bluuebunny/crossref_metadata_2025 huggingface dataset:
Mechanical Testing of Free-Standing Thin Films
Authors: Sharpe W. N. , Hemker K. J.
Published: April 2011

An overview is given of methods for testing thin-film tensile specimens of either MEMS materials or surface coatings. MEMS specimens are deposited in a final shape and need only to be released for testing, while specimens of coating materials must be extracted. Very brief descriptions of the specimen designs, force application approaches, and strain measurements are given along with a limited number of references. Representative stress-strain curves for polysilicon, silicon nitride, silicon carbide, electroplated nickel and diffusion aluminide bond coating are presented. Results at high temperatures are presented for the latter two materials.
Bonding of Bulk Piezoelectric Material to Silicon Using a Gold-Tin Eutectic Bond
Authors: Turner Kevin T. , Mlcak Richard , Roberts David C. , Spearing S. Mark
Published: April 2011

A class of MEMS devices, which utilizes microfabrication technology and bulk piezoelectric material, is currently being developed to produce high power density transducers. A thin-film gold-tin eutectic solder bond has been developed to bond electrically and mechanically bulk piezoelectric elements to microfabricated silicon structures in these devices. A 4.3 [.proportional]m thick multilayer film structure, consisting of a titanium adhesion layer, a platinum diffusion barrier, a gold-tin (80 wt.% Au - 20 wt.% Sn) alloy layer, and a pure gold capping layer, was sputter deposited on the piezoelectric components to be bonded. Bonding was accomplished by mating the piezoelectric components with silicon components metallized with a titanium-platinum-gold multilayer film and heating to approximately 300°C in a reducing atmosphere. The bonding technology allows thin, electrically conductive bonds to be formed between dissimilar materials with minimal amounts of applied pressure during bonding. Successful bonding has been achieved between single crystal silicon and polycrystalline lead-zirconate-titanate (PZT-5H) as well as between silicon and single crystal lead zinc niobate-lead titanate (PZN-PT). The process was optimized to produce mechanically robust, void-free bonds. The absence of voids was verified through scanning electron microscope examinations of bond cross-sections. Tensile tests conducted on representative structures indicated that the strength of the bond was limited by the strength of the titanium – PZT-5H interface.
Electro-Mechanical Coupling and Power Generation in a Pzt Micro-Engine
Authors: Bahr D.F. , Bruce K.R. , Olson B.W. , Eakins L.M. , Richards C.D. , Richards R.F.
Published: April 2011

A piezoelectric thin film MEMS device for generating power from a novel heat engine which approaches a Carnot cycle has been developed. The structure of the underlying electrode and PZT thin film generator has been optimized for increased adhesion. Atomic force microscopy was used to track electrode grain size and roughness; generating grain sizes of approximately 100 and 200 nm in diameter and a roughness of about 14-20 nm provide substantial improvements in film adhesion over systems with smaller grains and smoother surfaces. This has led to the ability to operate the engine at frequencies between 10 and 1500 Hz. The system of interest (a fluid filled cavity sealed by a micromachined silicon membrane and the PZT film) shows increased deflections for a given pressure applied to the membrane at frequencies where the system resonates. By operating the system dynamically, it is possible to generate more than 2 V from a single generator structure.
Ferromagnetic NiMnGa and CoNiGa Shape Memory Alloy Films
Authors: Craciunescu C. , Kishi Y. , Saraf L. , Ramesh R. , Wuttig M.
Published: April 2011

This paper reports results on Heusler-type NiMnGa and CoNiGa ferromagnetic shape memory alloy films deposited by magnetron sputtering and pulsed laser deposition respectively, on silicon cantilever-type substrates.

NiMnGa FMSMA films deposited by magnetron sputtering on silicon substrates show good ferromagnetic and shape memory properties if the substrate is heated above 350°C or if the films deposited at RT are annealed above 600°C. The growth of the film is columnar. TEM examination shows typical martensitic variants while the SAED pattern suggests an orthorhombic structure. CoNiGa FMSMA films deposited at 550°C by PLD are crystalline. Mechanical spectroscopy data proves the presence of a typical martensitic transformation that develops below room temperature: the phase transitions manifest themselves by typical changes of the modulus defect and displacement vs. temperature characteristics similar to those associated with the martensitic transformation in known shape memory alloy films.

The change in the elastic modulus as a function of the magnetic field suggests that in both NiMnGa and CoNiGa films the spontaneous magnetization is clamped by the magnetic anisotropy field.
On the Unification of Material Strength Testing for MEMS Applications
Authors: Chen Kuo-Shen
Published: April 2011

In MEMS, the geometry and applied loads between strength testing coupon and structures for design are usually different and the strength data cannot be directly applied without modification for designing brittle MEMS structures. In this paper, a method based on equal failure probability is proposed to find the equivalent strength for design by scaling the test strength with a parameter called stress ratio. By the same approach, it is also possible to correlate MEMS material strength data obtained by different testing schemes.
The Early Stages of the Microstructural Development of the Colony Structure in Bi-2223 Tapes
Authors: Holesinger T. G.
Published: April 2011

The current protocol for processing (Bi,Pb)2Sr2Ca2Cu3O10-x (Bi-2223) multifilamentary tapes involves the in situ formation of the primary phase from a suitable mixture of precursor phases. As such, the developments during the first few minutes of heat treatment determine to a large extent the efficiency of primary phase development, competing secondary phase development, texture evolution, and grain-to-grain connectivity. This work documents the development of the liquid phase, secondary phases, defects which may affect alignment and reaction kinetics, and the precipitation of Bi-2223 from the liquid phase.
High-Jc YBCO coatings on reel-to-reel dip-coated Gd2O3 seed buffer layers epitaxially fabricated on biaxially textured Ni and Ni-(3at%W-1.7at%Fe) alloy tapes
Authors: Aytug Tolga , Paranthaman M. , Sathyamurthy S. , Kang B. W. , Beach D. B. , Vallet C. E. , Specht E. D. , Lee D. F. , Feenstra R. , Goyal A. , Kroeger D. M. , Leonard K. J. , Martin P. M. , Christen D. K.
Published: April 2011

