bluuebunny/crossref_metadata_2025 huggingface dataset:
Atomic Layer Deposition of Indium Sulfide Layers for Copper Indium Gallium Diselenide Solar Cells
Authors: Donsanti F. , Weinberger B. , Cowache P. , Bernard M. C. , Lincot D.
Published: April 2011

Growth and properties of indium sulfide layers (< 300 nm) prepared by atomic layer deposition (ALD) have been studied. Growth rate of about 0.6 A per cycle has been measured for films deposited at 160°C from indium acetylacetonate and hydrogen sulfide precursors. The films are crystalline with the β modification. They possess high band gap values (2.7-2.8 eV) which are related to small grain sizes (3-4 nm) through quantum size effects. Electrical properties have been addressed using the semiconductor electrolyte junction. They are n type with a doping level around 1016 cm−3 and possess a good blocking behavior under reverse bias. The flat band potential is close to -1 V vs MSE. These figures are close to those measured under similar conditions with CdS CBD buffer layers and could explain the good cell performances obtained with ALD In2S3.
Comprehensive Study of Light-Soaking Effect in ZnO/Cu(InGa)Se2 Solar Cells with Zn-Based Buffer Layers
Authors: Chaisitsak Sutichai , Yamada Akira , Konagai Makoto
Published: April 2011

The light-soaking effect in ZnO/ Cu(InGa)Se2 (CIGS) based solar cells has been studied. A CIGS thin film with Cu(InGa)(SeS)2 surface layer was obtained by selenization (H2Se)/sulfurization (H2S). A high resistively ZnO buffer layer deposited by the atomic layer deposition technique was used as a buffer layer. We found that the light-soaking effect mainly correlates with the properties of the CIGS surface, rather than with the properties of the ZnO buffer/window layer. This phenomenon can be eliminated by surface etching or doping CIGS surface with Zinc. Zinc diffusion using diethylzinc gas has been proposed in this work. To date, we have achieved efficiency of 13.9% (Voc: 560 mV, Jsc: 35.0 mA/cm2, FF: 0.71) without light soaking effect.
Preliminary First Principles Study Of Hf and Zr Aluminates as Replacement High-k Dielectrics
Authors: Haverty Michael , Kawamoto Atsushi , Jun Gyuchang , Cho Kyeongjae , Dutton Robert
Published: April 2011

Bulk Density Functional Theory calculations were performed on Hf and Zr substitutions for Al in κ-alumina. The lowest energy configuration found was an octahedrally coordinated Zr site. Zr dissolution was favorable with an enthalpy of -2eV/unit cell for forming Al1.875Zr0.125O3 from pure Zr and κ-alumina. Hf and Zr substitution for Al atoms introduced empty d-states below the conduction band edge reducing the Eg of pure κ-alumina (7.5eV) to 6.4-5.9eV. The edge of the valence band however remained fixed by the O p-state character. The substitution of Hf and Zr into the alumina structure may lead to a higher dielectric constant, but will also reduce Eg and result in a trade off in tunneling currents in devices.
Electrical Performance and Scalability of Ni-monosilicide towards sub 0.13 μm Technologies
Authors: Lauwers Anne , de Potter Muriel , Lindsay Richard , Steegen An , Roelandts Nico , Loosen Fred , Vrancken Christa , Maex Karen
Published: April 2011

The relationship between silicide thickness, sheet resistance and silicon consumption is experimentally checked for Co-disilicide and Ni-monosilicide. The reverse bias leakage current of shallow Ni-silicided and Co-silicided square diodes is compared for varying junction depth and varying silicide thickness. A lower reverse bias leakage current is obtained for a Ni-silicided shallow junction as compared to its Co-silicided counterpart. This can be attributed to the reduced silicon consumption. The Ti cap does not play an active role during the Ni-silicidation of narrow active area and poly lines. It is shown that a Ni-silicidation process is scalable without Ti cap.
Wafer Bonding between Magnetic Garnet and Lithium Niobate for Semi-Leaky Isolator
Authors: Yokoi Hideki , Mizumoto Tetsuya , Shimizu Masafumi
Published: April 2011

A semi-leaky isolator composed of a magneto-optic / anisotropic waveguide was fabricated by wafer bonding technique. Characteristics of the semi-leaky isolator were investigated. The magneto-optic / anisotropic waveguide exhibited the semi-leaky characteristics. The isolation ratio of 7.2 dB/cm was obtained at a wavelength of 1.55 μm.
Characterization of Low Temperature Polysilicon TFTs with Self-Aligned Graded LDD Structure
Authors: Lin Ching-Wei , Cheng Li-Jing , Lu Yin-Lung , Cheng Huang-Chung
Published: April 2011

A simple process sequence for fabrication of low temperature polysilicon (LTPS) TFTs with self-aligned graded LDD structure was demonstrated. The graded LDD structure was self-aligned by side-etch of Al under the photo-resist followed by excimer laser irradiation for dopant activation and laterally diffusion. The graded LDD polysilicon TFTs were suitable for high-speed operation and active matrix switches applications because they possessed low-leakage-current characteristic without sacrificing driving capability significantly and increasing overlap capacitance. The leakage current of graded LDD polysilicon TFTs at Vd = 5V and Vg = −10V could attain to below 1pA/μm without any hygrogenation process, when proper LDD length and laser activation process were applied. The on/off current ratios of these devices were also above 108. Furthermore, due to graded dopant distribution in LDD regions, the drain electric field could be reduced further, and as a result, graded LDD polysilicon TFTs provided high reliability for high voltage operation.
Optically Assisted Metal-Induced Crystallization of Thin Si Films for Low-Cost Solar Cells
Authors: Chen Wei , Sopori Bhushan , Jones Kim , Reedy Robert , Ravindra N. M. , Aparacio Roger , Birkmire Robert , Morrison Scott , Madan Arun
Published: April 2011

