bluuebunny/crossref_metadata_2025 huggingface dataset:
Dissolution Kinetics of Nickel in Lead-free Sn-Bi-In-Zn-Sb Soldering Alloys
Authors: Barmak Katayun , Berry David C. , Khoruzha Vira G. , Meleshevich Kostyantyn A. , Dybkov Vasyl I.
Published: April 2011

The dissolution process of nickel in liquid Pb-free 87.5% Sn-7.5% Bi-3% In-1% Zn-1% Sb and 80% Sn-15% Bi-3% In-1% Zn-1% Sb soldering alloys has been investigated by the rotating disc technique at 250-450°C. The temperature dependence of the nickel solubility in the solders obeys a relation of the Arrhenius type cs = 4.94 × 102 exp (-39500/RT) % for the former alloy and cs = 4.19 × 102 exp (-40200/RT)% for the latter, where R is in J mol-1 K-1 (8.314 J mol-1 K-1) and T in K. The solubility values of nickel in the alloys differ considerably, while the dissolution rate constants are rather close. The data presented can be used to evaluate (i) the thickness of the dissolved portion of the solid nickel material during soldering, (ii) the extent of saturation of a solder with nickel and (iii) the effect of dissolution on the growth rate of intermetallic layers at the Ni-solder interface.
Arsenic in ZnO and GaN: Substitutional Cation or Anion Sites?
Authors: Wahl Ulrich , Correia Joao Guilherme , Rita Elisabete , Marques Ana Claudia , Alves Eduardo , Soares Jose Carvalho , Isolde Collaboration The
Published: April 2011

Modifying the properties of ZnO and GaN by means of incorporating arsenic impurities is of interest in both of these semiconductors, although for different reasons. In the case of ZnO, the group V element As has been reported in the literature as one of the few p-type dopants in this technologically promising II-VI compound. However, there is an ongoing debate whether the p-type character is due to As simply replacing O atoms or to the formation of more complicated defect complexes, possibly involving As on Zn sites [1]. In the case of GaN, the incorporation of high concentrations of As has been studied with respect to the formation of GaAs(x)N(1-x) alloys and the related modification of the GaN band gap and its luminescence behaviour. It has been suggested that As in GaN is amphoteric, with its lattice site preference depending on the doping character of the material, i.e. mostly substitutional Ga in p-type but also substitutional N in n-type [2].

We have determined the lattice location of implanted As in ZnO and GaN by means of conversion electron emission channeling from radioactive 73As. In contrast to what one might expect from its nature as a group V element, we find that As does not occupy substitutional O sites in ZnO but in its large majority substitutional Zn sites [3]. Arsenic in ZnO is thus an interesting example for an impurity in a semiconductor where the major impurity lattice site is determined by atomic size and electronegativity rather than its position in the periodic system. The results are different in the case of As implanted into GaN, where we found roughly half of the implanted As atoms occupying Ga and the other half N sites. The amphoteric character of As therefore certainly plays a role in explaining the extreme difficulties in growing high quality GaAs(x)N(1-x) alloys with values of x above a few percent.

A preliminary report will also be given on ongoing emission channeling lattice location experiments using radioactive 124Sb in ZnO and GaN.
Predominance of Alternate Diffusion Mechanisms for the Interstitial-Substitutional Impurity Gold in Silicon
Authors: Li Hui , Li Na , Joshi Subhash M. , Tan Teh Y.
Published: April 2011

It is well known that Au indiffusion in Si is dominated by the Kick-Out mechanism governed by Si self-interstitials, with negligible contribution from the Frank-Turnbull mechanism governed by vacancies. In this paper we present modeling and simulation results to show that the Frank-Turnbull mechanism actually dominates Au outdiffusion in Si.
Electronic structure of Cd, In, Sn substitutional Defects in GaSe
Authors: Rak Zsolt , Mahanti Subhendra D , Mandal Krishna C , Fernelius Nils C
Published: April 2011

Ab initio electronic structure calculations within density functional theory have been carried out in pure GaSe and GaSe doped with substitutional impurities (Cd, In and Sn) at the Ga site in order to understand the nature of the defect states and how they depend on the nominal valence of these three impurities. We find that Cd impurity introduces a defect state located between 0.1 – 0.18 eV above the valence band, in good agreement with photoluminescence peaks seen at 0.13 eV and 0.18 eV. Using both experimental and theoretical effective mass parameters we show that effective mass model fails to describe these acceptor states. Sn changes the single particle density of states (DOS) near the bottom of the conduction band, and gives rise to resonant states deep in the valence band. In, on the other hand, behaves like Ga, it does not make noticeable change in the DOS of the host GaSe crystal.
Stress Effects on As Activation in Si
Authors: Ahn Chihak , Dunham Scott T
Published: April 2011

We studied stress effects on As activation in silicon using density functional theory. Based on lattice expansion coefficient, we calculated formation energy change due to applied stress and plotted the stress dependence of AsmV concentration. We found that biaxial stress results in minimal impact on As activation, which is consistent with experimental observation by Sugii et al. [J. Appl. Phys. 96, 261 (2004)], who found no significant change in As activation under tensile stress.
Low-Energy Irradiation Damage in Single-Walled Carbon Nanotubes
Authors: Suzuki Satoru , Kobayashi Yoshihiro
Published: April 2011

