bluuebunny/crossref_metadata_2025 huggingface dataset:
Die-to-Die Adhesive Bonding for Evanescently-Coupled Photonic Devices
Authors: Stanković Stevan , Van Thourhout Dries , Roelkens Gunther , Jones Richard , Heck John , Sysak Matthew
Published: October 2010

Heterogeneous integration of III-V semiconductor materials on the SOI (silicon-on-insulator) platform is a promising method for fabrication of active photonic devices. It requires a reliable and robust bonding procedure that also enables an effective optical coupling between III-V layers and SOI waveguides. Molecular bonding is usually used for this purpose, but due to its strict requirements for contamination-free and smooth bonding surfaces, it might not be sufficiently robust for industrial-scale fabrication. As an alternative technique, in this paper we present an adhesive bonding procedure based on the use of DVS-BCB. We developed a die-to-die adhesive bonding procedure, resulting in less than 100nm-thick bonding layers thereby enabling evanescent optical coupling between III-V layers and silicon waveguides. The process shows very good robustness and bonding strength (brake-down shear stress of 2MPa). In perspective, we plan to scale-up the process to a multiple die-to-wafer bonding procedure which would be suitable for industrial-scale fabrication.
Properties of Interfacial Dislocations in Hydrophobic Bonded Si-Wafers
Authors: Reiche Manfred , Kittler Martin , Haehnel Angelika , Arguirov T. , Mchedlidze T.
Published: October 2010

The realization of defined dislocation networks by hydrophobic wafer bonding allows the characterization of electrical and optical properties of dislocations. The present paper investigates the electrical properties in samples containing only a few (up to 6) dislocations. By taking results of other analysis into account the electronic properties of individual dislocations can be described. The dislocation-induced luminescence between 1.3 µm and 1.5 µm was also analyzed using different types of light-emitting diodes (LED). It was shown that the emission depends on the structure of the dislocation network.
Defect Formation at Hydrophilic Silicon Bonding Interfaces
Authors: Rieutord François , Vincent Sebastien , Penot Jean-Daniel , Moriceau Hubert , Radu Ionut
Published: October 2010

The energetic and kinetic processes of bonding interface defect formation, growth and dissolution are studied for the standard silicon hydrophilic bonding case. Defects are shown to occur when the hydrogen pressure exceeds the interface strength, forming gas bubbles. The further growth of these defects can be modeled using standard diffusion provided adequate boundary conditions are used. Size dependence of defect dissolution at higher temperature can be modeled using non reversible crack formation energies.
The Characteristics of Interface Microstructures in Germanium/SiO2 Low Temperature Wafer Bonding
Authors: Zhang Xuanxiong , Ye Tianchun , Zhuang Songlin , Jiao Jiwei
Published: October 2010

Ge/SiO2 direct wafer bonding by O2-plasma pretreatment was investigated. The bonding interfaces of Ge/SiO2 low temperature direct wafer bonding were characterized by transmission electron microscopy. The perfectly atomic level Ge/SiO2 bonding was achieved after a 1500C annealing for 60 hours. The excessive O2-plasma exposure resulted in micro-crack formation close to the bonding interface in Ge. A model involved micro-crack formed in Ge was proposed. Our experiments, for the first time, demonstrated that a perfectly seamless bonding of Ge/SiO2 by O2-plasma pretreatment depends not only on optimal O2-plasma pretreatment time but also on the manner of the raised annealing temperature to enhance the bonding strength. A slowly ramping rate heating is crucial to accomplish perfectly seamless Ge/SiO2 wafer bonding apart from an optimal O2-plasma exposure time chosen.
Efficiency of H2O Diffusion Barriers at Si-Si Direct Bonding Interfaces
Authors: Moriceau Hubert , Rieutord François , Libralesso Laure , Ventosa Caroline , Fournel Frank , Morales Christophe , McCormick Tina , Chevolleau Thierry , Radu Ionut
Published: October 2010

Direct silicon wafer bonding is an attractive way to build up stacked structures. For applications, defect free bonding is required whatever the post bonding processes, which can include thermal treatment. Direct bonding processes are usually applied with hydrophilic surfaces. Thus water trapped at bonding interfaces can induce low temperature oxidation, which is a source of gas and bonding defects. The aim of this paper is to compare the efficiency of various H2O diffusion barriers, which can be elaborated onto silicon wafers before bonding. Behaviors of thin thermal silicon oxide, thermal silicon nitride and plasma induced silicon oxynitride capping layers have been evaluated and compared to a chemical oxide layer. The efficient role of thermal oxide or oxynitride layer as a H2O diffusion barrier has been pointed out.
Room-Temperature Bonding Using Fluorine Containing Plasma Activation and Its Bonding Mechanism
Authors: Wang Chenxi , Suga Tadatomo
Published: October 2010

Room-temperature Si/Si wafer direct bonding has been achieved successfully without wet chemistry treatment as well as no requiring annealing. Very strong bonding strength of Si/Si pairs, close to the bulk-fracture strength of silicon, is demonstrated at room temperature thanks to adding small amount of carbon tetrafluoride (CF4) into oxygen plasma treatment. Moreover, we focus on several crucial issues, such as effects of plasma treatment parameters on bonding strength, characterizations of bonding surface and interface. For this fluorine containing plasma activated bonding, fewer water molecules at bonding interface may prone to produce many covalent bonds via polymerization reaction and result in strong bonding at room temperature.
Innovative Megasonic Cleaning Technology Evaluated Through Direct Wafer Bonding
Authors: Fournel Frank , Bally Laurent , Dussault Don , Dragoi Viorel
Published: October 2010