Optically assisted, metal induced crystallization (MIC) was used to convert amorphous Si films, deposited on Al coated glass substrates, into polycrystalline Si (pc-Si). The study investigated the effects of deposition temperature, process temperature, and film thickness on the grain orientation, grain size, and crystallization front of the processed films. Furthermore, we have attempted to examine the role of Al in MIC – in particular, whether the metal can be confined to the interface while grain enhancement occurs.
Thin Film Metal Oxide Semiconductors Deposited on Polymeric Substrates
Authors: Fortunato Elvira , Nunes Patrícia , Marques António , Costa Daniel , ÁGuas Hugo , Ferreira Isabel , Costa Maria E. V. , Martins Rodrigo
Published: April 2011

Highly textured transparent conducting ZnO:Al thin films have been prepared by r.f. magnetron sputtering. The films were deposited on polyester (Mylar type D, 100 μm thickness) and glass substrates at room temperature. Surface stylus profiling, X-ray diffraction, scanning electron microscopy, transmission electron microscope and Hall effect measurements as a function of temperature, using the van der Pauw technique have characterized the films. The samples are polycrystalline with a hexagonal wurtzite structure and a strong crystallographic c-axis orientation (002) perpendicular to the substrate surface (columnar structure). The ZnO:Al thin films with a resistivity as low as 3.6×10−2 ωcm have been obtained, as deposited.
Polycrystalline and Amorphous Chromium Oxide MOCVD
Authors: Chang Yuneng , Huang Shengfu , Huang Minche
Published: April 2011

This paper will report the methods to deposit polycrystalline or amorphous chromium oxide (Cr2O3) thin films, which have potential applications in optoelectronics such as components for flat panel display devices. An atmospheric cold wall chemical vapor deposition (CVD) system was used to thermally decompose sublimed chromium acetylacetonate(Cr(C5H7O2)3) precursor, which gave Cr2O3 films. Oxygen concentration in gas phase is the key factor determining chromia film structure. In oxygen containing CVD system, the deposited films were polycrystalline Cr2O3, with (006), and (110) orientations. In inert, O2 free environment, the grown films were amorphous chromium oxide, as identified by XPS and XRD results. Based on depth profiling AES results, even in an oxygen free ambient, the elemental Cr/O ratio in films still remained stoichiometry(Cr:O = 2:3). Oxygen atoms might originate from acetylacetonyl (C5H7O2) ligands in the Cr(C5H7O2)3precursor.
Enhanced Low-Temperature Crystallization of Amorphous Si Films Using AlCl3 Vapor
Authors: Ahn Jin Hyung , Eom Ji Hye , Ahn Byung Tae
Published: April 2011

It is known that the direct contact between Al and a-Si enhances the crystallization of a-Si film. But the poly-Si films crystallized by the direct contact of Al metal film suffer the problems of rough surface and pores. In our study, we utilized the vapor from AlCl3 instead of Al metal film. The crystallization was enhanced by annealing a-Si films with AlCl3 that the crystallization was completed in 5h at 540. And the surface was as smooth as that of the a-Si film. The Al incorporation into the poly-Si film took place, but the content was below the detection limit of AES.
Thermal Stability of Strained Si on Relaxed Si1−xGex Buffer Layers
Authors: Mooney P.M. , Koester S.J. , Ott J.A. , Jordan-Sweet J.L. , Chu J.O. , Chan K.K.
Published: April 2011

The thermal stability of strained Si on relaxed Si1−xGex structures annealed at 1000 °C was investigated using high-resolution x-ray diffraction, Raman spectroscopy and transmission electron microscopy. Interdiffusion at the Si/Si1−xGex interface is negligible for annealing times <30 sec and is independent of the initial Si layer thickness and the composition of the Si1−xGex layer. In all cases the Si layers remained nearly fully strained, but a significant density of misfit dislocations was seen in layers that exceeded the critical thickness for dislocation glide. The Si layer thickness could be measured for layers as thin as 7 nm.
Process-Structure Relationships of Nitrided Oxides and Oxynitrides
Authors: Dasgupta Anindya , Takoudis Christos G.
Published: April 2011

The presence of nitrogen in the dielectric films is known to impart highly desirable properties in the ultra-large-scale-integration era; the position, amount and concentration profiles of nitrogen are therefore of great interest. In this work, we investigate two-step processes leading to bimodal nitrogen profiles, with one nitrogen peak near the Si/dielectric interface and the other near the dielectric surface. At 1000°C and 1 atm, a nitridation step with NH3 following either an oxidation (in O2) or oxynitridation (in N2O) step is found to result in a bimodal nitrogen concentration profile for short nitridation times. Increasing the duration of the nitridation step with NH3 is found to completely nitridate the entire film. Secondary Ion Mass, Angle Resolved X-Ray Photoelectron, and Fourier Transform Infrared Spectroscopic studies are shown to support these observations. Therefore, based on such process-property-structure relationships, the engineering of desired nitrogen concentration profiles in nano-dielectric materials of interest becomes possible. Such knowledge may have significant implications on micro- and nano-electronic applications of silicon oxynitrides.
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-νm 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.
Microfabricated Crevice Former with a Sensor Array
Authors: Wang Xiaoyan , Kelly Robert G. , Reed Michael L.
Published: April 2011

