self-aligned gate. We report the achievement of these micropatterned diamond/carbon field emission-based sensing platforms with excellent field emission characteristics. These field emitter-based microstructures are efficient sensing platforms from which novel sensors and MEMS can be derived.
Electrodeposited Micro-Actuators A Simple Tool for Impedance-Based Sensing
Authors: Enikov Eniko T.
Published: November 2006

This paper is focused on the design of metal (Ni) electro- thermal micro-actuators, fabricated via a single electro- plating step. Analytical and finite-element solutions of the electro-thermal and thermo-elastic problems are presented to aid in the design of the devices. A separate section is devoted to the problem of displacement determination using charge sensitive amplifiers for high-precision capacitance measurements. Finally, a possible future use of these actuators in impedance-based biosensors is outlined.