Different microelectronic processes require very clean surfaces in terms of particulate contamination. Among them, direct wafer bonding has very aggressive requirement in terms of particulate cleanliness. Current work describes development, testing and verification of a single wafer megasonic cleaning method utilizing a transducer design that meets extreme particle neutrality, particle removal efficiency and repeatability requirements of production scale wafer bonding and other very low particle applications. Wafer bonding will also be used as a characterization technique.
The Study of the Bonding Energy on Silicon-to-Glass Wafer Bonding
Authors: Chuang Ta-Ko , Usenko Alex , Cites Jeffery
Published: October 2010

Corning's proprietary Silicon-on-Glass (SiOG) technology comprises two major processes - the wafer bonding and the layer transfer. Both processes govern the quality of the transferred film. A strong bond between the silicon and the glass substrates is desirable to facilitate the layer transfer process. The bonding energy between two substrates is a crucial measure to gauge the integrity of the wafer bonding and subsequently influences the final film-transfer properties. This work focuses on the characterization of the bonding energy as a function of temperature and attempts to understand the physical/chemical interaction occurring therein. Silicon wafers bonded to various glasses have been characterized. The correlation between the bond energy and the glass attributes, such as, Young's Modulus, strain point, coefficient of thermal expansion, surface roughness, constituents, are discussed.
Effect of Pattern Geometry on the Fracture Behavior of Direct Bonded Silicon Wafers
Authors: Kim-Lee Hyun-Joon , Turner Kevin T.
Published: October 2010

The effect of shallow and deep etched interface patterns on the effective adhesion of silicon-silicon direct bonds is examined. Specifically, fracture loads of double cantilever beam specimens with structured interfaces, with dimensions in micrometer regime, are measured. The results show that the interface fracture load increases as the structures, which are simple pillars, become taller and narrower. These experimental results are in good agreement with finite element modeling results. The fracture surfaces were inspected after testing, and the surfaces generally had very little debris from the bonded pillars. The results of this study may help to aid in the design of temporary bonding processes that use patterned interfaces to tune the failure behavior.
Development of Nonuniform Residual Stresses during Anodic Bonding
Authors: Horn Gavin P. , Gerbach Ronny , Lin Tung-Wei , Bernach Michael , Brand Sebastian , Johnson Harley T.
Published: October 2010

Nonuniform residual stresses may develop during anodic bonding due to variations in wafer curvature prior to bonding or due to nanotopography interactions between the bonding surfaces. In this work, we discuss the significance of nonuniform residual stress in anodically bonded wafer pairs and present a method for measuring local stress variations even in cases when the bonded wafers are apparently defect free based on conventional inspection tools. These residual stresses can vary significantly between two different wafers processed identically, depending on the local interactions, but they are present in all standard bonding methodologies. In some instances, these local residual stresses can significantly alter the resulting wafer curvature in apparently defect free substrates. Currently, anodically bonded devices or substrate wafers are considered "defect free" if no large debonds are found after bonding; however the residual stress state of the wafers cannot be determined using the same conventional techniques.
Anisothermal Anodic Bonding: A Method to Control Global Curvature and Residual Stress
Authors: Yadav Manish , Lin Tung-Wei , Johnson Harley T. , Horn Gavin P.
Published: October 2010

The manipulation and characterization of residual stress and wafer curvature in anodically bonded structures is useful in improving the reliability of devices built on silicon on glass substrates. Conventional anodic bonding procedures lead to uncontrolled curvature of the bonded substrates as a result of locked-in residual stresses due to thermal expansion mismatch between silicon and Pyrex. A thermomechanical finite element model is used here to elucidate the effect of thermal variations in wafer temperature during anodic bonding. The results inform the development of an anisothermal recipe to control the resulting residual stresses and post bond wafer curvature and to understand the effects of process control on residual curvature. The model suggests that wafer curvature in anodically bonded substrates can be nearly eliminated by reducing the silicon bonding temperature slightly relative to the Pyrex temperature. A simple quantitative model to predict this effect shows promising agreement with experiments.
Characterization of Hysteresis of Surface Energy in Room-Temperature Direct Bonding Processes
Authors: Grierson David , Turner Kevin T.
Published: October 2010

Room temperature direct wafer bonding is driven by surface forces and the formation of hydrogen bonds that provides a driving force to pull the wafers being bonded into intimate contact. The magnitude of these forces is often represented as a work of adhesion and is critical as it determines the level of non-flatness and patterning that may be tolerated in bonding. Traditionally, it has been assumed that the work of adhesion that drives the formation of the bond is equal to the work of separation that is measured through fracture tests, such as the familiar razor-blade test. In the present work, we use a novel test structure to measure the work of separation and work of adhesion of room temperature hydrophilic Si-Si bonds as function of relative humidity (~15 - 50% RH). The results show that across a range of values of RH the work of adhesion is significantly lower than the work of separation.
(Invited) The Legacy of Ulrich Gösele in the Science and Technology of Wafer Bonding and Smart Cut: In Memoriam Ulrich Gösele (1949 - 2009)
Authors: Reiche Manfred
Published: October 2010