Microfabrication of crevice corrosion samples is of importance in developing an accurate, comprehensive, and reliable crevice corrosion model, and real-time acquisition of corrosion information is also essential. Solid-state microsensor arrays have been used for detecting potential, pH, and ion concentrations, and their integration into crevice corrosion testing samples will provide real-time spatial information of crevice corrosion. The crevice corrosion testing sample is constructed by coupling a crevice former to a crevice substrate and has a uniform crevice gap. In this paper we present a crevice former incorporating a potentiometric, ion- selective membrane microelectrode pH sensor array. The crevice former is built on a silicon wafer using microelectromechanical systems (MEMS) fabrication and thin film semiconductor processing techniques, and consists of an array of five independent sensing microelectrodes. The array configuration allows for in-situ spatial pH analysis of crevice corrosion based on information from each sensor. The fabrication details of the crevice former with microelectrode sensor will be elaborated.
Peak effect at microwave frequencies in swift heavy ion irradiated YBa2Cu3O7-δthin films - investigation of vortex dynamics
Authors: Banerjee Tamalika , Bhangale A. R. , Raychaudhuri P. , Kanjilal D. , Pinto R.
Published: April 2011

The vortex dynamics at microwave frequencies in YBa2Cu3O7-δ(YBCO) films has been studied. We observe a peak in the microwave surface resistance Rs vs. T (temperature) plots at 4.88 GHz in some films in magnetic fields (upto 0.8 T) whereas a few films do not show a pronounced peak in their surface resistance. This is associated with the ‘peak-effect’ phenomenon and reflects the order-disorder transformation of the flux-line lattice near the transition temperature. Introduction of artificial pinning centers like columnar defects as a result of irradiation with 200 MeV Ag ion leads to the suppression of the peak in films exhibiting the ‘peak-effect’. Interestingly, a peak is seen to develop in those films that initially did not show a peak in the surface resistance before irradiation. These results and the dynamics of the vortices at microwave frequencies for the unirradiated and irradiated films will be discussed.
AC susceptibility of the sintered Bi1.6Pb0.4Sr2(Ca1-xMx)2Cu3Oδbulk high-Tc superconductors
Authors: Adam Malik I , Shaari Abdul Halim , Hassan Zainul A , Khalid Kaida
Published: April 2011

AC susceptibility measurements as a function of temperature, frequency and applied ac field amplitude were performed on two rectangular bar shaped samples of nominal composition Bi1.6Pb0.4Sr2(Ca1-xMx)2Cu3Oδ, with M=Pr, Gd, and x=0.01, obtained by the usual solid state reaction route. The incorporation of the rare earth elements at low concentration stage results in an improvement of grain connectivity for the sample doped with Pr. On the other end, the ac field amplitude and frequency dependence of the susceptibility curves disclosed bulk pinning hystersis loss feature. The potential barrier height, activation energy at the grain boundary extracted from the low temperature peak revealed that flux creep is governing the pinning mechanism inside the samples. Qualitative discussion in the framework of the critical state model was highlighted
New conductive IBAD buffer for HTS applications
Authors: Thiele Karola , Sievers Sibylle , Dzick Juergen , Kautschor Lars-Oliver , Jooss Christian , Hoffmann Joerg , Freyhardt Herbert C.
Published: April 2011

Biaxially aligned Indium Tin Oxide (ITO) thin films to be used as electrically conductive buffer layers were prepared by an Ion-Beam Assisted Deposition (IBAD) process on various substrates. Two Kaufman ion sources with 2.5 cm diameter were employed for the assisting and the sputtering beam, respectively. All deposited films revealed (001) oriented film growth with a strong in-plane alignment. The degree of the in-plane orientation was studied depending on the ion-beam parameters and the incident angle. Investigations (TEM and X-ray) of the texture evolution of these IBAD films during film growth were carried out. An in-plane texture of 12.6°FWHM for a 1 μm thick film has been achieved so far. The quality of the buffer has been demonstrated by the subsequent deposition of high-current carrying YBCO-films deposited by thermal coevaporation using a 3–5 nm thick Y2O3 interlayer. A jc of 0.76 MA/cm2 (77K, 0T) has been obtained for a 1 cm × 1 cm sample with ITO of 20° FWHM.
Imaging Transport Current Distribution in High Temperature Superconductors Using Room Temperature Scanning Laser Microscope
Authors: Kwon C. , Klein B. E. , Seo S. , Park B. H. , Jia Q. X.
Published: April 2011

We report the feasibility of room temperature scanning laser microscopy (RTSLM) for the study of high temperature superconducing films. RTSLM images from SmBa2Cu3O7 and how that the ac–voltage response exists only in the section of the bridge where the transport current produces a voltage drop. A photolithographically defined 60 μm × 60 μm void in a 300 μm–wide bridge was clearly visible in a RTSLM image giving the spatial resolution smaller than 60 μm. In addition, the void disturbs the transport current distribution beyond itself generating an elongated shape void of 64 μm × 85 μm with the longer side along the direction of current flow in the RTSLM image. Our results indicate that the RTSLM is a useful tool to investigate the transport current distribution in high temperature superconductors.
Doping and Alloying Trends in New Thermoelectric Materials
Authors: Loo Sim , Lal Sangeeta , Kyratsi Theodora , Chung Duck-Young , Hsu Kuei-Fang , Kanatzidis Mercouri G. , Hogan Timothy P.
Published: April 2011