We show that low-energy (20 eV–20 keV) electron or photon irradiation extinguishes the characteristic physical and chemical properties of single-walled carbon nanotubes, indicating that the irradiation damages the nanotubes. The irradiation-induced defects convert the electric properties of metallic SWNTs to semiconducting, and the nominal bandgap can be tuned simply by the irradiation dose. The defects also have the following interesting properties. The damage and recovery are reversible, indicating that the number of carbon atoms is preserved. The damage and recovery strongly depend on the diameter, suggesting that the damage is prominent in a rolled up graphene sheet, but not in a planar one. The activation energy of the defect healing is so small, depending on the diameter, that the defects can be healed even at room temperature or below.
Gettering Effect in Low and High Density Structural Defect Regions of the Cast Multi-Crystalline-Silicon Wafer
Authors: Park Yongkook , Lu Jinggang , Rozgonyi G. A.
Published: April 2011

Two cast multi-crystalline silicon (mc-Si) sister wafers before and after solar cell processing were investigated to explore the gettering effect in low and high density structural defect regions. For the processed wafer, the minority carrier recombination lifetime was correlated to the structural defect distribution. For the low density region of as-grown wafer, Cr impurities were 3.28x1013cm-3 and they were reduced to 1.74×1012cm−3 for the processed wafer. The isolated Cr impurities dissolved from the precipitates at 900°C which is the typical gettering temperature in the solar cell processing are getterd effectively in the low density regions. Our current understanding for the gettering effect in the high density regions is that the segregated Cr impurities at defect sites are not released to the silicon matrix at 900°C resulting in the poor gettering effect.
In-situ Infrared Absorption Monitoring of Atomic Layer Deposition of Metal Oxides on Functionalized Si and Ge Surfaces
Authors: Dai Min , Kwon Jinhee , Ho Ming-Tsung , Wang Yu , Rivillon Sandrine , Li Meng , Chabal Yves Jean , Boleslawski Marek
Published: April 2011

The nature of the interface between Si and Ge substrates and high-k dielectrics often controls the performance of MOSFET devices. Precleaning and/or chemical functionalization of the surfaces can dramatically affect the formation of an interfacial layer. We have used in-situ IR spectroscopy to probe the relevant interfaces during ALD growth for a variety of surface treatments, including H- and Cl-termination, and nitridation. This paper focuses on understanding of the mechanisms for interfacial SiO2 (or GeOx) formation during HfO2 growth using tetrakis-ethylmethylamidohafnium (TEMAH) as the metal precursor and water or ozone as the oxygen precursor. We find that impurities arising from incomplete ligand elimination during growth (e.g. OH for H2O processing and CO- and NO-containing species for O3 processing) are incorporated into the HfO2 film during growth. Upon annealing, most of these species react, but can also migrate to the interface. Nitridation of Si and Ge surfaces will in general prevent SiO2 or GeOx formation but can also affect the growth rate.
Preparation of Substrates for IBAD-MgO Coated Conductors
Authors: Matias Vladimir , Hänisch Jens , Rowley E. John , Sheehan Chris , Clem Paul G. , Kumasaka Noriyuki , Kodaka Ichiro
Published: April 2011

We examine the influence of various substrate preparation procedures for ion-beam assist deposition (IBAD) texturing of MgO. IBAD-MgO nano-texturing is very sensitive to the nucleation surface, and surface roughness has an important influence on the texture of the MgO layer. We studied Hastelloy C-276 metal alloy as the substrate. The untreated substrate is leveled by either electropolishing, mechanical polishing or solution deposition. All three methods are applied to continuously moving tapes in long lengths. The RMS surface roughness decreases from 20-50 nm for the untreated substrate to 0.5 nm, 0.3 nm and 1 nm respectively. The in-plane and out-of plane crystalline alignment of the MgO layer improves as the roughness is decreased below 2 nm.
AC Current Driven Flux Dynamics in YBCO Coated Conductors
Authors: Lucarelli Andrea , Yang Ran , Luepke Gunter , Levin George , Haugan Timothy , Barnes Paul
Published: April 2011

We present a time-resolved magneto-optical imaging study of YBa2Cu3O7-δ coated conductors in alternating current regime. The evolution of the magnetic flux density distribution in the superconducting samples is imaged at small steps of the phase of the applied AC current. The flux penetration during the phase evolution is inhomogeneous due to the grain structure of the coated conductor. A quantitative analysis of the images show how grain boundary network affects the overall behavior of the flux and current density evolution.
Pattern Transfer Process Using Innovative Polymers in Combined Thermal and UV Nanoimprint Lithography (TUV-NIL)
Authors: Brunetti Francesca , Harrer Stefan , Scarpa Giuseppe , Lugli Paolo , Kubenz Mike , Schuster Christine , Reuther Freimut
Published: April 2011

We performed combined thermal and ultraviolet nanoimprint lithography (TUV-NIL) using a recently developed nanoimprint polymer (mr-NIL 6000 from Micro Resist technology GmbH) and achieved an imprinted feature size of 50 nm. We used commercially available 2-inch-diameter transparent quartz molds (NIL Technology, Denmark and Obducat, Sweden) comprising 150 nm to 190 nm-deep features of various shapes and aspect ratios with lateral dimensions ranging between 50 nm and 300 nm. The imprint polymer was spun onto a silicon substrate, covered with an oxide layer. After the TUV-NIL step, residual polymer layers at the bottom of the imprinted features were removed by oxygen plasma etching. Imprinted patterns were then transferred into the silicon oxide layer underneath by reactive ion etching (RIE). In a final step the residual polymer was stripped off the silicon oxide surface in an oxygen asher. All imprinted features as well as the corresponding pattern transfer results showed good surface and sidewall characteristics.
3D Photonic Structures by Sol-Gel Imprint Lithography
Authors: Verschuuren Marc , Sprang Hans Van
Published: April 2011