A low-cost, non-vacuum reel-to reel dip-coating system has been used to continuously fabricate epitaxial Gd2O3 buffer layers on mechanically strengthened, biaxially textured Ni- (3at.%W-1.7at%Fe), defined as Ni-alloy, metal tapes. X-ray diffraction analysis of the seed Gd2O3 layers indicated that well textured films can be obtained at processing temperatures (Tp) between 1100 and 1175°C. Processing speed did not significantly affect the crystalline quality of the Gd2O3. Scanning electron microscopy revealed a continuous, dense and crack-free surface morphology for these dip-coated buffers. The Gd2O3 layer thickness led to remarkable differences in the growth characteristics of the subsequent YSZ and CeO2 layers deposited by rfmagnetron sputtering. Epitaxial YBCO films grown by pulsed laser deposition on the short prototype CeO2/YSZ/Gd2O3/Ni-(3at%W-1.7at%Fe) conductors yielded self-field critical current densities (Jc) as high as 1.2×106 A/cm2 at 77 K. Pure Ni tapes were used to asses the viability of dip-coated buffers for long length coated conductor fabrication. The YBCO films, grown on 80 cm long and 1 cm wide CeO2/YSZ/Gd2O3 buffered Ni tapes by the industrially scalable ex-situ BaF2 precursor process, exhibited end-to-end self-field Jc of 6.25×105 A/cm2 at 77 K.
Progress towards a low-cost commercial coated conductor
Authors: Annavarapu Suresh , Nguyen Nguyet , Cui Sky , Schoop Urs , Thieme Cees , Rupich Martin W. , Kodenkandath Thomas , Verebelyi Darren , Zhang Wei , Li Xiaoping , Li Qi , Paranthaman Mariappan , Goyal Amit , Cantoni Claudia , Kowalewski Matthew M. , List Fred A.
Published: April 2011

YBCO films prepared from metal trifluoroacetate (TFA) precursors on oxide-buffered textured non-magnetic substrates have achieved performance levels equaling that on oxide buffered textured Ni substrates. Critical current densities of 0.7 MA/cm2 to 1.0 MA/cm2 have been achieved in 0.4 µm thick YBCO films on short-length of CeO2/YSZ/Y2O3/Ni/Ni-13wt%Cr substrates. High-quality epitaxial buffers comprising a Ni layer, Y2O3 seed, YSZ barrier and CeO2 cap layers have been deposited over meter long tapes of deformation textured Ni and Ni-13%Cr using reel-to-reel processes. High-performance TFA-based YBCO films have been deposited on 0.1 m to 0.3 m lengths of these oxide buffered substrates using reel to reel processes. Critical current densities up to 1.0 MA/cm2 have been achieved in 0.4 µm thick YBCO films on CeO2/YSZ/Y2O3/Ni substrates. Using multiple coats of the metal trifluoroacetate precursors, thicker YBCO films have been demonstrated on oxide buffered substrates. Critical currents in excess of 100A/cm-width have been achieved for 1.2 µm -1.6 µm thick YBCO films on short lengths of CeO2/YSZ/Y2O3/Ni substrates.
How to Optimize Critical Current Performance of RE123 Materials by Controlling Oxygen Content
Authors: Shimoyama Jun-ichi , Horii Shigeru , Otzschi Kenji , Kishio Kohji
Published: April 2011

Oxygen nonstoichiometry behaviors of REBa2Cu3Oy (RE123: RE= Nd, Sm, Eu, Gd, Dy. Ho and Y) compounds have been precisely determined by the thermogravimetric measurements. Dependence of oxygen content on temperature and oxygen partial pressure were found to slightly depend on the RE element. Thermodynamic quantities of oxygen, such as hO2 and sO2, also varied with RE element. Relationship between Tc and oxygen content is strongly dependent on the RE species. This suggests that pinnig effect due to the oxygen defects is different in each RE123 compound and, therefore, critical current properties of RE123 must be optimized by precise control of oxygen content as well as selection of suitable RE elements.
Phase Diagram Studies in the SrO-CuO-TiO2 System; Applications to YBCO Coated Conductors
Authors: Ayala A. , Holesinger T. G. , Peterson E. J. , Archuleta M.
Published: April 2011

SrTiO3 (STO) is a potential buffer layer material for use in YBa2Cu3Oy (YBCO) coated conductors based on the IBAD MgO process. However, the interactions with YBCO are not yet fully understood and little information exists in the way of phase diagrams. With this in mind, the tie-line between STO and SrCuO2 in the pseudo-ternary system SrO-CuO-TiO2 was investigated. Phase assemblages and compositions were determined by x-ray diffraction and electron microscopy in the temperature range of 1000°C to 1100°C in oxygen partial pressures of 1%, 10%, and 100%. Preliminary results showed that an appreciable amount of copper substitutes into the STO crystal structure. Conversely, Ti substitution into the SrCuO2 phase was not detected.
Thermoelectric Properties of Cd3−xAxTeO6 (A = In3+, La3+ and Bi3+) Ceramics
Authors: Luan Weiling , Shan Yue Jin , Itoh Mitsuru , Imoto Hideo
Published: April 2011