New thermoelectric bulk materials such as CsBi4Te6 have shown superior properties to traditional materials, however, optimal performance requires continuing investigations of doping and alloying trends. A recently modified high throughput measurement system is presented for doping and alloying investigations in several new thermoelectric materials. The modification includes a four-probe configuration for more accurate measurements while maintaining a relatively short sample preparation time. The system is fully computer controlled and provides flexible contacts to accommodate various sample dimensions. Optimal compositions are then identified for further investigations in thermoelectric prototype modules. The most promising materials will be further characterized for electrical conductivity, thermoelectric power, thermal conductivity, and Hall effect measurements as a function of temperature.
Microstructure and Thermoelectric Properties of p-Type Bi0.5Sb1.5Te3 and n-Type Bi2Te2.7Se0.3 Films Deposited by Pulsed Laser Ablation
Authors: Makala Raghuveer S. , Jagannadham K. , Sales B.C. , Wang Hsin
Published: April 2011

Thin films of p-type Bi0.5Sb1.5Te3, n-type Bi2Te2.7Se0.3 and n-type with SbI3 doping were deposited on mica substrates using Nd-YAG pulsed laser ablation at temperatures ranging from 300°C to 500°C. These films were characterized using X-ray diffraction, SEM and TEM. X-ray mapping and EDS were used to determine the composition. The films showed uniform thickness and high crystalline quality with a preferred (00n) alignment with the substrates. The film quality in terms of composition and crystal perfection is studied as a function of growth temperature. It was found that films deposited at 350°C gave improved crystallinity and thermoelectric characteristics. The Seebeck coefficient, electrical resistivity and Hall mobility were measured as a function of temperature and compared with the measurements on the bulk. Correlation of thermoelectric properties with microstructure is discussed.
Discrete State Simulation of Electrical Conductivity and the Peltier Effect for Arbitrary Band Structures
Authors: Radkowski Peter P. F. , Sands Timothy D.
Published: April 2011

An object-oriented, discrete state method for simulating coupled systems was defined. A proof-of-principle simulation of the effect of acoustic phonon scattering on electrical current was performed. Steady-state and relaxation processes were numerically simulated. A relaxation time constant was measured. The numerical simulation of Peltier cooling and heating was defined as a special case of the scattering and transport physics of the proof-of-principle simulation. The scattering terms were designed to account for local interface conditions.
Defect Formation in Boron Carbide-An ab-initio Electronic Structure Study
Authors: Wang Jun , Marshall D.S.
Published: April 2011

The electronic structure of a crystalline boron carbide has an energy forbidden gap of ∼ 3 eV and is hence a good insulator. But, on the other hand, the electrical conductivity of boron carbide is measurable. It is therefore believed that the defects formation in boron carbide is responsible for its electrical conductivity and a theory of hopping conduction of bipolaron through localized defects were developed, accordingly. Although the bipolaron electrical conductivity model does not rely on any specific type of defect, the bipolaron formation in boron carbide is believed to be a defective CBB intraicosahedral chain in connection with an B11C icosahedron. The current study examined the existing theory of bipolaron electrical conductivity by performing a systematical study on the formation energies of the defects in boron carbide using a state-of-the-art ab-initio electronic structure method. The studied defects cover a) stoichiometric variations of carbon concentration, b) missing boron atoms, and c) distribution of carbon atoms in the materials. It is found that the ground state of a fully carbonated boron carbide consists of B11C icosahedra connected by CBC intraicosahedral chains, i.e. consistent with the reported structural model of B4C. When carbon concentration is reduced, however, the population of CBC chain is found to be intact, while the population of B11C icosahedron is reduced by the replacements of B12 icosahedron. This observation is fundamentally different from the existing model of boron-rich boron carbide. The localized states associated with missing boron atoms are identified and the electrical conductivity through these localized defects states is studied.
The Microstructure and Wear Behavior of Cr- and W-DLC Coatings Sputter-Deposited onto AISI 52100 Substrates as Elucidated using Focused-Ion-Beam SEM
Authors: Cooper Clark V. , Wang Rizhi , Yoon Hyung K. , Taher Mahmoud A.
Published: April 2011

Magnetron sputtering has been used to deposit metal-containing, diamond-like-carbon (Me-DLC) coatings onto substrates composed of AISI 52100 steel in quenched-and-tempered condition. Coatings of two distinctly different compositions, one containing Was the metallic constituent and the second containing Cr, have been deposited in a plasma containing Ar and C2H2.Interrupted, unidirectional sliding experiments of the block-on-ring type have been conducted in a poly-alpha-olefin (PAO) lubricant at a load of 667 N for discrete numbers of cycles, N, of between 10 and 1000. Focused-ion-beam, scanning electron microscopy (FIB/SEM) has been applied to characterize the morphology of as-deposited and worn Me-DLC coatings. This technique has resulted in the determination that the Cr-DLC coating, deposited using the investigated processing parameters, fractures in a brittle manner through the formation and propagation of “tunnel cracks,” which unzip in a direction parallel to the grinding direction outside of the region of contact. Conversely, the application of specific processing parameters to deposit W-DLC produces a coating that wears by gradual recession, consistent with polishing wear. First-principles-based analysis shows that the state of residual stress is critically important in the behavior of the coating.
Low friction W-C:H coatings for wear resistance in roller bearings
Authors: Kacsich Thorsten , Gold Peter Werner , Loos Jörg
Published: April 2011