We present a new and relatively simple process to manufacture three-dimensional sub-micron structures over square centimeter areas using a soft stamp imprinting process. The room-temperature replication process shows excellent quality in transferring features directly into inorganic silica material with pattern distortion smaller than 0.03% over an area of 15×15mm2. Using a self assembly planarization method the imprinting process can be repeated to form three-dimensional structures. As a demonstration, a multilayer stack of four crossed gratings is shown.
Adhesion Promoting Photo-Acid Generator APPAG - A New Class of Lithographic Material
Authors: Sharma Shalini , Sharma Geeta , Meagley Robert
Published: April 2011

Photo-acid generator (PAG) is the key component responsible for the increased sensitivity of chemically amplified resists in use today for microelectronics production. Concentration variation of PAG through the thickness of the photoresist film adversely affects materialís performance. To offset reduced acid concentration at the bottom of the resist, we have developed adhesion promoting photo acid generators, called as a class “APPAG” that enhance acid concentration at interface between the resist and the substrate. An overview on the preparation and characterization of two siloxane based APPAG materials along with a performance comparison of commercial DUV and EUV resists on APPAG is provided. Longer diffusion length photo-acid generator (APPAG 9) retained square profile of critical dimension (CD) at off-focus values and was found to give nearly a 50% improvement in depth of focus for 250nm node DUV lithography. For EUV lithography, both shorter diffusion length APPAG 6 and APPAG 9 were shown to substantially improve performance envelope for 100nm dense lines and spaces at reduced post exposure bake (PEB).
Gas Phase Nanoparticle Integration
Authors: Barry Chad R , Kortshagen Uwe , Jacobs Heiko O
Published: April 2011

We report on two gas phase nanoparticle integration processes to assemble nanomaterials onto desired areas on a substrate. We expect these processes to work with any material that can be charged. The processes offer self-aligned integration and could be applied to any nanomaterial device requiring site specific assembly. The Coulomb force process directs the assembly of nanoparticles onto charged surface areas with sub-100 nm resolution. The charging is accomplished using flexible nanostructured electrodes. Gas phase assembly systems are used to direct and monitor the assembly of nanoparticles onto the charge patterns with a lateral resolution of 50 nm. The second concept makes use of fringing fields. The fringing fields directed the assembly of nanoparticles into openings. The fringing fields can be confined to sub 50 nm sized areas and exceed 1 MV/m, acting as nanolenses. Gas phase assembly systems have been used to deposit silicon, germanium, metallic, and organic nanoparticles.
Reliable Suzuki Chemistry For Functionalised Polythiophene Synthesis
Authors: Higgins Simon , Liversedge Iain , Badriya Samer , Heeney Martin , Giles Mark , McCulloch Iain
Published: April 2011

Until recently, the synthesis of polythiophenes using Suzuki chemistry has proven difficult because of the ready protodeborylation of thiophene boronates. However, we now report that the new generation of bulky, electron-rich Pd(0)-phosphane catalysts are effective and reliable for the preparation of regioregular polyalkylthiophenes using Suzuki coupling. Moreover, the monomers can be prepared in high yield by Ir-catalysed borylation, without the need for strong organolithium bases, making this potentially a highly functional group-tolerant approach to polyalkylthiophene derivatives. Perfluoroalkylthiophenes also undergo this reaction.
Development of A First-Responder Fluorescence Reader for Microarray Cytokine Assay of Human Immune Response to Disease
Authors: Fenner David B. , Rosen David I , Ferrante Anthony A , Stevens Amy E , Bigelow Chad E , Davis Steven J
Published: April 2011

Development of field portable apparatus and methods for cytokine assay of human saliva by fluorescent-reporting microarray plates is described. Multiplexed assay of 12 cytokines for minimally-processed saliva is read with a CCD-based imager under LED excitation. Immune responsive cytokines are measured at levels significant for indication of human disease state. The motivational context for the new apparatus development, the general optical design issues, saliva protocol, and image analysis are described.
Bicolor (Red-Yellow) Fluorescence Patterning in Polymer Film Based on Phthalimido Carbamate as a New Group of Photobase Generator
Authors: Chae Kyu Ho , Kim Yoo Ho
Published: April 2011

Bicolor fluorescent micro-pattern in the polymer film was prepared through the use of a new group of photobase generator containing phthalimido carbamate groups. The photobase generation from phthalimide carbamates was studied from the product analysis of a model compound. The result indicates that amine was produced from the photolytic cleavage of the CN bond of the phthalimide carbamate group. Bicolor fluorescent micropatterns were obtained by treating a copolymer film containing phthalimido groups, which was irradiated with 254 nm UV light through photomask, with fluorescamine and rhodamine, consecutively. Various colored fluorescent micropatterns – green, red, or red-yellow, were obtained on a single polymer film by varying the excitation wavelength.
Some Advances in Liquid Crystal Elastomers: From Crosslinks Affected Ordering to Carbon Nanoparticles Enabled Actuation
Authors: Zumer Slobodan , Chambers Martin , Cordoyiannis George , Finkelmann Heino , Kutnjak Zdravko , Lebar Andrija , Remskar Maja , Zalar Bostjan
Published: April 2011

Liquid crystal elastomers (LCE) exhibit a combination of elasticity and mesogenic ordering, yielding large thermally stimulated changes in shape. These LCE systems although well characterised, still yield open questions in the nature of how the crosslinking affects the LCE phase transition. Therefore calorimetry and deuteron-nuclear magnetic resonance were used to study the isotropic-nematic phase transition of uniformly ordered LCE. We observed that the density of crosslinkers strongly affects the nematic-isotropic phase transition. The observed spread critical transitions are explained with a dispersion of local mechanical fields that yields a weakly disordered orientational state composed of regions that exhibit temperature profiles of the nematic order parameter ranging from first order to supercritical. On increasing crosslinking density, the predominantly first order thermodynamic response transforms into a predominantly supercritical one.