Perovskite oxide Cd3TeO6 was electron-doped by the introduction of oxygen vacancies and substitution of trivalent cations, In3+, La3+ and Bi3+. Their electric properties were investigated and compared with that of undoped Cd3TeO6. Negative temperature dependence of resistivity was observed in undoped, air-sintered Cd3TeO6. The resis tivity of Cd3−xAxTeO6 (A = In3+, La3+ and Bi3+) showed a metallic behavior with very slight temperature dependence. Indium-doped samples gave a low resistivity, which were decreased by more than three orders of magnitudes than that of air-sintered, undoped Cd3TeO6. The negative Seebeck coefficient and Hall coefficient obtained from all samples indicate that electrons are the charge carriers. The absolute Seebeck coefficients values of doped samples are decreased by 5 ∼ 10 times than that observed in undoped Cd3TeO6. Fortunately, the resistivity of indium-doped samples is low enough to provide a good thermoelectric power factor, and the optimum value of Cd2.97In0.03TeO6 was calculated as 1.35×10−4 Wm−1K−2. This result is close to that of the current best n-type perovskite thermoelectric material Ba0.4Sr0.6PbO3.
Large thermopower in metallic misfit cobalt oxides : improvement by cationic substitutions
Authors: Hébert S. , Wang L. B. , Maignan A. , Pelloquin D. , Hervieu M. , Raveau B.
Published: April 2011

The thermoelectric properties of misfit cobaltites have been investigated. Their crystallographic structure consists in the stacking of layers of tilted CoO6 edge-shared octahedra, separated by rock-salt type layers. The Tl based family was first investigated : it is shown that by increasing the Tl content, the resistivity ρ can be reduced while keeping a large thermopower S. Another way to improve the figure of merit Z=S2/(ρκ) is to partially substitute Bi for Tl to increase S and keep a small ρ. A new family of Pb-based misfits has also been investigated. Two different techniques have been attempted to decrease ρ and/or increase S in this family : the partial substitution of Cu for Co, and the partial substitution of Ca for Sr.
Thermoelectric Properties of K2Bi8−xSbxSe13Solid Solutions and Se Doping
Authors: Kyratsi Theodora , Dyck Jeffrey S. , Chen Wei , Chung Duck-Young , Uher Ctirad , Paraskevopoulos Konstantinos M. , Kanatzidis Mercouri G.
Published: April 2011

Our efforts to improve the thermoelectric properties of β-K2Bi8Se13, led to systematic studies of solid solutions of the type β-K2Bi8−xSbxSe13. The charge transport properties and thermal conductivities were studied for selected members of the series. Lattice thermal conductivity decreases due to the mass fluctuation generated in the lattice by the mixed occupation of Sb and Bi atoms. Se excess as a dopant was found to increase the figure-of merit of the solid solutions.
133Cs and 23Na NMR Studies of Cs8NaxGe136 Clathrates
Authors: Marzke R.F. , Nolas G. S. , Gryko J.
Published: April 2011

We report 133Cs and 23Na spectra of Cs8NaxGe136 clathrates. Fully loaded Cs8Na16Ge136 shows only ionic signals from both Cs and Na nuclei. In contrast to the Cs8Na16Si136 clathrate, germanium Cs8Na16Ge136 clathrate shows no large Knight or paramagnetic shifts. However, when sodium is removed from Cs8Na16Ge136, the resulting Cs8Ge136 clathrate shows a very large shift in the 133Cs NMR spectrum.
Novel Thermal Transport in Stable Binary Cd5.7Yb Quasicrystals
Authors: Pope A.L. , Tritt T.M. , Gagnon R. , Strom-Olsen J.
Published: April 2011

Quasicrystalline materials have been investigated for application as thermoelectric materials due to their inherently low thermal conductivity. With the discovery of a new stable, binary Cd5.7Yb quasicrystal, thermal and electrical transport measurements have been performed on these materials. It is found that the electronic contribution to the thermal conductivity calculated from the Wiedemann-Franz relationship is comparable to or greater than the total measured thermal conductivity, leaving the appearance of a “negligible lattice contribution.” In addition, no semblance of the lattice contribution appears in the temperature dependence of the thermal conductivity. The thermal conductivity increases linearly with temperature above 75K and proportional to T3/4 between 2 K and 75 K.
Effects of Porosity and Thermal Ageing on In-Plane Cracking Behavior of Thermal Barrier Coatings
Authors: Zhang Z. , Kameda J. , Swanson A. H. , Sakurai S. , Sato M.
Published: April 2011

This paper describes the effects of porosity and thermal ageing at 950°C for 4000 hr. in air on in-plane cracking behavior of plasma-sprayed thermal barrier coating (TBC) made up of 8 % yittria-stabilized zirconia. The in-plane TBC cracking was analyzed by a protruded TBC bend testing technique together with finite element stress analysis. As-deposited and aged TBC protruded specimens showed a large variation of porosity depending on the location of specimen extraction. The critical local tensile stress (s) necessary for the initiation of in-plane cracks for each specimen with different porosity was determined using elastic moduli (E) estimated from the porosity dependence of E. The s for in-plane cracking of the as-deposited TBC initially increased with increasing porosity and showed a peak when the porosity reached 0.23. It was shown that in-plane cracking at the interface of TBC and thermally grown oxides required much higher s than that at the interface of TBC and bond coatings. The thermal ageing led to a slight increase in s for away-from-interfacial TBC cracking. The dependence of in-plane TBC cracking behavior on the porosity is discussed in terms of effective critical stress via the Griffith criterion for porous materials.
Calcium Oxide Coating on Vanadium Alloys in Liquid Lithium
Authors: Park J.-H. , Natesan K. , Smith D. L.
Published: April 2011