Life time limiting effects in roller bearings and gear wheel applications are wear, sizing, and fatigue damages like micro pitting. These mechanisms are related to a number of parameters: lubrication conditions, surface roughness, and the hardness of the bulk material. Nowadays, Me-DLC coatings like MAXITÓ W-C:H offer surface protection under dry, mixed, and hydrodynamic conditions. This allows the increase of load capacities, respectively the decrease of gearing size. Moreover, a reduction of toxic lubrication additives can be achieved. The performance of the MAXITÓ W-C:H coatings in roller bearings was investigated on the FE8 test rig under mixed friction conditions. The W-C:H was deposited via the PVD technique of magnetron sputtering onto case hardened steel. The coating thickness was varied from 1.5 to 5 m m with respect to optimised wear resistance. The wear was drastically reduced by powers of ten as compared to uncoated roller bearings.
Laser Writing of Nanostructures on Magnetic Film Surfaces With Optical Near Field Effects
Authors: Huang S. M. , Hong M. H. , Luk'yanchuk B. S. , Song W. D. , Lu Y. F. , Chong T.C.
Published: April 2011

Laser directly writing of nanostrucrures on magnetic film surfaces with optical near field effects has been investigated. Spherical 0.99 m or 0.47 m silica particles were placed on Cr/CoCrPt multilayers. After laser illumination with an excimer laser for a single shot, pits were obtained at the original position of the particles using different laser fluences or particle size parameters. The mechanism of the formation of nanostructure pattern was discussed and found to be the near-field optical resonance effect induced by particles on the surface. A comparison with accurate theoretical calculations of near-field light intensity distribution showed good agreement with the experiment results. The method of particle enhanced laser irradiation allows the study of field enhancement effects as well as its potential applications for nanolithography.
Measurement of Mechanical Properties of Single and Multilayered Nitride thin Films Prepared by Cathodic Arc Deposition
Authors: Sikder A.K. , Irfan I. M. , Kumar Ashok , Durvin Robert , McDonough Mark , Smith M. D.
Published: April 2011

Mechanical properties of thin films differ significantly from those of bulk materials due to the effects of interfaces, microstructure and thick underlying substrates. In this study we will present the results of nanoindentation tests to evaluate mechanical properties of nitride (TiN, ZrN, CrN, TiCN and TiAlN) thin films. Films were coated on steel substrates using cathodic arc deposition technique. Surface morphology and roughness of the samples are investigated using atomic force microscopy (AFM). Films were also characterized by x-ray diffraction (XRD) technique. Nanoindentation technique along with AFM and XRD methods are very useful for characterizing hard thin coatings.
Resist Requirements for Electron Projection and Direct Write Nanolithography
Authors: Ocola Leonidas E.
Published: April 2011

This paper will discuss aspects of resist properties required for nanolithography using high-energy electrons. A comprehensive image formation model is presented for positive and negative chemically amplified resists where most aspects have been considered (from exposure through development) for e-beam nanolithography (EPL, DWL). A series of optimization studies are performed using the modulation of soluble site density after PEB as a metric to characterize resist imaging performance. Base loading, blocking fraction and acid diffusion properties are investigated. Slower acid diffusion near regions with deprotected sites dominates during PEB and contributes to a sharp image modulation. Electron beam exposed nanostructures exhibit spatial fluctuations of soluble sites in the material left after development, which may alter etch resistance and pattern collapse. Soluble site fluctuations arise from the low statistics involved in the image formation and are significant contributors to the sidewall roughness.
Towards the Use of Biologically Inspired Techniques for the Assembly of Electronic Devices
Authors: McNally H. , Pingle M. , Lee S. W. , Guo D. , Bergstrom D. , Bashir R.
Published: April 2011

Nature assembles nano-scale components using molecular recognition. In the case of DNA, hydrogen bonding is the driving force behind the matching of complementary pairs of single-stranded (SS) DNA to hybridize into a double strand of helical DNA. For the case of antibodies/antigens and ligands/receptors, binding takes places by a combination of electrostatic forces, chemical bonding, and shape mediated effects. In this project, the assembly of micron sized and smaller particles using biologically inspired events such as DNA hybridization and interactions of ligands and receptors is being investigated. Following the case of DNA, a single strand sequence can be attached to the device surfaces, which is complementary to a single strand sequence previously attached to a patterned surface. Using the natural hybridization of DNA, the devices are expected to assemble in solution as designed onto the substrate surface. Single strands of DNA can be used to provide charge on the devices so that long-range electrostatic forces may be used to bring the devices close to the assembly site. We have also used a less complex molecule to add negative charges to the particles allowing them to be guided into place using electric fields. Attachment of these molecules to surfaces is a critical step in the assembly process. Various factors affecting the attachment are being investigated and will be reported. These include sample preparation and conditions for attachment. We have used polystyrene beads as test objects and optimized the capture of the beads using DNA and Avidin/Biotin interactions. When successful, this approach can be used to assemble micro and nano-scale electronic circuitry including heterogeneous integration of materials. Y6.5.1
Optical Studies of Artificial Opals as 3D Photonic Crystals
Authors: Comoretto D. , Cavallo D. , Dellepiane G. , Grassi R. , Marabelli F. , Andreani L.C. , Brabec C.J. , Andreev A. , Zakhidov A.A.
Published: April 2011