Additionally, to illustrate the response of these actuating systems, it was demonstrated that a LCE can be electrically heated. The insulating LCE network was reprocessed using conducting nanoparticles dispersed in a solvent with high LCE swelling capability. This results in a low electrical resistivity surface layer of LCE network with a high concentration of conducting nanoparticles. The reprocessing allows the effective resistivity of a LCE film to be reduced from highly insulating values to values useable for electrical actuation. This layer in addition withstands large changes in geometrical shape both in contraction and expansion. Utilizing a resistive “Joule” heating effect, the reprocessed system exhibits an indirect electromechanical effect characterised by a 150% length change that can be cycled for more than 10, 000 times.
Crosslinking High Free Volume Polymers - Effect on Gas Separation Properties
Authors: Shao Lei , Samseth Jon , Hagg May-Britt
Published: April 2011

Crosslinkable nanoparticle-filled poly(4-methyl-2-pentyne) [PMP] membranes were cast from carbon tetrachloride solutions containing PMP, hydrophobic fumed silica, and 4,4¡¯-(hexafluoroisopropylidene)diphenyl azide [HFBAA]. The composite membranes were crosslinked by UV irradiation at room temperature. Low levels of the bis azide were effective in rendering the membranes insoluble in cyclohexane and carbon tetrachloride, both good solvents for PMP. The process is simple and effective, and thus PMP can be easily converted to mechanically stable membranes. Compared to the pure PMP membrane, the permeability of the crosslinked membrane is initially reduced for all tested gases due to the crosslinking. By adding nanoparticles, the permeability is again increased, crosslinking is successful in maintaining the permeability and selectivity of PMP over time.
Functionalized Nanoparticles for Composite Polymer Electrolyte
Authors: Toussaint Gilles , Henrist Catherine , Detrembleur Christophe , Jerome Robert , Cloots Rudi
Published: April 2011

The covalent grafting of low-molecular weight poly(ethylene glycol) (PEG) onto high surface silica nanoparticles (Cab-O-Sil EH5) has been accomplished by a multi-step reaction. Reaction involved PEG attachment by epoxide-terminated ring opening of a sylilation agent previously grafted. A maximum grafting density of 0.42 PEG per nm2 has been determined by thermogravimetric analysis (TGA). Differential scanning (DSC) calorimetry confirmed the modification of silica after reaction. Infra-Red (IR) analysis and Carbon-13 Magic Angle Spinning Nuclear Magnetic Resonance (13C MAS NMR) confirmed PEG fixation and opening of the epoxide ring.
Laddersiloxanes: Silsesquioxanes with Defined Ladder Structure
Authors: Unno Masafumi
Published: April 2011

A series of structurally-defined laddersiloxanes [1] are presented. Pentacyclic laddersiloxanes were prepared by a stepwise procedure from all-cis-tetraisopropylcyclotetrasiloxanetetraol. All-anti pentacyclic, tetracyclic, tricyclic, and bicyclic laddersiloxanes were obtained by oxidation from respecting all-anti pentacyclic ladder polysilane. Stereocontrolled approach using RS-disiloxanediol as an expanding unit enabled the synthesis of longer laddersiloxanes. Finally, methyl-substituted ladder polysilsesquioxane was obtained by the stepwise transformation from (MePhSiO) 4. The X-ray crystal structures, NMR and IR spectra, and thermal stability of these laddersiloxanes are summarized.
New Generation of Hybrid Organic-Inorganic Macrocellular Foams: Integrative Chemistry Toward Reaching Multifunctional Materials
Authors: Ungureanu Simona , Deleuze Hervé , Birot Marc , Sanchez Clément , Backov Rénal
Published: April 2011

The elaboration of organosilica based hybrid monoliths exhibiting a hierarchically structured bimodal porous structure with tunable functionality have been processed via High Internal Polymeric Emulsion (HIPE) process for the first time. Through one pot synthesis, many organic functionalities that can act as network modifiers (Methyl, Dinitrophenylamino, Benzyl, Mercaptopropyl) or co-network formers (Pyrrol) have been anchored to the amorphous silica porous network. The resulting materials have been thoroughly characterized via a large set of techniques SEM, TEM, SAXS, mercury porosimmetry, nitrogen adsorption isotherms, FTIR, 29Si MAS NMR. These sol-gel derived hierarchical open cell functional hybrid monoliths exhibit macroscopic void spaces ranging from 5 up to 30 [.proportional]m and their accessible micro-mesoporosity, reveal hexagonal organisation for the dinitrophenylamino, benzyl, and pyrrol based hybrids. The average condensation degree for these hybrid networks ranges between 86 and 90% yielding shaped monoliths with both good integrity and sufficient mechanical properties to be usable as functional catalytic or chromatographic supports.
Mesoporous Silica and Titania by Glycol-Modified Precursors
Authors: Geserick Jasmin , Hüsing Nicola , Roßmanith Renate , Weiss Clemens K. , Landfester Katharina , Denkwitz Yvonne , Behm R. Jürgen , Hörmann Ute , Kaiser Ute
Published: April 2011