We have fabricated CaO coatings on vanadium metal and various vanadium alloys (V-10Cr, V-1Ti, V-4Cr-4Ti, and V-5Cr-5Ti), for use in liquid metal blankets of fusion reactors. Initially, by monitoring weight change as a function of time, oxygen was charged into the vanadium alloys (rectangular sample, 2 x 1 x 0.1 cm) at 710°C by flowing Ar-O2gas. Oxygen-charged samples were exposed in 2.8 at.% Ca-Li at temperatures of 600 and 700°C for times between 50 and 120 h. The thickness of the in-situ-formed CaO was 13 to 30 m in the experimental conditions. Thicker CaO films were formed at higher oxygen contents and 700°C, while thinner CaO films were formed at lower oxygen contents and 600°C. The data show promise for in-situ formation of CaO layers on V alloys for the fusion blanket application.
On The Mechanism of Fatigue in Micron-Scale Structural Films of Polycrystalline Silicon
Authors: Muhlstein C. L. , Stach E. A. , Ritchie R. O.
Published: April 2011

2-μm thick structural films of polycrystalline silicon are shown to display “metal-like” stress-life fatigue behavior in room air, with failures occurring after > 1011 cycles at stresses as low as half the fracture strength. Using in situ measurements of the specimen compliance and transmission electron microscopy to characterize such damage, the mechanism of thin-film silicon fatigue is deduced to be sequential oxidation and moisture-assisted cracking in the native SiO2 layer. This mechanism can also occur in bulk silicon but it is only relevant in thin films where the critical crack size for catastrophic failure can be exceeded within the oxide layer. The fatigue susceptibility of thin-film silicon is shown to be suppressed by alkene-based self-assembled monolayer coatings that prevent the formation of the native oxide.
Physical Properties and Diffusion Characteristics of CVD-Grown TiSiN Films
Authors: Anjum Dalaver , Dovidenko Katharine , Oktyabrsky Serge , Eisenbraun Eric , Kaloyeros Alain E.
Published: April 2011

TiSiN films grown by chemical vapor deposition were characterized to evaluate the properties relevant to the application as a diffusion barrier in Cu-based interconnects. The films were grown using TiI4 + SiI4 + NH3 + H2 chemistry at substrate temperature, 370°C, and SiI4 - to-TiI4 precursor flow rate ratio of 30. The combined results from x-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM) revealed that the bulk of Ti32Si21N42 films were predominantly consisted of a mixture of cubic TiN and amorphous SiNx phases. The specific electrical resistivity of the films was about 2000 μΩcm which is a few times higher than that of sputtered TiSiN films having similar composition and thicknesses. The 40 nm-thick barrier appeared to be thermally stable against Cu diffusion at the annealing temperatures up to 550°C. Breakdown of this diffusion barrier occurred at 600°C and was accompanied by the formation of Cu3Si protrusions at the TiSiN/Si interface.
Field emission properties of nitrogen-doped diamond-like carbon films deposited by direct metal ion beam deposition
Authors: Song Kie Moon , Paik Namwoong , Kim Steven , Kim Daeil , Kim Seongjin , Kim Ju Youn , Jeon Hyeongtag
Published: April 2011

Nitrogen-doped diamond-like carbon (DLC) films were deposited on a silicon substrate by direct metal ion beam deposition (DMIBD). Partial pressures of nitrogen gas were changed to get different compositions of nitrogen in the DLC films. The composition and surface morphology of the films were examined using X-ray photoelectron spectroscopy (XPS) and atomic force microscope (AFM). Effect of nitrogen doping on field emission property was studied. The field emission data indicated that the nitrogen doping lowered the turn-on field and increase the current density. It was believed that doping of nitrogen into the DLC film plays an important role in enhancement of the field emission. This enhancement of field emission could be explained by the improvement of electron transport through nitrogen-dope DLC layer.
Investigation of Structural and Mechanical Properties of Laser Deposited Microlaminate Hard Coatings
Authors: Radder Manoj , Sikder A.K. , Kumar Ashok
Published: April 2011

Nitride and carbide are superhard material with a high potential for applications in different fields. A new group of coatings are the multilayered/microlaminate coatings, which have shown very interesting properties. Single and microlaminate films were coated on Silicon (Si) substrates using pulsed laser deposition (PLD) technique. Films were deposited at different substrate temperatures in order to study the microstructure evolution and their effect on the mechanical properties of these microlaminate films. Structure of the films was characterized by x-ray diffraction (XRD) technique. Surface morphology and roughness of the films were investigated using atomic force microscopy (AFM). Hardness and modulus of the films were investigated using nanoindentation technique. It has been demonstrated that using boron carbide as a bottom layer increases the hardness and Young's modulus values of carbide composite coatings. Microlaminates of boron carbide/titanium carbides have shown higher hardness and modulus as compared to the microlaminates of nitride coatings.
Nanoline Formation by Using Small-Aggregate Resist and Supercritical Resist Drying
Authors: Namatsu Hideo
Published: April 2011

Nanolines as small as 7 nm wide have been formed using a small-aggregate resist and supercritical resist drying. Aggregates consisting of resist polymers cause pattern roughness and cause nanolines to break. Hydrogen silsesquioxane (HSQ) is a resist material in which the aggregates are small due to its three-dimensional network. Development with an aqueous solution of TMAH provides high-contrast patterns. The problem that nanolines formed in HSQ collapse after development is solved by a supercritical resist drying technique. Supercritical drying suppresses the swelling of the resist by the rinse solution during development and thereby prevents nanolines from collapsing. The use of both small-aggregate HSQ resist and supercritical resist drying enables free-standing nanolines with a high aspect ratio to be formed without collapse.
New Photoresists with Photoacid Generator in the Backbone
Authors: Wu Hengpeng , Gonsalves Kenneth E.
Published: April 2011