Artificial opal films have been prepared by sedimentation of monodisperse silica spheres in water suspension. Atomic force microscope images show a triangular packing of the spheres at the surface of the films. The presence and the energy position of an optical pseudo gap in incidence-angle-dependent transmittance and reflectance spectra is observed and accounted for by theoretical calculations of the photonic band structure. These calculations indicate that the pseudo gap is due to the splitting of the photonic bands in the L point of the Brillouin zone. The spectroscopic data show additional loss structures due to both other features of the Brillouin zone and the diffraction of the light from the regular surface of the sample. The effect of the infiltration of opals with polydiacetylene solutions is also reported.
Linear and cross-linked mixed conducting polycarbazoles for electrochromic devices
Authors: Tran-Van François , Vancaeyzeele Cédric , Henri Thierry , Grazulevicius Juozas V. , Chevrot Claude
Published: April 2011

A carbazole N-substituted by an oxyethylene group was polymerized using oxidative electro-polymerization. Due to the hydrophilic properties of the oligooxyethylene substituent, this monomer can be electropolymerized in aqueous solution. An acidic medium is particularly appropriate in order to decrease the oxidation potential of the monomer and to obtain films mainly composed of oligomers as revealed by SEC analysis. More particularly interesting is the stability of such material during polarization. In acidic medium 1.25 mol.L-1 HClO4, 95% of the charge density was maintained after polarization for 7000 cycles which shows the good electrochemical stability of this material compared to other polycarbazoles. Moreover, films are electroactive in aqueous electrolytes and would be well-compatible with polyethylene-oxide solid electrolytes.

In order to increase the mechanical properties of the film, we have also electropolymerized an oligomer with pendant carbazole groups obtained by acid catalyzed cationic ring opening polymerization of [N(2,3-epoxypropyl)carbazole] which leads to a new dicarbazyl cross-linked polymer with cations solvating oxyethylene segments. Due to their tridimensional structure, the mechanical strength of these films is superior to that of a linear polycarbazole film. However, their electroactivity in aqueous electrolyte is poor. So, the electropolymerization of a mixture of both monomers ensures good mechanical properties and compatibility with hydrophilic electrolyte in view to prepare an electrochromic device.
Materials Research in Nuclear Waste Management: Reflections on Twenty-Five MRS Symposia
Authors: Ewing Rodney C.
Published: April 2011

The MRS symposium, “Scientific Basis for Nuclear Waste Management” was first held in Boston, November 28th to December 1st, 1978. This symposium marks the twenty-fifth in a series that now rotate to meeting sites around the world. During the past 24 years, there has been considerable progress in the development and understanding of the behavior of materials that are used in the processing, transport, containment and disposal of radioactive waste. The design and selection of materials for long-term performance has required a uniquely interdisciplinary effort. Over the same period, there have been important developments in the regulatory framework that guides the scientific and engineering needs of nuclear waste management. This paper provides a subjective commentary on the major developments and innovations during the past 25 symposia. The future challenge will be the proper and constructive integration of the science into the development of nuclear waste disposal strategies.
Instability model of the NaZr2(PO4)3 Structure
Authors: Troole Albert , Stefanovsky Sergey
Published: April 2011

Incorporation of paramagnetic species in NaZr2(PO4)3 (NZP) single crystal made possible to investigate local distortion of the NZP structure from EPR data. Cr3+ and Fe3+ ions were used as paramagnetic probes. We mapped invariant sum of cubic component of the fourth rank tensor of crystal field, the indicative surface of the B04 element of this tensor as well as 2nd, 3rd, and 4th orders axles of the cubic component of the same tensor. From these data the coordination polyhedron of the ion-probe has been modeled and direction to charge compensator has been determined. Based on the coordination polyhedron model obtained it has been shown how would the local symmetry be lowered from C3 (initial symmetry of the Zr-polyhedron) to C1 (Zr substitute ion-probe). A comparison of dynamics of the structure occurring at lowering the symmetry with allowed dynamics of the NZP structure (Roy -Alamo-Agrawal model) makes easily explainable why the dynamics observed results in an instability of the NZP structure and breaking the symmetry from R 3c to C2/c.
A Cathodoluminescence Investigation of Pyrochlore, (Ca,Gd,Hf,U,Pu)2Ti2O7, Doped with 238Pu and 239Pu
Authors: Zamoryanskaya Maria V. , Burakov Boris E. , Bogdanov Roman V. , Sergeev Andrey S.
Published: April 2011

Crystalline ceramic based on the pyrochlore structure [(Ca,Gd,Hf,U,Pu)2Ti2O7], has been proposed in the U.S. as a candidate waste form for the immobilization of weapons grade plutonium. Several samples of synthetic polycrystalline pyrochlore doped separately with 238Pu and 239Pu were studied using cathodoluminescence (CL) and electron probe microanalysis (EPMA) immediately after synthesis and then after 175, 245 and 405 days. The CL spectra of pyrochlore doped with 239Pu and 238Pu obtained immediately after ceramic synthesis and 175 days later were nearly the same and characterized by a typical broad band emission with a maximum peak centered at 2.5 eV. New CL peaks with maximum intensities at 2.0 and 2.3 eV in the emission spectra of 238Pu-and 239Pu-doped pyrochlore were observed 245 days later. It was determined that this newly formed CL peak at 2.3 eV is similar to one in CL spectrum of artificial standard glass doped with the uranyl ion, (UO2)2+. It was suggested that CL band with maximum at 2.0 eV is caused by the U tetrahedral complex (UO4)2-. Also, the same peaks were observed in the CL spectrum of natural U-rich pyrochlore containing approximately 23 wt.% U (mainly in the form of uranyl ion). The results obtained allow us to conclude that the radiation damage of pyrochlore-based ceramic waste form is accompanied with conversion of tetravalent uranium incorporated into pyrochlore structure to the mobile uranyl ion, (UO2)2+, and complex (UO4)2-.
Experimental Determination of the Dissolution Kinetics of Plutonium- and Uranium-Bearing Ceramics at 90°C
Authors: Icenhower J. P. , McGrail B. P. , Strachan D. M. , Scheele R. D. , Legore V. L. , Rodriguez E. A. , Steele J. L. , Brown C. F. , O'Hara M. J.
Published: April 2011