Ethylene glycol modified precursors, such as tetrakis(2-hydroxyethyl)orthosilicate (EGMS) or bis(2-hydroxyethyl)titanate (EGMT), have distinct advantages in the synthesis of mesoporous materials by sol-gel processing compared to the commercially available tetraalkoxide precursors. The glycols released upon hydrolysis have proven to be compatible with lyotropic surfactant mesophases and in addition, these precursors allow for processing in purely aqueous conditions. Besides the standard characterization of the resulting titania and silica-based materials by XRD, electron microscopy, and nitrogen sorption, the potential of the titania-based materials for catalytic applications was tested using Au/TiO2 catalysts in low temperature CO oxidation reactions.
Versatile Hybrid Polymers as Matrices for Nanoparticle Preparation
Authors: Feldgitscher Claudia , Ivanovici Sorin , Kickelbick Guido
Published: April 2011

Hybrid inorganic-organic polymers were prepared applying poly(ethylene oxide) (PEO) crosslinked polysiloxanes as a matrix for the precipitation of metal or metal oxide nanoparticles. Polysiloxanes as flexible and hydrophobic polymer backbones were crosslinked with end-group functionalized PEO by using Pt-catalyzed hydrosilation reactions. Systematic variation of the chain length of the different components resulted in tunable matrices with adjustable hydrophilic regions. The chemical nature of the polysiloxane backbone and the thermal stability of the crosslinked polymer system facilitated nanoparticle preparation through different mechanisms.

The crosslinked hybrid polymers were infiltrated with solutions of lanthanide salts, cobalt carbonyl or HAuCl4allowing the application of three different chemical methods (hydrolysis, thermal decomposition, reduction) for nanoparticle preparation. FT-IR, SEM and TEM analyses were used to characterize the insoluble hybrid systems.
Improvements on Flame Retardant Properties of PET/Montmorillonite Nanocomposite Caused by Polyborosiloxane
Authors: Huo Yue , Fan Qinguo , Dembsey Nicholas A , Patra Prabir K
Published: April 2011

A phenyl-containing highly cross linked polyborosiloxane (PBSiO) was synthesized as a flame retardant for polyethylene terephthalate (PET). We coated montmorillonite (MMT) clay, a very high aspect ratio and high specific surface area layered silicate with synthesized PBSiO to introduce synergism in flame retardation to the PET nanocomposite film that retained thermal and mechanical properties. This PBSiO has high thermal stability at the processing temperature (270-285° C) of PET and acts as a compatibilizer between PET and clay that are otherwise incompatible. During burning, the flame retardant PET containing PBSiO and MMT forms a protective borosilicatecarbonaceous intumescent char on the surface. Cone calorimeter tests were performed to evaluate key fire properties of the PET/PBSiO/MMT. The peak heat release rate (PHRR) of PET that contains 5 wt% PBSiO and 2.5 wt% MMT was reduced by 60% and similar trend in the reduction of mass loss rate of the nanocomposite was observed.
Hybrid Nanocomposites Based on Metal Oxides and Polysiloxanes with Controlled Morphology
Authors: Ivanovici Sorin , Rill Christoph , Feldgitscher Claudia , Kickelbick Guido
Published: April 2011

Hybrid materials based on polysiloxanes and metal oxides (SiO2, TiO2, ZrO2) were prepared by hydrosilation of allyl acetoacetate (AAA) modified metal alkoxides (M(OR)4; M = Ti, Zr; R = ethyl, isopropyl) or vinyl triethoxysilane with poly(dimethylsiloxane-co-hydrosiloxane) (PDMS-co-PMHS). The obtained compounds acted as single-source precursors in the sol-gel process. Various spectroscopic methods showed the complete functionalization of the polysiloxane chains with the complexes. When alcohols were used as solvents in the sol-gel process, hybrid nanoparticles were obtained, as observed by dynamic light scattering (DLS) measurements, transmission electron microscopy (TEM), and spectroscopic methods such as NMR and FT-IR.
PECVD Silicon Carbide as a Thin Film Packaging Material for Microfabricated Neural Electrodes
Authors: Hess Allison , Parro Rocco , Du Jiangang , Dunning Jeremy , Scardelletti Maximillian , Zorman Christian A.
Published: April 2011

This paper reports our effort to develop amorphous silicon carbide (a-SiC) films for use as hermetic thin film coatings for mechanically-flexible neural electrodes. In our work, the a-SiC films were deposited by plasma enhanced chemical vapor deposition (PECVD) using two distinct methods, namely a single precursor approach using trimethylsilane, and a dual precursor approach using methane (CH4) and silane (SiH4). The mechanical properties of films deposited on Si substrates were characterized using the wafer curvature and load-deflection methods. The effectiveness of the films as moisture barriers for polyimide substrates was characterized by measuring the leakage currents of SiC-coated interdigitated electrode structures soaked in PBS. A microfabricated prototype of the flat interface nerve electrode (FINE) based on a flexible polyimide substrate and a PECVD SiC capping layer was fabricated using a monolithic process based on conventional micromachining techniques. To facilitate this approach, a reactive ion etching process was developed that exhibited high etch rates and high selectively to the SiC films.
Characterization of Degradation Mechanisms in Neural Recording Electrodes
Authors: Anton Jennifer M. , Hooker Stephanie A.
Published: April 2011