A photoacid generating (PAG) sulfonium monomer was designed and synthesized. CA resists were prepared based on this PAG monomer. Incorporation of the PAG in the resist backbone offered a few advantages such as high sensitivity and absence of phase separation. These resists proved to be especially useful for low-voltage EB lithography.
Plasmon Printing – a New Approach to Near-Field Lithography
Authors: Kik Pieter G. , Maier Stefan A. , Atwater Harry A.
Published: April 2011

We propose a method for replicating patterns with a resolution well below the diffraction limit, using broad beam illumination and standard photoresist. In particular it is shown that visible exposure (λ=410 nm) of silver nanoparticles in close proximity to a thin film of g-line resist (AZ 1813) can produce selectively exposed areas with a diameter smaller than λ/20. The technique relies on the local field enhancement around metal nanostructures when illuminated at the surface plasmon resonance frequency. The method can be extended to various metals, photosensitive layers, and particle shapes.
Scanning Tunneling Microscopy Observation Of Single Dangling Bonds on the Si(100)2×1:H Surface
Authors: Liu Lequn , Yu Jixin , Lyding Joseph W.
Published: April 2011

The electrical properties of single dangling bonds on the Si(100)2×1:H surface are investigated by ultra high vacuum scanning tunneling microscopy. On the N-type Si(100)2×1:H surface, single dangling bonds created by feedback controlled lithography and natural dangling bonds have a fixed negative charge. On the other hand, they are observed as neutral on the P-type Si(100)2×1:H surface. Current image tunneling spectroscopy is used to characterize both types of dangling bonds. The dangling bonds with fixed negative charge display a dramatic voltage dependence with Friedel oscillations observed in the empty state images. The neutral dangling bonds appear as protrusions in both the empty and filled state images.
Designing Photoresist Systems for Microlithography in Carbon Dioxide
Authors: Flowers Devin , Hoggan Erik , DeSimone Joseph M. , Carbonell Ruben
Published: April 2011

Currently, the microlithography industry creates large amounts of organic and aqueous wastes in the production of semiconductors. Using carbon dioxide can possibly eliminate the majority of these waste solvents as well as eliminate the image collapse problems shown with aqueous base development. We will discuss the use of carbon dioxide to replace the most solvent intensive steps of the microlithography process, spin coating, developing, and stripping. However, before CO2 can replace conventional solvents, photoresist systems must be designed and synthesized to be compatible with CO2. These photoresist systems must be soluble in liquid CO2 to insure that thin-uniform coatings can be produced by spin coating while maintaining characteristics of conventional resist systems such as low absorbance, high sensitivity, solubility contrast, good resolution, and etch resistance. Using our CO2 compatible resist system, we will demonstrate the ability of CO2 to spin coat uniform thin-films which (after exposing and PEB) can be developed using scCO2 to produce lithography features that may be stripped in CO2. Thus, revealing the enormous potential of CO2 to provide the microlithography industry an opportunity to escape its water and organic solvent dependence as it moves toward 157nm lithography.
Influence of The Dielectric on The Growth and Performance of Pentacene Thin Film Transistors
Authors: Knipp D. , Street R. A. , Krusor B. , Ho J. , Apte R. B.
Published: April 2011

The electronic transport and the device properties of pentacene thin film transistors are reported, showing the influence of the dielectric on the structural and transport properties. The structure and morphology of pentacene films on organic and inorganic dielectrics were compared by x-ray diffraction measurements and atomic force microscopy. For the investigated dielectrics we observed a clear correlation between the morphology and the structural properties of the highly polycrystalline films. In the case of inorganic dielectrics the roughness of the dielectric has a distinct influence on the morphology and the structural properties, whereas the films on organic dielectrics bonding between pentacene and the dielectric may have an influence on the growth mechanism. We find that careful control of the deposition conditions give films with similar transport properties on organic and inorganic dielectrics. To study the electronic properties we have realized inverted staggered transistors. The TFTs exhibit mobilities of ∼0.4 cm2/Vs and on/off ratios of 108 on organic and inorganic dielectrics. The influence of the dielectric on the device mobility, threshold voltage and sub-threshold voltage slope are discussed.
Modeling of Channel Formation in Organic Field Effect Transistors
Authors: Li T. , Ruden P. P. , Campbell I. H. , Smith D. L.
Published: April 2011

We report results of two-dimensional electrostatic modeling for (top-contact) organic field effect transistors, focusing on the formation of the conductive channel. The effect on channel formation of the choice of the source and drain contact metal is investigated. High work function metal (e.g., gold) source and drain contacts produce a conducting p-type region near these contacts. In contrast, low work function metal source and drain contacts (e.g., magnesium) lead to depleted regions. In the center of the device, between the source and drain contacts, the channel carrier density at a fixed gate bias is determined by the work function of the gate contact material, and is essentially independent of the metal used to form the source and drain contacts. The dependence of the transistor threshold voltage on the gate contact metal work function and the device implications of the spatial variation of the induced charge density are discussed.
Air Stable, Amorphous Organic Films and their Applications to Solution Processable Flexible Electronics
Authors: Veres Janos , Ogier Simon , Leeming Stephen , Brown Beverley , Cupertino Domenico
Published: April 2011