As a first step toward understanding the effects of radiation damage on element release rates from Ti-bearing waste forms, we performed single-pass flow-through (SPFT) experiments with 239Pu- and 238U-bearing ceramics over a solution pH-interval of 2 to 10 at 90°C. The ceramics tested are chemically complex and are dominated volumetrically by betafite (Ti-pyrochlore) (ABTi2O7) (A = Ca2+, Gd3+, B = Gd3+, Hf4+, Pu4+, U4/6+). The 239Pu-bearing specimens contained 11.9 mass% PuO2 and 23.7 mass% UO2. In addition, a 238Pu-bearing (11.8 and 23.9 mass% PuO2 and UO2, respectively) specimen was tested at pH = 2, 90°C. The 239Pu-bearing specimens slowly released Pu to solution (rate = 7.6x10-6 g m-2 d-1), even at pH = 2. Release of elements across the pH interval investigated exhibits a weak amphoteric behavior. Compared to results from the 239Pu-bearing materials, the 238Pu-bearing specimen released Pu >1000X faster (rate = 9.3x10-3 g m-2 d-1) at pH = 2. Release rates of U, Gd, and Hf are also faster from the 238Pu-bearing ceramic compared to the specimen containing 239Pu. Although preliminary, the data can be interpreted to indicate that accumulation of radiation damage may result in faster release of Pu and U to solution than previously suspected.
Thermotransport of Hydrogen in the Modified Zircaloy-4 as a Function of Hydrogen and Oxygen Concentrations
Authors: Kim Hyun Sook , Lee Kyung Sub , Kim Seon Jin
Published: April 2011

The hydrogen redistribution induced by the thermotransport in the modified Zircaloy-4 at temperatures likely to be encountered in nuclear power reactors (300-340°C) was investigated by means of steady state techniques. The modified Zircaloy-4 was prepared by changing the chemical compositions of Zircaloy-4, which is used widely as a nuclear fuel cladding material in pressurized water reactors. The change of Q for hydrogen, which describes the direction and magnitude of the thermotransport, with increasing hydrogen and oxygen concentrations was investigated in the modified Zircaloy-4. The value of Q for hydrogen in the modified Zircloy-4 alloys was found to be about 7 kcal/mol and it was not affected by hydrogen concentration in the hydrogen concentration range from 63.3 ppm to 91.7 ppm. While the value of Q for hydrogen decreased from 6.8 kcal/mol to 4.5 kcal/mol with increasing oxygen concentration from 0.2 wt% to 1.0 wt% and it was considered to be due to the trapping of hydrogen by oxygen. In addition, the hydrogen redistribution and Q in Zircaloy-4 was also investigated in order to compare the characteristics of thermotransport of hydrogen between Zircaloy-4 and modified Zircaloy-4. The hydrogen redistribution and Q in Zircaloy-4 showed the same results to those of the modified Zircaloy-4.
Corrosion Testing of a Simulated Five-Metal Epsilon Particle in Spent Nuclear Fuel
Authors: Wronkiewicz D.J. , Watkins C.S. , Baughman A.C. , Miller F.S. , Wolf S.F.
Published: April 2011

The five-metal epsilon particle represents an important component with respect to the corrosion of spent nuclear fuel as it is the principal host for 99Tc. This radionuclide has a high solubility in oxidizing environments (as TcO4 -), a half-life of 213,000 years, and has been proposed as a monitor for the corrosion rate of spent fuel. As such, an understanding of the corrosion processes affecting epsilon particles may have important implications on our ability to accurately assess radionuclide release rates from spent nuclear fuel.

Non-radioactive metal powders were mixed in an atomic percent ratio of 40% Mo, 30% Ru, 15% Pd, 10% Re, and 5% Rh (Re used as a surrogate for Tc), a composition that simulates epsilon particles in spent reactor fuel [1,2]. The powders were electric arc-melted in the presence of an Ar-purged atmosphere. Scanning electron microscopy images of the as-cast samples denote a primary sample heterogeneity, with two distinct zones, each composed of a mixture of very fine-grained Mo-, Mo-Ru-Re, and Mo-Ru-Pd rich crystals. Results from vapor hydration tests (200°C) for time periods up to 35 days indicate the formation of Mo- and Reenriched alteration phases. Phase growth was enhanced when air was periodically replenished in the test vessels suggesting that oxide and/or hydroxide alteration phases may play a role in the corrosion process. MCC-1 tests (90°C) were conducted for time periods up to 182 days in leachant solutions that were prepared with either a) deionized water or b) deionized water acidified with nitric acid to a pH of 3.0. Solutions from the deionized water tests progressively decreased in pH with increasing reaction time (5.5 to 4.0), while the pH values remained at a near-constant value of 3.0 in the acidified solutions. Solution results indicate a preferential release of Mo followed by Re. Normalized Re/Mo release ratios varied from 0.20 to 0.86, and increased as a function of reaction time and acidity. Release of the platinum group metals (Pd, Rh, and Ru) was relatively insignificant in comparison to Mo and Re.
The Influence of Near Field Redox Conditions on Spent Fuel Leaching
Authors: Spahiu Kastriot , Eklund Ulla-Britt , Cui Daqing , Lundström Max
Published: April 2011