Understanding the nature of specific neural activity is essential to the progression of research in the field of brain disorders and diseases, as well as neuroprosthetics. Microelectrodes are the primary measurement devices used to transduce neural activity into electrical signals to help neuroscientists study dynamic brain function. Advances in signal processing and packaging currently allow neural recording for periods as long as a year by use of chronically implanted electrodes in freely behaving animals. Stability of the electrode impedance is required for optimum signal recording over the length of the recording interval. While electrode–tissue interaction plays a major role in the quality of the recorded signal, delamination or degradation of the dielectric coating also interferes with signal recording. Therefore, to improve the signal recording process, it is useful to understand how the electrode design and component materials affect the signal over the course of time.
Morphology and Stretchability of Thin Film Metal Conductors on Elastomeric Substrates
Authors: Tsay Candice , Graudejus Oliver , Jones Joyelle , Lacour Stephanie P. , Wagner Sigurd
Published: April 2011

Fabrication of biomedical devices and components on soft, elastomeric substrates is a promising step toward mechanically-matched and conformal biological-electrical interfaces. However, while polymeric substrates are extremely deformable, electronic materials typically are not. To explore this convergence of stiff electronic materials and compliant elastomers, we prepare thin film gold conductors on polydimethylsiloxane (PDMS) membranes (Fig. 1), which have Young's modulus, E ~ 2 MPa. The gold conductors have the property of remaining electrically conducting while stretched uni-axially to 20% strain and more [1]. Varying the fabrication methods affects the initial microstucture and morphology of the metal films, which in turn determine stretchability. To examine this effect, tensile tests are performed to measure electro-mechanical behavior, and scanning electron microscopy is used to observe the morphology of the films. In this study, we compare metal deposition techniques as well as samples of various metal thicknesses, linking resulting film morphologies to stretchability.
BaZrO3Thin Films For Humidity Gas Sensor
Authors: Chen XiaoXin , Sorenson Michael , Butler Clayton , Rieth Loren , Miller Mark S. , Solzbacher Florian
Published: April 2011

Microscale (MEMS) gas sensing devices for power plant and automobile exhaust gas are being developed. Bulk BaZrO3 has been previously found to be sensitive to H2O at high temperatures, but was never studied in a thin film form. This research thrust focuses on undoped BaZrO3 and doped BaZrO3 with Y.

Thin films were deposited on oxidized n-type silicon substrates at room temperature from ceramic targets with an Ar sputtering ambient. Various deposition pressures and deposition powers were used for the initial investigation. The structural and electrical properties of the deposited films were characterized to investigate their relationships to the deposition process parameters. X-ray diffraction (XRD) was used to measure the crystal structure of the deposited films, and in particular was used to determine if any crystallographic texture is present in the films. XRD results indicate the as-deposited films are amorphous before annealing. Films sputtered with and without oxygen in the ambient were compared. The crystal structure and morphology of BaZrO3 and BaZrO3 doped with Y after annealing were also determined. The materials changed from amorphous to crystalline after annealing at temperatures of 800 °C and 1000 °C for 3 hours in forming gas (2% H2 balanced with Ar gas) and oxygen. Temperature was found to dominate over deposition conditions in determining the final film structure. Atomic force microscopy was used to examine the morphology of the thin films. Gas sensor test structures using a Pt thin film metallization for interdigitated electrode structures were fabricated for gas sensing measurements. The experiments with the completed test structures measured the materials¡¦ resistivity as a function of temperature and gas concentration. Both materials decrease in resistance with increasing temperature, which is consistent with ionic conduction. Some experiments tested the gas sensitivity and selectivity of the films to the target gas H2O vapor (humidity) and possible cross sensitive gases H2 and CO2. Both materials need further development to evaluate their suitability for thin film sensors. First, the films were found to be highly resistive, making characterization of the electrical properties very difficult. Second, O2 ambient annealing gas will be applied to compare the crystal structure and morphology of both films with an Ar ambient annealing process.
P3HT:PCBM Bulk Heterojunction Solar Cells: Morphological And Electrical Characterization And Performance Optimization
Authors: Aernouts Tom , Vanlaeke Peter , Haeldermans Ilse , D'Haen Jan , Heremans Paul , Poortmans Jef , Manca Jean V.
Published: April 2011

The performance of organic solar cells based on the blend of regioregular poly(3-hexylthiophene) (P3HT) and phenyl-C61-butyric acid methyl ester (PCBM) is strongly influenced by the morphology of the active layer on the nanoscale level. X-ray diffraction (XRD) and Transmission Electron Microscopy (TEM) measurements show that ordering of P3HT plays a key role in optimizing the photovoltaic performance. It is demonstrated that the natural tendency of regioregular P3HT to crystallize is disturbed by the addition of PCBM. The crystallinity of the photo-active blend is typically restored by an annealing procedure resulting in improved device performance, characterized by a spectral broadening of the optical absorption.

The morphological changes upon annealing of the P3HT:PCBM blends are accompanied by electrical changes as shown in charge carrier mobility measurements. Space-charge limited current measurements have been performed in hole-only devices with various P3HT:PCBM blend ratios. The mobility before and after annealing is compared and from temperature dependent measurements the width of the density of states distribution (DOS) is determined. The hole mobility in pristine P3HT remains practically unaffected by the annealing treatment. The as-produced P3HT:PCBM blends on the other hand, with a more disordered P3HT phase, have a much lower hole mobility. Annealing is capable of increasing the P3HT ordering with as a result an orders of magnitude larger hole mobility, approaching the value found in pristine P3HT. The DOS bandwidths are affected similarly. In the as-produced blend films a value of 100 meV is found, larger than in the annealed films, there reaching a value around 70 meV similar as in pristine P3HT. Variation of the processing solvent demonstrated however that an optimized morphology and charge transport situation can also be obtained without an additional annealing step. It is shown that in that case the as-produced active layer has already a favorable crystalline morphology. We argue that the high boiling point of the solvent plays an important role in this by influencing the evaporation speed during deposition of the photo-active blend. Further proof is delivered that indeed slowing down the evaporation speed can beneficially influence the solar cell performance. Power conversion efficiency over 4% has been achieved in this way.
Simulation and Fabrication of Two Dimensional Nonlinear Photonic Crystals using Barium Titanate Thin Films
Authors: Lin Pao Tai , Liu Zhifu , Wessels Bruce W.
Published: April 2011