The rapidly expanding field of organic semiconductors for display and low-cost electronic applications requires materials, which not only have high mobility but also benefit from solution processability and environmental stability. In this paper we present a new class of solution coatable organic materials with excellent stability to air and light. Spin-coated FET devices operate at ambient conditions without encapsulation and show p-type field-effect mobilities of 2 x 10-3 cm2V-1s-1 and on/off ratios greater than 104. Thin films can be deposited from common organic solvents onto a variety of substrates. These films are mechanically robust and can withstand temperatures in excess of 100 °C without significant changes in electrical performance. FET switching and transient characteristics at higher frequencies are also discussed. These types of materials should find applications in many areas of flexible electronics.
Investigation of Pu-Doped Ceramics Using Modified MCC-1 Leach Test
Authors: Nikolaeva Elena V. , Burakov Boris E.
Published: April 2011

Leach testing is an important tool for the investigation of chemical durability of radioactive waste forms. The data obtained from these tests allows for the selection of the most durable ceramics for the immobilization of weapons-grade plutonium. Ceramics based on cubic zirconia, (Zr,Gd,Pu)O2, doped with 10 wt.% 239Pu, zircon, (Zr,Pu)SiO4, doped with separately 5-6 and 10 wt.% 239Pu, pyrochlore, (Ca,Pu,Gd,Hf,U)2Ti2O7, doped with 10 wt.% 239Pu were studied using MCC-1 leach test. Ceramic samples were placed in test vessels with deionized water and set temperatures of 25°C and 90°C in an oven for 28 days. The leaching solution was removed and replaced with fresh deionized water after 3 and 14 days from the start of the test. Only data obtained after 14 and 28 days were used for the interpretation. No saturation of leach solution with Pu was observed in any experiments. It was found that the (without correction for porosity) normalized Pu mass loss (in g/m2 ) after 14 and 28 days was:

- for the zirconia ceramic – 2 × 10−2 to 4 × 10−2 at 90°C and 8 × 10−3 to 9 × 10−3 at 25 °C;

- for zircon doped with 5-6 wt.% of Pu – 7.0 × 10−3 to 8.2 × 10−3 at 90°C and 1.0 × 10−3 to 1.2 × 10−3 at 25 °C;

- for zircon doped with 10 wt.% of Pu – 0.2 to 0.2 at 90°C and 3.0 × 10−2 to 4.0 × 10−2 at 25 °C;

- for pyrochlore – 1.0 × 10−3 to 1.0 × 10−3 at 90°C and 2.0 × 10−3 to 3.0 × 10−3 at 25 °C.

It was shown that the high leach rate for zircon based ceramic doped with 10 wt.% Pu was caused by the presence of the separated inclusions of PuO2 phases observed in ceramic matrix. The results obtained so far allow us to conclude that ceramics based on zircon, zirconia and pyrochlore are characterized by similar chemical resistance to leaching in deionized water. Based on its low porosity, zircon may be most durable ceramic host phase for Pu.
Atomistic Simulation of Displacement Cascades in Zircon
Authors: Devanathan R. , Weber William J. , Corrales L. Rene
Published: April 2011

Low-energy displacement cascades in zircon (ZrSiO4) initiated by a Zr primary knock-on atom have been investigated by molecular dynamics (MD) simulations using a Coulombic model for long-range interactions, Buckingham potential for short-range interactions and Ziegler-Biersack potentials for close pair interactions. Displacements are found to occur mainly in the O sublattice, and O replacements by a ring mechanism are predominant. Clusters containing Si interstitials bridged by O interstitials, vacancy clusters and anti-site defects are found to occur. This Si-O-Si bridging is considerable in ZrSiO4 quenched from the melt in MD simulations.
Precipitation of Crystalline NpO2 During Oxidative Corrosion of Neptunium-Bearing Uranium Oxides
Authors: Finch Robert J.
Published: April 2011

We report crystallization of NpO2 during aqueous corrosion of unirradiated Np-bearing U3O8 under nominally oxidizing conditions. Powders of Np0.33U2.67O8 (Np:U = 1:8) were reacted in humid air at 90° and 150°c for several weeks in sealed stainless-steel vessels. Reacted solids were examined by scanning and transmission electron microscopies (SEM and TEM) and X-ray powder diffraction (XRD). Dehydrated schoepite, (UO2)O0.25–z(OH)1.5+2z (0 ≤ z ≤ 0.15), is the predominant U(VI) compound formed in these experiments and is a minor sink for Np (containing 2 wt.% Np, maximum). The primary sink for Np during corrosion of Np0.33U2.67O8 at 150°C is crystalline NpO2, which crystallized within 2 weeks of reaction in humid air. Corrosion of Np0.33U2.67O8 at 90°C resulted in crystallization of approximately equal proportions of crystalline NpO2 and Np2O5 during 16 weeks of reaction in humid air.
Nature and Effect of the Alteration Layer During Nuclear Waste Glass Dissolution
Authors: Gauthier A. , Coustumer P. Le , Thomassin J-H.
Published: April 2011

The goal of this study is to understand the role of the interface developed during R7T7 glass alteration. This glass has been leached in two different aqueous media (pure water, silica rich water and phosphorous rich water). The lixiviation tests have been optimized to assess the role of the alteration layer developed on the surface of the glass. The solution and the solid have been characterized by ICP-MS and TEM/X-EDS respectively. The results put in evidence that a complex alteration layer is formed. Its texture, structure and chemistry are discussed with respect to the evolution of the solution during the tests. The alteration layer is always present on the surface of the glass and is considered to control (at short time) diffusion of the different species through the layer. Further study must be undertaken to assess the evolution and the stability of the interface for longer time periods.
Mechanism of Vapor Phase Hydration In High-Sodium Waste Glasses from Computer Simulations
Authors: Perez-Cardenas Fernando C. , Gan Hao , Lu Xiaodong , Pegg Ian L.
Published: April 2011