It is generally known that Ulrich Gösele has made numerous important contributions in different distinguished areas in materials science: diffusion and defects in semiconductors, semiconductor nanoparticles and nanowires, silicon photonics and photonic crystals, self-organized nanoscale structures, and semiconductor wafer bonding. The paper will honor his contribution to the development of wafer bonding techniques and the understanding of the physical and chemical processes at the interfaces of bonded wafers.
(Invited) Ion-Cut from Smart to Smarter: Ulrich Gösele's Impact on Science and Technology of Ultrathin Layer Transfer
Authors: Moutanabbir Oussama
Published: October 2010

Ulrich Gösele made numerous contributions to the science and technology of semiconductor low dimensional systems, heterostructures and nanoscale structures. This paper will be based upon the personal experience of the author who worked directly with Ulrich Gösele on several fundamental and engineering subjects. In particular, the impact of Ulrich Gösele on the basic understanding and applications of the ion-cut process will be addressed.
Biosensors for the Detection of DNA Damage by Toxicants
Authors: Prance Amanda , Coopersmith Kaitlin , Stobiecka Magdalena , Hepel Maria
Published: October 2010

Novel DNA biosensors have been designed for testing DNA damage by toxicants. In this work, we describe the development of simple accelerated tests for DNA alterations by toxicants. To facilitate rapid testing, higher concentrations of reactants were investigated than those normally found in environmental and field samples. The sensors are based on electrochemical transduction with an intercalation redox probe. The damage and conformation changes of the immobilized DNA affect the penetration of the probe molecules and the redox current profiles. These robust sensors provide single base-pair mismatch sensitivity. In this work, the Methylene Blue and Nile Blue A redox probes were evaluated for testing DNA damage caused by an herbicide atrazine. Higher sensitivity was obtained using the Nile Blue (NB) dye as the active probe. Owing to the high sensitivity of the intercalator-probe uptake to the conformational alterations of DNA double-helix, the effects of DNA incubation in atrazine solutions could be assessed. We have found that the incubation of dsDNA with atrazine results in the increased activity of NB and an increased uptake of NB by the altered dsDNA. On the basis of this and other findings, the mechanism of atrazine interactions with DNA double-helix has been elucidated.
Nanoporous Sensors
Authors: Smirnov Sergei , Wang Xian
Published: October 2010

Organic modification of the surface of nanoporous alumina membranes allows construction of chemical and biochemical sensors that employ detection using simple AC conductance. In this article we demonstrate two applications of such sensors: a) DNA bisosensor based on the surface charge mechanism with morpholino (neutral DNA analog) as DNA ligand and b) humidity sensor with various surface modifications.
Advantage of Ultra Thin Overoxidized Polypyrrole Membrane in the Design of Amperometric Biosensor
Authors: Debiemme-Chouvy Catherine , Navarro Gwendoline
Published: October 2010

Recently, it has been shown that pyrrole electrooxidation in the presence of only weak-acidic anions allows one to locally, rapidly and in single step form on the electrode a pinhole-free ultra thin layer of overoxidized polypyrrole (OPPy). In this paper, it is shown that if this electrosynthesis is performed in the presence of glucose oxidase, the enzyme is entrapped into the OPPy membrane which covers the Pt electrode. Therefore, a glucose biosensor is obtained. When this sensor is in the presence of glucose, H2O2 is generated and leads to an anodic current at the electrode which is polarized at 0.65V/SCE. The amperometric responses of such a biosensor are presented in this paper.
Encapsulation of Enzymes inside Peptide Nanotubes for Hydrogen Peroxide Detection
Authors: Park Byung-Wook , Yoon Do-Young , Kim Dong-Shik
Published: October 2010

Biosensor matrixes have been developed using hydrogen peroxidase (HRP) as a model enzyme and peptide nanotube (PNT). The enzymes are encapsulated inside self-assembled PNT. The catalytic activity and the stability of the encapsulated HRP have been investigated. The electrochemical property of the PNT was characterized using cyclic voltammetry (CV) and compared with free enzymes. The formation of PNT was conducted by NH2-Phe-Phe-COOH dipeptides as building blocks. Scanning electron microscope (SEM) and atomic force microscope (AFM) were used to confirm the hollow nanostructure of the PNT. The encapsulation of HRP inside PNT was proved using scanning transmission electron microscope (STEM) and UV-Vis spectrophotometer. The result showed that the enzyme sensing matrix system incorporated with PNT provided an attractive advantage for a new type of electrochemical biosensors.
Fabrication of High Sensitivity pH-Meters by Nanoporous Silicon Structures
Authors: Shahmohammadi Mehran , Zehfroosh Nina , Mohajerzadeh Shams
Published: October 2010

Nano-porous structures were utilized as the sensitive surface of ISFET devices to improve their response to hydrogen concentration. The proposed sensor presents an ultra-high sensitivity pH-meter to detect H+ or OH- ions. This pH-meter is a field effect transistor with a non-symmetric gate capacitance. The area of the exposed surface is numerously larger than that of the channel area. Using this method, the effective gate capacitance increases significantly. Because of 3-dimentional geometry of the nano-porous poly-silicon region, the amount of the adsorbed charges increases and consequently the sensor response is dramatically higher.
Metabolic Assay System for Micropatterned Contractile Myotubes
Authors: Nagamine Kuniaki , Ido Yuichiro , Sekine Soichiro , Miyake Takeo , Kanzaki Makoto , Nishizawa Matsuhiko
Published: October 2010