In a repository, the spent fuel could come in contact with groundwater if the canister or container has breached. The system may be quite complex with oxygen-free water, uranium dioxide, a corroding metal, such as iron, and a radiation field present at the same time. In an anaerobic environment iron and mild steel will corrode and hydrogen will be evolved. The equilibrium hydrogen pressure for this reaction is very high. At some time after water intrusion, there will be large amounts of dissolved hydrogen in the near field, corresponding to a partial pressure at least equivalent to the hydrostatic pressure at the repository depth. For this reason, we investigated the leaching behavior of 0.25-0.5 mm sized fragments of PWR spent fuel (43 MWd / Kg U) in simulated groundwater solution (10 mM NaCl and 2 mM HCO3-) under 5 MPa hydrogen and argon pressure. In a leaching experiment under 5 MPa hydrogen at 25 °C, the total U concentration was found to be <10−8M. After refilling of the autoclave with new solution at 70°C, the total U concentration first increased to 10−6.3M, and then quickly decreased to 10−8M. The leaching behavior of uranium and other fuel components indicates that under pressurized hydrogen, the spent fuel dissolution is substantially hindered. Leaching results obtained after the substitution of hydrogen by argon at the same pressure and temperature are also presented. Finally, some results on spent fuel leaching under pressurized argon are presented and comparatively discussed.
Ion-Induced Amorphization of Murataite
Authors: Lian Jie , Yudintsev Sergey V. , Stefanovsky Sergey V. , Kirjanova Olga I. , Ewing Rodney C.
Published: April 2011

Murataite A4B2C7O22-x, where A = Na+, Ca2+, REE3+, An3+/4+; B = Mn2+/3+, Zn2+; C = Ti4+, Fe3+, Al3+; 0≤x≤1, is an isometric, derivative of the fluorite-structure. Murataite is potentially suitable as a phase for the immobilization of rare earth (REE) and actinide elements (An). Murataite structures with three-(3C), five-(5C), and eight-fold (8C) multiples of the fluorite unit cell parameters have been identified. Radiation-induced amorphization of murataite has been investigated by 1 MeV Kr+ ion irradiation of three ceramic samples produced by melting in a resistive furnace and a cold crucible at 1400-1600 °C. The 1 MeV Kr+ ion irradiations were performed at room temperature using IVEM-Tandem Facility at Argonne National Laboratory. Radiation damage was observed by in-situ TEM. Initially, the irradiation caused disordering of the murataite structure. Murataite was rendered fully amorphous at a dose of (1.7∼1.9)Á1018 ion/m2. The pyrochlore structure phase (2C) is more radiation resistant to ion irradiation-induced amorphization than the murataite structure. Combining results on murataite with those pyrochlore and fluorite, a generally increasing trend in the susceptibility to ion beam damage is found in the fluorite-related structures as a function of the increasing multiples of the fluorite unit cells.
Total-System Performance Assessment for the Yucca Mountain Site
Authors: Wilson Michael L. , Swift Peter N. , McNeish Jerry A. , Sevougian S. David
Published: April 2011

Yucca Mountain, Nevada, is under consideration as a potential site for a repository for high-level radioactive waste. Total-system performance-assessment simulations are performed to evaluate the safety of the site. Features, events, and processes have been systematically evaluated to determine which ones are significant to the safety assessment. Computer models of the disposal system have been developed within a probabilistic framework, including both engineered and natural components. Selected results are presented for three different total-system simulations, and the behavior of the disposal system is discussed. The results show that risk is dominated by igneous activity at early times, because the robust waste-package design prevents significant nominal (non-disruptive) releases for tens of thousands of years or longer. The uncertainty in the nominal performance is dominated by uncertainties related to waste-package corrosion at early times and by uncertainties in the natural system, most significantly infiltration, at late times.
Dissolution of A2Ti2O7 (A = Y3+, Gd3+, or Lu3+) Pyrochlore by Experiment at pH = 2, T = 90°C: Evidence for Solubility Control Using a Linear Free Energy Model
Authors: Icenhower J. P. , McGrail B. P. , Weber W. J. , Begg B. D. , Hess N. J. , Rodriguez E. A. , Steele J. L. , Brown C. F. , O'Hara and M. J.
Published: April 2011

We performed a series of dissolution experiments with well-characterized pyrochlore ceramics with the formula A2Ti2O7, where A = Y3+, Gd3+, or Lu3+ in H2O- and D2Obased solutions [pH(D) = 2] at 90°C. Normalized log10 dissolution rates (g·m−2·d−1) in H2O-based solutions increase from Lu2Ti2O7 (−3.2 to –3.3) to Gd2Ti2O7 (−2.6 to –2.9), to Y2Ti2O7 (−1.9 to –2.0). Rates in D20-based solutions are indistinguishable from rates in H2O, indicating that release of elements is probably not diffusion controlled. A recent dissolution model, based on ligand-exchange reactions, suggests that the rate of reaction should increase in inverse order of the cation field strength: Lu < Y < Gd (where the cation denotes the appropriate pyrochlore composition), which is not observed. Evaluation of the thermodynamic stability of the three solids was performed using a linear free-energy model and reported free energies of formation. The calculations indicate that reactivity should follow in the progression Lu < Gd < Y, as observed in the dissolution experiments. Our data indicates, therefore, that dissolution models based on ligand-exchange reactions may not be strictly applicable to simple pyrochlore minerals.