The kinetics of vapor phase hydration (VHT) of high-sodium waste glasses often exhibits incubation, fast-rising, and final stages. The incubation stage is characterized by the slow and gradual appearance of transformed regions on the surface of the glass, signaling the initiation of the phase transformation. This is followed by a fast-rising stage, during which most of the transformation takes place. The final stage is characterized by the slower alteration of the remaining glass phase, which can have a duration orders of magnitude longer than those of the previous stages. While the Avrami equation provides a good representation of these features, the origin of the late-stage slow-down in the Avrami model is unrealistic for the VHT process. Computer simulations based on cell models have been used to investigate possible mechanistic origins. The models consider the formation of multiple alteration phases and simulate the complex interplay among the several microscopic mechanisms involved in the hydration process. The models assume that the transformation from the original pristine glass to the final stable altered phase occurs in two steps: from glass to a metastable phase, and then from a metastable to a stable phase. The results indicate that the late-stage slow-down can be reproduced as a result of the build-up of species that are incompatible with the stable phase or by the occlusion of the surface due to the growth of a surface phase that is less permeable to water. The simulation results are in good general agreement with the features of the experimental data.
A Glass-Encapsulated Ceramic Wasteform for the Immobilization of Chloride-Containing ILW: formation of Halite Crystals by Reaction Between the Glass Encapsulant and Ceramic Host
Authors: Donald I. W. , Metcalfe B. L. , Greedharee R. S.
Published: April 2011

We have developed a calcium phosphate ceramic based on the mineral phases chlorapatite, Ca5(PO4)3Cl, and spodiosite, Ca2(PO4)Cl, which, on the basis of evidence from non-active simulant studies, is expected to provide an extremely effective host for immobilizing the chloride constituents resulting from the pyrochemical reprocessing of Pu. The immobilized product is in the form of a free-flowing, non-hygroscopic powder in which the chlorides are chemically combined within the mineral phases. In order to provide a monolithic wasteform suitable for long term storage, the feasibility of encapsulating this product in a compatible glass is being assessed. The final wasteform will be manufactured by a pressureless sintering route with sodium aluminophosphate based glasses currently being developed for this purpose. These glasses are of particular interest due to a combination of useful properties which include good sintering characteristics, together with excellent chemical durability. We have noted, however, that during sintering the Na present in the glass reacts with the chlorapatite and spodiosite phases to form a dispersion of halite crystals within the final wasteform. The formation of free halite within the wasteform is clearly undesirable, but can be minimized by careful control over the processing parameters, in particular the sintering temperature, or by reducing the chloride loading in the wasteform. The implications of these findings are highlighted and discussed.
The Replacement of Titanium by Zirconium in Ceramics for Plutonium Immobilization
Authors: Stewart M.W.A. , Begg B.D. , Vance E.R. , Finnie K. , Li H. , Lumpkin G.R. , Smith K.L. , Weber W.J. , Thevuthasan S.
Published: April 2011

Zirconates and titanates, based on the nominal baseline composition developed for the Plutonium Immobilization Project (PIP), have been prepared with and without process impurities. The titanates form pyrochlore as the major phase and the zirconates form a defectfluorite. Little, if any, of each impurity is accommodated in the defect-fluorite and powellite, kimzeyite, a spinel and a silicate glass appear as extra phases in this ceramic. In the titanates the pyrochlore incorporates more impurities, with the remainder being accomodated in zirconolite and a small amount of silicate glass. At extremly high levels of impurities, traces of magnetoplumbite, perovskite, and loveringite were found. The defect-fluorite zirconate phase is more radiation damage resistant than the titanate pyrochlore, though the secondary phases in the zirconate will reduce the radiation damage resistance of zirconate monoliths. To produce a dense product the oxide-route zirconate required sintering temperatures of about 1550°C, 200°C higher than that required for the titanate. Silicate impurities reduce the sintering temperatures.
In Situ Isotopic Analysis of Uraninite Microstructures from the Oklo-Okélobondo Natural Fission Reactors, Gabon
Authors: Fayek Mostafa , Jensen Keld A. , Ewing Rodney C. , Riciputi Lee R.
Published: April 2011

Uranium deposits can provide important information on the long-term performance of radioactive waste forms because uraninite (UO2+X) is similar to the UO2 in spent nuclear fuel. The Oklo-Okélobondo U-deposits, Gabon, serve as natural laboratory where the long-term (hundreds to billions of years) migration of uranium and other radionuclides can be studied over large spatial scales (nm to km). The natural fission reactors associated with the Oklo- Okélobondo U-deposits occur over a range of depths (100 to 400 m) and provide a unique opportunity to study the behavior of uraninite in near surface oxidizing environments versus more reducing conditions at depth. Previously, it has been difficult to constrain the timing of interaction between U-rich minerals and post-depositional fluids. These problems are magnified because uraninite is susceptible to alteration, it continuously self-anneals radiation damage, and because these processes are manifested at the nm to μm scale. Uranium, lead and oxygen isotopes can be used to study fluid-uraninite interaction, provided that the analyses are obtained on the micro-scale. Secondary ionization mass spectrometry (SIMS) permits in situ measurement of isotopic ratios with a spatial resolution on the scale of a few μm. Preliminary U-Pb results show that uraninite from all reactor zones are highly discordant with ages aaproaching the timing of fission chain reactions (1945±50 Ma) and resetting events at 1180±47 Ma and 898±46 Ma. Oxygen isotopic analyses show that uraninite from reactors that occur in near surface environments (δ18O= −14.4‰ to −8.5‰) have reacted more extensively with groundwater of meteoric origin relative to reactors located at greater depths (μ18O= −10.2‰ to −7.3‰). This study emphasizes the importance of using in situ high spatial resolution analysis techniques for natural analogue studies.
Electrochemical detection of non-labeling DNA using electronic array
Authors: Lee H. Y. , Park J. W. , Choi Y. S. , Kannno T. , Tanaka Hiro. , Tanaka Hide. , Kawai T.
Published: April 2011