Contractile C2C12 myotube line patterns embedded in a fibrin gel have been developed to afford a physiologically relevant and stable bioassay system. We found that the myotubes supported by an elastic fibrin gel maintained their line patterns and contractile activities for a longer period of time (one week) than myotubes adhered on a conventional culture dish. Now, we are investigating contraction-mediated translocation of the GLUT4 glucose transporter protein in myotubes using this system.
Electronically Directed Integration of Whole-Cell Biosensors on Bio-Chips
Authors: Ben-Yoav Hadar , Freeman Amihay , Sternheim Marek , Fishelson Nick , Rubin Adi , Biran Alva , Pedahzur Rami , Belkin Shimshon , Shacham-Diamand Yosi
Published: October 2010

This paper presents a whole-cell bio-chip system where viable, functioning cells are deposited onto solid surfaces that are a part of a micro-machined system. The development of such novel hybrid functional sensors depends on the cell deposition methods; in this work new approach integrating live bacterial cells on a bio-chip using electrophoretic deposition is presented. The bio-material deposition technique was characterized under various driving potential and chamber configurations. The deposited bio-mass included genetically engineered bacterial cells generating electrochemically active byproduct upon exposure to toxic materials in the aqueous solution. In this paper we present the deposition apparatus and methods, as well as the characterization results, e.g. signal vs. time and induction factor, of such chips and discussing the highlight and problems of the new deposition method.
Real-Time Biosensor Platform: Fully Integrated Device for Impedimetric Assays
Authors: Ghindilis Andrey L. , Schwarzkopf Kevin , Messing Dean , Sezan Ibrahim , Schuele Paul , Zhan Changqing , Smith Maria , Simon Holly , Evans David
Published: October 2010

An impedimetric biosensor platform for bio-affinity assays was developed based on real-time, label-free electrochemical detection performed via direct interface to electronic digital data processing. The sensor array consists of 15 gold microelectrode pairs enclosed in three reaction chambers and bio-functionalized with specific DNA probes. The impedance change caused by specific target analyte binding to the functionalized electrode surface is recorded in real time. The detector is capable of continuous and simultaneous stimulation and recording of all array electrodes. A corresponding mathematical algorithm, and a software package for data analysis were developed and used to quantify both the rate of target to probe binding, and target to probe affinity. The biosensor was capable of distinguishing between closely-related bacterial strains. This fully-integrated sensor array platform can be used for detection of a wide range of analytes of practical significance, and has potential for further integration with amplification (i.e. PCR) and sample preparation modules.
Nanomaterials in Medicine
Authors: Aguilar Zoraida P. , Aguilar Ysmael , Xu Hengyi , Jones Ben , Dixon John , Xu Hong , Wang Y. A.
Published: October 2010

Nanomaterials are currently being developed for various biomedical applications. Engineered nanomaterials such as quantum dots, metal and semiconductor nanoparticles, and magnetic nanoparticles are among the new materials being studied for medical applications. Nanomaterials have unique properties that include diameters from 3-50 nm, high quantum yields, resistance against photobleaching, high magnetic and electric properties, and simultaneous excitation of multiple fluorescent colors. Quantum dots have unique emission spectra even with ordinary source of light. Magnetic nanoparticles are unique because of their highly magnetic nature. Magnetic nanoparticles are used in magnetic resonance imaging and targeted drug delivery while quantum dots are increasingly being used for biomedical imaging. We report the results of our studies on the applications of nanomaterials in medicine. These include cell imaging, tissue imaging, protein detection, drug delivery, and cell targeting. Preliminary studies indicated promising applications of nanomaterials in molecular imaging and in vitro diagnostics.
Detecting Insect Infestation Using a Carbon/Polymer Composite Based Sensor Array
Authors: Weerakoon Kanchana A. , Chin Bryan
Published: October 2010

A carbon/polymer composite sensor array was designed, fabricated and tested to detect volatile organic compounds secreted by plants when attacked by insects. The sensor array is inexpensive and can be used for early onsite detection of insect infestation. The array is made of chemical resistor sensors which consists of micro-electronically fabricated interdigitated electrodes, coated with carbon/polymer composite thin films that was deposited by drop casting. The sensor array was exposed and found to sensitive to a variety of chemicals including γ-terpinene α-pinene, p-cymene, farnesene, limonene and cis-hexenyl acetate. The sensor array was also able to distinguish between each of the chemicals by creating a unique "finger print" pattern with the sensor responses.
Detection of Salmonella Typhimurium on Fresh Food Produce Using Phage-Based Magnetoelastic Biosensors
Authors: Li Suiqiong , Horikawa Shin , Shen Wen , Chin Bryan
Published: October 2010

Salmonella Typhimurium on fresh tomato surface using phage-based magnetoelastic (ME) biosensors. The ME biosensors are composed of a ME resonator platform that is coated with filamentous E2 phage (genetically engineered to bind with Salmonella). Actuated and detected through magnetic field, the ME biosensors are wireless sensors. In this study, tomato surfaces were spiked with a known number of Salmonella cells and then allowed to dry in air. The detection was conducted by directly placing ME biosensors on the spiked surface. Measurements of the resonance frequencies of both control and measurement ME biosensors were made prior to the placement and after 30 minutes of the placement. Shifts in the resonance frequency of the measurement biosensors were observed while control sensors showed negligible change. The specific binding of Salmonella to the biosensors was verified by Scanning Electron Microscopy (SEM). The results indicate that this methodology may provide real-time pathogen detection without traditional sampling process.
Statistical Investigation of a Novel Conditioning Method for Reliable Detection of Exhaust Gas Components
Authors: Sekhar Praveen Kumar , Brosha Eric , Mukundan Rangachary , Farber Boris , Garzón Fernando H.
Published: October 2010