Photonic crystal (PhC) can potentially result in enhanced optical properties around critical points in the photonic band gap. Of interest here are enhanced nonlinear optical effects. In this study, one and two dimensional nonlinear PhC were designed and fabricated using barium titanium oxide (BTO) thin films as the active medium. Nonlinear PhC made with barium titanate thin films potentially provide integrated devices with the advantages of wide tunability and high stability. Films 500 nm thick deposited on MgO substrates were utilized. Two dimensional PhC structures were defined by focused ion beams (FIB). Before patterning, a thin metal layer was deposited on the barium titanate layers in order to improve the conductivity of the samples. After writing the patterns, cylindrical air holes were generated in the thin film layers. The PhC lattice constant and the hole radius were selected in sub-micron region in order to satisfy the requirement of wave resonance. The PhCs with sub-micron features were characterized by the atomic force microscopy (AFM), scanning electron microscopy (SEM), and near field optical microscopy (NSOM). The transmission spectra of the PhC waveguides were calculated with a continuous wide band source that covered 1 to 2 micron wavelength. Simulations of the transmission characteristics were performed using the two dimensional finite difference time domain method (FDTD).
Carbon Nanotubes as Optical Materials
Authors: Lu Shaoxin , Shao Ning , Liu Ye , Panchapakesan Balaji
Published: April 2011

This paper discusses some of the highly interesting effects that occur when photons interact with carbon nanotubes. From position dependent photoconductivity of nanotube thin films to photon induced elastic actuation of carbon nanotubes is presented. A new field of micro-opto-mechanical systems (MOMS) is envisioned through the miniaturization of nanotube actuators using MEMS and CMOS processes. Number of remotely controlled MOMS devices including MOMS grippers, MOMS cantilevers and MOMS mirrors are presented. The performance of these devices rivals their MEMS electrostatic counterparts while consuming only fraction of energy and enabling remote controllability. Finally, the interaction of light with nanotubes for biomedical nanotechnology and photodynamic cancer therapy is presented.
Antireflection Coating for External-Cavity Quantum Cascade Laser Near 5 THz
Authors: Fenner David B. , Hensley Joel M. , Allen Mark G. , Xu Jihua , Tredicucci Alessandro
Published: April 2011

We report a simple and practical method to design and fabricate antireflection (AR) coatings for the emission facet of GaAs-based laser chips suited to operating in the very far infrared (IR) or terahertz (THz) spectral region. Vacuum-deposited silica films about 8 Ým thick serve as a single layer, quarter-wave AR and with reflectivities measured below 0.5% over ~10 cm-1 range in the far IR. Quantum cascade lasers (QCL) thus coated function well at 8-10 K coupled to a tunable, external cavity optical system at ~158 cm-1 (∼4.75 THz).
Effects of Chirality and Diameter on Electron Transport Properties in Individual Semiconducting Carbon Nanotubes
Authors: Kauser M. Zahed , Ruden P. Paul
Published: April 2011

We report on the effects of chirality and diameter on the electron transport properties in individual semiconducting, single wall carbon nanotubes. The Boltzmann transport equation is solved indirectly by the Ensemble Monte Carlo method and directly by Rode's iterative technique. Results show considerable effects of chirality and group on band structure and transport properties of tubes with small diameters. However the effects of chirality and group become negligible for tubes with large diameters. Diameter affects these properties more strongly than either chirality or group.
In Situ Synchrotron X-ray Absorption Experiments and Modelling of the Growth Rates of Electrochemically Deposited ZnO Nanostructures
Authors: Ingham Bridget , Illy Benoit N. , Mackay Jade R. , White Stephen P. , Hendy Shaun C. , Ryan Mary P.
Published: April 2011

ZnO is known to produce a wide variety of nanostructures that have enormous scope for optoelectronic applications. Using an aqueous electrochemical deposition technique, we are able to tightly control a wide range of deposition parameters (Zn2+ concentration, temperature, potential, time) and hence the resulting deposit morphology. By simultaneously conducting synchrotron x-ray absorption spectroscopy (XAS) experiments during the deposition, we are able to directly monitor the growth rates of the nanostructures, as well as providing direct chemical speciation of the films. In situ experiments such as these are critical to understanding the nucleation and growth of such nanostructures.

Recent results from in situ XAS synchrotron experiments demonstrate the growth rates as a function of potential and Zn2+ concentration. These are compared with the electrochemical current density recorded during the deposition, and the final morphology revealed through ex situ high resolution electron microscopy. The results are indicative of two distinct growth regimes, and simultaneous changes in the morphology are observed.