Our system is the electrochemical approaches include the detection of hybridization from nonlabeling nucleic acids to protein-bound nucleic acids using soluble mediators with K4Fe(CN)6 solutions. In order to generate bio-functional surfaces, the streptavidin(SAv)-biotin system is used. A 50 % change of redox peak current after hybridization measured with 50 μM concentration of target DNA. We suggest that this result comes from the efficient electron transport through the SAv-biotin interaction. Our electrochemical detection system showed good reproducibility on a chip with non-labeling DNA hybridization detection.
Human Spermatozoa on Nanostrucutured Ag Deposited on GaAs Surface
Authors: Quagliano Lucia G.
Published: April 2011

Motivated by the SERS (Surface Enhanced Raman Spectroscopy) sensitivity to very small amounts of material we are interested in the application of the SERS technique for studying complex biological systems, such as cells.

Using nanometer-sized Ag particles deposited on GaAs surfaces as SERS-active substrate we have observed an enhancement of Raman signal from human spermatozoa. We have obtained structural information on extremely small amounts of biomaterials and at the same time evidence that the bio-systems are preserved on the surface.

In our opinion, this kind of SERS-active substrates with nanometer-sized Ag particles on semiconductors might have promising application in nanoscale science and technology. In fact bio-molecules, cells and processes of their interfacing with Si, GaAs, silver and gold and other inorganic substrates, form the basis of bio-electronics a new emerging field at the crossing of molecular biology and nano-electronics with numerous electronic and biotechnological applications.
Control of inorganic morphologies by organic templates
Authors: Harding John H. , Duffy Dorothy M.
Published: April 2011

Experiments have shown that ordered monolayers of large organic molecules can control crystal nucleation and growth. The work of nucleation controls which morphology and phase will appear. We have used molecular dynamics to simulate the interfaces between stearic acid and a number of calcium carbonate surfaces. An important issue is the ionisation state of the acid which depends on the pH of the solution at the surface. We estimate this by solving the nonlinear Grahame equation for a calcium carbonate solution. The species in solution are chosen from geochemical models. The calculated interfacial binding energy between monolayer and material is often of the order of 1 Jm-2, suggesting that the nucleation rate is strongly enhanced.
ElectroTextiles - Technology to Applications
Authors: Ethridge Elana
Published: April 2011

ElectroTextiles is a technology area that is in its formative stages of development. Over the past three years, several government and industrial workshops as well as international conferences have discussed and presented fundamental technical approaches and a few small companies are starting to offer commercial products. The combination electronics and textiles offer a new and unique way to fabricate novel large-area, flexible and conformable military and commercial systems. This paper will discuss the some of the challenges that need to be addressed for this technology to mature in the future.
Formation of Textile Structures for Giant-Area Applications
Authors: Seyam Abdelfattah M.
Published: April 2011

Recently, textile machine manufacturers introduced to the market significant technological advances. Examples of such advances are higher speeds, higher level of automation, new concept of jacquard weaving that enables control of individual warp threads, CAD systems, and wider machines than seen before. This paper reviews the new development of formation systems of textile structures with emphasis on technologies that enables the production of giant-area fabrics. The review includes broad range of technologies (weaving, knitting, needlepunching, hydroentanglement, meltblowing, etc.). Additionally, the paper sheds the light on the potential of the textile technologies to manufacture electrotextile fabric structures.
High Speed Response of Organic Light Emitting Diodes and Photo-Detectors Fabricated on a Polymeric Substrate for Polymeric Optical Integrated Circuits
Authors: Ohmori Yutaka , Kajii Hirotake , Taneda Takayuki , Kaneko Masamitsu , Fujiki Tsubasa , Takahashi Kazuya
Published: April 2011

Organic electroluminescent diode (OELD) has been investigated for use as a light source of polymeric optical integrated devices. The OLED was fabricated by organic molecular beam deposition (OMBD) technique. The OLEDs were fabricated on both glass and polymeric substrates. The device fabricated on a polymeric substrate shows similar device characteristics to those on a glass substrate. Optical signals of faster than 100 MHz has been created by applying pulsed voltages directly to the rubrene doped OLED. Optical photo detectors (OPDs) utilizing superlattice structure phthalocyanines provide increased pulse response with input optical signals and the response was faster than 1 MHz.
Paper-Like Display Utilizing Organic Electroluminescent Diodes Fabricated on 10 Micron-Thick Polyimide Films
Authors: Ohmori Yutaka , Kajii Hirotake , Taneda Takayuki , Hikita Makoto , Takenaka Hisataka
Published: April 2011

An organic light emitting device (OLED) has been successfully fabricated on a thin paper-like polyimide substrate (about 10 μm-thick), which is sandwiched between silicone oxide and silicone nitride films. The emission characteristics of the OLEDs, which consist of diamine derivative (α-NPD) and 8-hydroxyquinoline aluminum (Alq3), are similar to those fabricated on a conventional glass substrate. Since the substrates and the OLEDs are very thin like a paper, the devices can be applicable for paper-like displays.