The article reports on the statistical analysis of a new conditioning technique referred to as the pulsed discharge technique (PDT) with a view to understand the effect of PDT variables on potentiometric sensor response.
Selectivity Improvements and Response Time Scale of Porous Silicon Conductometric Gas Sensors
Authors: Ozdemir Serdar , Gole James L.
Published: October 2010

Nanopore covered microporous silicon conductometric gas sensors have been fabricated using electrochemical etching in an HF and acetonitrile solution and standard cleanroom microfabrication techniques. Sensing of NH3, NOx, PH3, and SO2 at or below the ppm level has been accomplished. A porous silicon (PS) surface has been modified using selective depositions formed from electroless tin, gold, nickel, and copper solutions to increase the response to several gases including PH3. The diffusion of the PH3 analyte has been investigated in the nanopore and micropore regimes by numerical analysis. By comparing the response time of the hybrid porous sensor surface with numerical diffusion calculations based on a realistic model of the pores, it is demonstrated that Knudsen diffusion time scales dominate the sensor response.
Sm0.95Ce0.05Fe1-xCrxO3-δ Perovskite Materials for Gas Sensing
Authors: Bukhari Syed M. , Giorgi Javier
Published: October 2010

Reducing-gas sensors based on Sm0.95Ce0.05Fe1-xCrxO3-δ (x=0-0.05) perovskites were prepared in the form of pellets. The sensor's surface is enriched with Cr due to surface segregation, and the Sm surface concentration varies along the series. The introduction of Cr in the perovskite lattice produces a rearrangement of charge within the perovskite structure, as indicated by changes in concentration of the different Fe species. The concentration of lattice and surface-adsorbed oxygen as a function of Cr concentration were found to be correlated with different Fe species. The electrical conductivity responses toward H2, CO and CH4 (1-5%v/v) were measured in air at different temperatures. All sensors showed good sensitivity towards the target gases at 200oC and 300oC but only x=0.01 was able to detect H2, CO and CH4 at 25oC. Response and recovery time are dependent on surface chemical composition and surface morphology.
Detection of Nitrogen Dioxide Gas in Nitrogen Atmospheres via Passive Monitoring of Iron (II) Phthalocyanine Thin Films
Authors: Shu John H. , Wikle Howard , Chin Bryan
Published: October 2010

Nitrogen dioxide (NO2) is a highly toxic oxidizing gas generally produced as a byproduct of combustion processes and also commonly stored in high concentrations as dinitrogen tetroxide (N2O4) for military and industrial use. A passive, unpowered sensor for the detection of NO2 gas was fabricated using Iron Phthalocyanine (FePc), an organometallic molecular crystal. FePc acts as an electron donor in the presence of Nitrogen Dioxide gas, forming a charge carrier complex, thus when FePc is exposed to NO2, the resulting decrease in resistivity can be monitored to determine ambient NO2 concentrations. Sensors were fabricated via physical vapor deposition of FePc powder onto gold inter-digitated electrodes patterned on oxidized silicon substrates. Gas exposure tests were conducted with sensor resistance monitored in real time. By observing normalized sensor resistance over time, NO2 concentrations in the range of 0.5 to 2 ppm under a N2 atmosphere were consistently detectable.
Self-Contained Microelectrochemical Assay with Enhanced Capture Surface for Sensitive Detection of Proteins
Authors: Wansapura Chamika M.
Published: October 2010

Detection of proteins at very low concentrations is of a major interest in biological, medical, and veterinary applications. Vegrandis has been developing self-contained microelectrode array sensors for the detection of low concentration of proteins. In order to improve the detection limits we have been exploring various compounds that enhance the capture surface of the biosensor. The preliminary results for three types of self-assembling monolayer (SAM) compounds used to modify Vegrandis' microarray sensor chips are reported. These compounds comprised of monothiols with biotin or hydroxyl terminated polyethyleneglycol chains or dithiolated scaffold attached to a central trisubstituted aromatic ring with a carboxylic acid terminated polyethyleneglycol chain. Results for the three SAM systems were compared using a simple mouse IgG model assay. The application of sensor chip towards the development of anti-mortem detection of prion proteins is also discussed.
Rigidity Percolation in Plasma Enhanced Chemical Vapor Deposited a-SiC:H Thin Films
Authors: King Sean , Bielefeld Jeff
Published: October 2010