These experiments are complemented by modelling the growth of the rods in the transport-limited case, using the Nernst-Planck equations in 2 dimensions, to yield the growth rate of the volume, length, and radius as a function of time.
Electrodeposition of Bismuth Telluride Nanowires for Thermoelectric Applications
Authors: Scheffler Raymond H. , Ye Qi Laura , McNeil Melanie
Published: April 2011

Bismuth telluride (Bi2Te3) and its alloys have long been held as the best bulk commercial thermoelectric (TE) materials. In recent years, significant enhancement of the TE figure of merit (ZT) of these traditional TE materials has been predicted through reduction of dimensions (i.e., nanostructures and nanoengineering). We are particularly interested investigating electrolyte composition variations to control the composition of nanowires to enable large ZT enhancement. We report here the constant current electrochemical deposition of BixTey nanowires of diameters of 35, 55, 73 and 200 nm and lengths up to 50 microns. We are able to obtain controlled, uniform growth of high quality n-type bismuth telluride nanowires. A design of experimental matrix investigating the effects of current density and solution pH values on the overall growth rate and nanowire crystalline quality has been performed. The effects of growth conditions on materials and structural characteristics of BixTey nanowires have been studied by SEM, High Resolution TEM, EDX, concentric beam electron diffraction patterns, and ICP. The TE properties of individual BixTey nanowires are currently being evaluated using micro/nano fabricated devices and UHV Scanning Thermoelectric Microscopy.
Patterned Adhesion of Cells
Authors: Zimmerman Robert Lee , Gurhan Ismet , ILA Daryush
Published: April 2011

It is well known that silver deposition avoids bacterial growth and inhibits the natural process of attachment of connective tissue to biocompatible materials in vivo. We have completed a five year investigation of the precise spatial control of cell growth on glassy polymeric carbon implanted with silver using ion beam techniques, and the persistence of the inhibitory effect on cell growth. Long term inhibition of cell growth on GPC is a desirable improvement on current cardiac implants and other biocompatible materials placed in the blood stream. We have used implanted silver ions near the surface of GPC to completely inhibit cell attachment and adhesion. Cells attach and strongly adhere to areas close to the silver implanted surfaces. Patterned ion implantation permits precise control of tissue growth on GPC and other biocompatible substrates. Cell growth limited to micrometric patterns on a substrate may be useful for in vitro studies of associated biological processes in an otherwise identical environment. The patterned inhibition of cell attachment persists for periods of time significant relative to typical implant lifetimes.
Nanofabrication Based on Ion Beam-Laser Interactions with Self-Assembly of Nanoparticles
Authors: Kishimoto Naoki , Saito K. , Pan Jin , Wang H. , Takeda Y.
Published: April 2011

Ion beam-based techniques offer various possibilities for robust spatial control of nanoparticles. Since ion implantation is inherently good at depth control of solutes or nanoparticles, additional lateral control may lead to 3D control of nanoparticles. We pursue a lateral-control method of nanoparticle assembly by controlling photon-energy field under ion implantation. Laser is irradiated into a-SiO2, either sequentially or simultaneously with ion implantation. Ions of 60 keV Cu- or 3 MeV Cu2+and photons of 532 nm are used to study effects on nanoparticle evolution. Simultaneous laser irradiation under ion implantation enhances surface plasmon resonance (SPR), i.e., nanoparticle precipitation, while sequential laser irradiation of 532 nm tends to cause a decay of SPR, i.e., dissolution of Cu nanoparticles. The energy-field perturbation of laser, interactive with nanoparticle evolution, can be used for controlling nanoparticle assembly.
In-Situ Studies on Stoichiometry and Structure of Thin Film Yttria-Stabilized Zirconia under Thermal Processing
Authors: Chang C.L. , Shutthanandan V. , Singhal S. C. , Ramanathan Shriram
Published: April 2011

Thin films of 8 mol% yttria-stabilized zirconia (YSZ) of thickness ranging from 15nm-500nm have been deposited on Si3N4(90nm)/Si substrates by RF sputtering at room temperature. These samples have been studied using in situ ion scattering techniques including Rutherford backscattering spectrometry (RBS) and nuclear reaction analysis (NRA) to analyze the oxygen distribution and defect chemistry as a function of annealing in various oxidizing and reducing ambient upto 500°C. In addition, the structural quality of these films after long time annealing has been investigated using grazing incidence X-ray diffraction (GIXRD). Temperature dependent X-ray absorption spectroscopy (XAS) has been performed to study the unoccupied density of states and chemical nature of YSZ. In this paper, we will discuss in detail the effects of annealing in different ambient on the defect chemistry, structure and stability of films in these materials systems.
Doped Nanocrystalline Pt-Promoted Ceria-Zirconia as Anode Catalysts for IT SOFC: Synthesis and Properties
Authors: Sadykov Vladislav , Mezentseva Natalia , Alikina Galina , Lukashevich Anton , Muzykantov Vitalii , Bunina Rimma , Boronin Andrei , Pazhetnov Egor , Paukshtis Eugenii , Kriventsov Vladimir , Smirnova Alevtina , Vasylyev Oleksandr , Irvine John , Bobrenok Oleg , Voronin Vladimir , Berger Ivan
Published: April 2011

Ceria-zirconia samples doped with Gd, Pr, Sm, or La cations were prepared via Pechini route and promoted by Pt. Effect of their real structure and surface properties (characterized by neutronography, EXAFS, XPS, FTIRS of adsorbed CO) on the mobility and reactivity of the lattice oxygen (by oxygen isotope exchange and CH4 TPR) was analyzed. For the reaction of CH4 steam reforming (SR), catalytic performance is determined both by Pt dispersion and lattice oxygen mobility. Ni-YSZ anodes promoted by these catalysts possess a stable and efficient performance in CH4 SR in the 600-800°C range in stoichiometric feeds without coking.