Plasma Enhanced Chemically Vapor Deposited SiC:H thin films are compelling materials for both semiconductor nano-electronic and MEMS/NEMS technologies due to the extreme chemical inertness of this material and the ability to tune a variety of material properties across an extreme range of values. As one example of the latter, we demonstrate that using PECVD the dielectric constant and Young's modulus of SiC:H thin films can be varied from < 3 to > 7 and < 10 GPa to > 200 GPa respectively. Utilizing Fourier Infrared-Transform Spectroscopy, we show that this remarkable range in materials properties is achieved primarily via the incorporation of terminal hydrogen groups which lowers the overall connectivity of the Si-C network bonding. We find that once the average network coordination number for Si and C falls below 2.6, the SiC network becomes under constrained and there is a loss of rigidity percolating through the system thus limiting the range of materials properties that can be achieved in this system.
(Invited) Integrated Perfusion Culture Microchamber Array Chip for High-Throughput Drug Dose Response Assay
Authors: Sugiura Shinji , Hattori Koji , Kanamori Toshiyuki
Published: October 2010

We report a perfusion culture microchamber array chip for high throughput drug dose response assays. The microchamber array chip was equipped with a serial dilution microfluidic network for generating a logarithmic concentration profile. Cell suspension, drug solution and media were introduced into the liquid reservoir with a micropipette. The dose response assay was carried out by applying the appropriate pressure through the air vent filters. The dose response of a model anti cancer drug, paclitaxel, on HeLa cells were successfully evaluated by the fluorescent image analysis in the microchamber array chip. Also, the accuracy of our microchamber array chip was confirmed to be equivalent to conventional assay plates in dose response assays. The perfusion culture microchamber array chip, with its simple interface and well-designed microfluidic network, will likely become an advantageous platform for future cell-based assay on microchips.
(Invited) Microcantilever Arrays With In-Plane Photonic Readout for Biosensing
Authors: Nordin Gregory P. , Kim Seunghyun , Hu Weisheng , Anderson Ryan , Noh Jong Wook , Ness Stan , Dahlquist William , Richards Daniel
Published: October 2010

We review progress toward microcantilever arrays with in-plane photonic readout for biosensing applications. Microcantilever arrays are fabricated on individual silicon-on-insulator (SOI) chips and integrated with two-layer polydimethylsiloxane (PDMS) microfluidics that incorporate fluid channels and valves. Microcantilever functionalization is accomplished by inkjetting appropriate fluids onto one side of each cantilever. Preliminary biosensing results using the streptavidin-biotin model system are discussed.
Microelectrode Array Supported by Microfluidic Channel for High-Throughput Sensing: Fabrication and Characterization
Authors: Delcourt Lançon Alice , Kataky Ritu , Wood David , Gallant Andrew J.
Published: October 2010

The fabrication and characterisation of a microelectrode array supported by microfluidic channels for electroanalytical application are described in this paper. An array of 306 gold recessed microelectrodes (45 µm diameter) was fabricated using lithography, metallisation and oxygen plasma treatment processes. Electroplating and electron-beam metallisation of the electrodes resulted in different surface roughness values. Characterisation of the electrodes showed that those roughness differences had an influence on the response of the array. The array activity was improved by increasing the surface roughness from 0.88 nm to 9.76 nm. Microdevice characterisation, using cyclic voltammetry showed well behaved microelectrodes.
High Toughness and Moisture Insensitive Hydrogenated Amorphous Silicon Carbide Films for MEMS/NEMS
Authors: Matsuda Yusuke , King Sean , Bielefeld Jeff , Dauskardt Reinhold
Published: October 2010

This study investigated the fracture properties of hydrogenated amorphous silicon carbids (a-SiC:H) thin films for NEMS/MEMS. Fracture energy of these films decreased with decreasing Young's modulus. However, we found a surprisingly high fracture energy of a low Young's modulus film, which was rationalized by the onset of plasticity. These films exhibited little sensitivity to moisture-assisted cracking significantly different from silica based materials, which will be a significant advantage of a-SiC:H films for applications employed in harsh environments.
Characterization of Thermo-Mechanical Properties of Carbon-Based Low-Dimensional Material/Metallic Thin-Film Composites from NEMS Structures
Authors: Cho Myung Rae , Kim Young Duck , Lee Byung Yang , Hong Seunghun , Park Yun Daniel
Published: October 2010

We report on the direct thermal conductivity measurement of nanoscale nanolaminate material system from metallic thin-film (Al) and carbon-based low-dimensional material (swCNT). Such accurate measurement was made possible by realizing submicron measurement platform using micromaching techniques. Furthermore, by measuring the resonant response of such nanomechanical structures, we are able to deduce their thermal-elastic properties. We find that addition of swCNTs to Al thin-film greatly suppresses the overall coefficient of thermal expansion. On the other hand, addition of swCNTs has marginal effects on the resulting thermal conductivities.
Wafer Level Characterization of the Sacrificial HDP Oxide Lateral Etching by Anhydrous Vapor HF with Ethanol Vapor for SiGe MEMS Structures
Authors: Cui Hushan , Van Hoof Rita , Severi Simone , Witvrouw Ann , Knoops An , Delande Tinne , Pancken Joris , Claes Martine
Published: October 2010

In this work, the lateral etching of the sacrificial high density plasma (HDP) oxide by anhydrous vapor HF (AVHF) together with ethanol vapor is characterized for SiGe microelectro-mechanical systems (MEMS) structures. An extensive design of experiment (DOE) is carried out to study the impact of the process conditions on etch rate (ER) and within wafer uniformity (UWiW). Two wafer level automated techniques, critical dimension scanning electron microscopy (CD SEM) and high resolution profiler (HRP), are compared to replace the manual inspection method performed at die level. It is found that each 25Torr increment in process pressure doubles the ER in the 75 Torr - 125 Torr range. Each 150sccm increment in AVHF flow rate increases the ER 1.3~1.5 times in the 300 sccm - 600 sccm range. Based on the reproducible ER (~80 nm/min) and the UWiW (~10%) of the process of record (POR) as measured by CD SEM, a statistical process control (SPC) is set up for this process condition.
Photopatternable Electrical Conductive Ag- SU-8 Nanocomposite for MEMS/MST
Authors: Khosla Ajit , Gray B.L.
Published: October 2010

An electrically conductive SU-8 has been formulated and can be used to build micro-components for MEMS, microfluidics and packaging applications. SU-8 is an insulating near -UV negative-tone photoresist. An electrically conductive SU-8 has been formulated and can be used to build micro-components for MEMS, microfluidics and packaging applications. In order to enhance the electrical conductivity of SU-8, silver nanoparticles with an average diameter of 80nm were dispersed by ultrasonic agitation. The resulting nanocomposite was successfully patterned. Evolution of electrical conductivity of SU-8 as a function of weight percentage has been studied. It is observed that the conductivity increases slowly up to 2.2 wt% weight concentration. However, after this point the conductivity increases rapidly. This behavior of conductivity variation can be explained in terms of the percolation theory. At lower concentrations of silver nanoparticles, percolation paths are not set up by the nanoparticle network. As the concentration of nanoparticles in the composite increases, the percolation paths via conducting nanoparticles are set up. At this stage, the nanoparticles control the conductivity of the nanocomposite matrix.
Electrodeposition Assisted X-ray Lithography: Single Step Approach
Authors: Katsoudas John , Timofeeva Elena V. , Segre Carlo
Published: October 2010

This paper reports on the development of a novel single-step approach for the formation of patterned metal deposits using X-ray lithography. It is based on simultaneously exposing the substrate to masked X-rays within an electric field, utilizing the effects of radiolysis and potentiostatic electrodeposition. In the LIGA process a thick photo resist is exposed to a masked off X-ray beam and the processed resist is used as an electroplating template. Minimization of as many processing steps as possible would make the process a much more efficient and cost effective technique. The traditional molding and electroplating steps were marked for deletion in our proof of concept experiment, because of the beam time and effort that is required in manufacturing a LIGA mold. The method that is presented forgoes 4 traditional steps involved in fabricating high aspect ratio structures. We provide a proof of principle for single step patterning with x-ray lithography.
Design Approach and Realization of Integrated Silicon Piezoresistive Pressure Sensors for Wide Application Ranges
Authors: Schreiber-Prillwitz Wolfgang , Saukoski Mikko , Chmiel Gerhard , Job Reinhart
Published: October 2010

We discuss the consequent application of the theory of piezoresis-tivity with regard to the optimization of monolithic integrated pres-sure sensor family designs, based on CMOS technology. The achievement of a sufficient signal for the given signal conditioning, as well as mechanical stability of the membrane, were the primary goal of the investigation. A rigorous systematic approach is essential since limiting boundary conditions for certain parameters of the sensor design occur. Based on structural analysis of the sensor model, and self written MATLAB signal extraction scripts, the design of the new pressure sensor product family was investigated. Main focus was the achievable sensitivity under the constraint of the feasible mechanical fracture limit - mechanical overload - of crystalline silicon of below 700MPa. Hence, the allowed range of the thickness deviation per pressure range of the silicon mem-brane was deduced. Experimental verification shows a very good matching between measurements and simulations results.
Research Advances towards Low Cost, High Efficiency PEM Electrolysis
Authors: Ayers Katherine E. , Anderson Everett B. , Capuano Christopher , Carter Blake , Dalton Luke , Hanlon Greg , Manco Judith , Niedzwiecki Michael
Published: October 2010

Water electrolysis has benefits over other hydrogen generation technologies due to the lack of carbon footprint when integrated with a renewable source of energy. Specifically, proton exchange membrane (PEM) electrolysis is a promising technology for hydrogen generation applications because of the lack of corrosive electrolytes, small footprint, and ability to generate at high pressure, requiring only deionized water and an energy source. PEM electrolysis also produces very pure hydrogen, with none of the typical catalyst poisons that may be found in hydrogen produced from reforming. However, significant advances are required in order to in order to provide a cost-competitive hydrogen source for energy markets. This paper will discuss the current limitations and recent work by Proton Energy Systems towards reaching the DOE Hydrogen Program objective for distributed production of hydrogen from distributed water electrolysis of $3.70/gge by 2012.
Alkaline Electrolytes and Reference Electrodes for Alkaline Polymer Electrolyte Membrane Fuel Cells
Authors: Kizewski Jamie , Mudri Nurul , Zeng Rong , Poynton Simon , C. T. Slade Robert , Varcoe John R.
Published: October 2010

This article presents an introduction to the state-of-the-art understanding and recent developments [publicly available] of alkaline polymer electrolyte membrane fuel cells. The major issues with the characterization of alkaline anion-exchange membranes (including radiation-grafted types) and the development of a practical in situ reference electrode system will also be discussed.
Electro-Catalysis of Oxygen Reduction Reaction
Authors: Rossmeisl Jan , Tripković Vladimir , Tritsaris George A. , Calle-Vallejo Federico
Published: October 2010

This paper is a short review of the recent developments in understanding trends in electro-catalysis of the oxygen reduction reaction (ORR). Our focus is on atomic scale simulations at the density functional theory level. First, we investigate the models and the approximations that have been assumed, and thence we reach the conclusion that trends in electrocatalysis are well captured by only considering binding energies of reaction intermediates to the catalyst surface. We show, assuming a simple and very likely series of intermediates, existence- of a universal scaling relation common to all ORR catalysts, which defines the overpotential.
Electrochemical AFM Investigations of Proton Conducting Membranes
Authors: Hink Steffen , Aleksandrova Elena , Roduner Emil
Published: October 2010

Perfluorinated, s-peek and s-ppek polymer electrolyte fuel cell membranes are investigated using electrochemical atomic force microscopy. The proton conductivity and the topography are measured simultaneously at a nanoscale resolution. The results are compared with those of Nafion, and significant differences in the proton conductivity are revealed. The hydrocarbon membranes show a small overall conductivity and not the typical conductive and non-conductive regions as observed for Nafion. For the s-peek membrane an anti-correlation between the topography and the conductivity is observed. One type of the perfluorinated membranes in principle behaves similar to Nafion, whereas another type behaves more similar to the hydrocarbon membranes. This suggests that the manufacturing process plays an important role for the morphology of the polymers.
Atomic Layer Deposition of Platinum onto Functionalized Aligned MWNT Arrays for Fuel Cell Application
Authors: Bult Justin , Dameron Arrelaine , Pylypenko Svitlana , Engtrakul Chaiwat , Bochert Christopher , Chen Limeng , Leong Jeremy , Frisco Sarah , Simpson Lin , Dinh Huyen N. , Pivovar Bryan
Published: October 2010

High aspect ratio materials, such as carbon nanotubes (CNTs), provide unique opportunities and advantages as catalyst support materials in fuel cells. In particular, CNTs are highly conductive and corrosion resistant; properties which represent limitations for current carbon supports. While most advanced catalysts research focuses on the production of small nanoparticles to increase the percent of surface accessible Pt; here, we specifically attempt to conformally coat Pt in thin layers onto CNT arrays. We present our work on modifying CNT surfaces inside high-density, surface-bound aligned CNT arrays (aspect ratio ~1:750) with non-toxic gas phase chemistries. The number of nucleation sites and the onset of growth of Pt by ALD can be tuned by using Ar plasma, O2 plasma and chemical functionalization. This, in turn, affects the uniformity of the Pt ALD coating down the length of the tubes within the CNT array.
Analysis of the Relation between Oxidation State and ORR Activity of Pt by Linear Sweep Voltammetry
Authors: Nagai Tomoyuki , Murata Hajime , Morimoto Yu
Published: October 2010

Platinum oxide grown by potential cycles or hold was analyzed using linear sweep voltammetry, and its influence on the oxygen reduction reaction (ORR) was investigated using a carbon-supported Pt nano-particle catalyst. Two types of platinum oxides having different reduction potentials were identified and their amounts and ratio were found to depend on the applied potential history. The ORR current decreased linearly with increase in the total amount of the platinum oxides, regardless of the types of the platinum oxides.
Stable Oxygen Reduction Electrocatalysts from Presynthesized PdPt Nanoparticles on Carbon
Authors: Slanac Daniel A. , Li Lin , Stevenson Keith J. , Johnston Keith
Published: October 2010

We have synthesized an oxygen reduction catalyst composed of pre-synthesized Pd3Pt2 alloy nanoparticles dispersed on Vulcan carbon. Transmission electron microscopy (TEM) and X-ray diffraction (XRD) indicate the alloy particles are 4.0nm. The catalyst loses 20% of its activity after potential cycling from 0.5 V to 1.2 V (NHE) in HClO4 compared to 70% for commercial Pt/VC. Even after 20% loss, the final activity of the Pd3Pt2/VC catalyst is 0.095 A/mgPt, equal to that of the fresh commercial Pt/VC. After cycling TEM shows only a small increase in particle size to 4.5nm, and X-ray photoelectron spectroscopy reveals no change in the oxidation states of the metals, indicating the stability may result from an increased dissolution resistance of the alloy relative to the base metals. The development of well-defined, stable, and active alloy catalysts facilitates a better understanding of structure-activity relationships and is encouraging for the application of commercially viable fuel cells.
Electrochemical and DFT Analysis of Deactivation of Pt Supported on Niobia
Authors: Konopka Daniel , Kiefer Boris , Jiang Ying-Bing , Ward Tim , Atanassov Plamen
Published: October 2010

The catalytic deactivation of platinum supported on NbRuyOz mixed metal oxide support has been investigated. 60% Pt/NbRuyOz was synthesized in a single step using spray pyrolysis, followed by reductive thermal post-treatment. The catalyst was deposited onto a tabbed, Au TEM grid and rapidly cycled between anodic and cathodic potentials in 0.1M HClO4 and 1M KOH to observe mechanisms of corrosion and deactivation. After 3600 cycles, TEM shows a thin film of oxygen-rich niobia with the potential to block ion transport covering the catalyst and support particles. Density Functional Theory calculations indicate that the rate of oxygen diffusion across the Pt(111) surface is in good agreement with experimental observations of the period of catalyst deactivation (several weeks) when exposed to open atmosphere. This suggests that the mechanism of catalytic deactivation could involve the capture and release of oxygen as Nb2O5 breaks down into reduced fragments of NbOx.