bluuebunny/crossref_metadata_2025 huggingface dataset:
Simfuel Leaching Studies in Granitic Groundwater Under Oxidizing Conditions
Authors: Garcia-Serrano J. , Serrano J. A. , Diaz-Arocas P. P. , Quiñones J. , Almazan J. L. R.
Published: April 2011

Simulated high-bumup nuclear fuel (SIMFUEL) has been leached in synthetic groundwater under oxic conditions. SIMFUEL pellets were ground and sieved to two particle sizes (50–100 and 100–315 μm). An extensive solid characterization of the fragments was carried out by various techniques. Elemental analysis has also been performed prior to the leaching tests.

The release of U and the minor components (Mo, Ba and Sr) was monitored during the long term dissolution experiments (350 days). These minor components exhibit a trend similar to uranium, high release at the beginning followed by a plateau. The M/U calculated ratios show different behavior although after a period of time, depending on the particle sizes, constant ratios were observed.

SIMHUEL powder was used in order to simulate the physical effect of bum-up on the fuel structure. This fact seems to play an important role on the uranium release. A comparison with the results given in the literature for SIMFUEL pellet leaching tests shows good agreement with the values reported.
Characterization of the Altered Zone Around a Fracture in Palmottu Natural Analogue
Authors: Hartikainen K. , Pietarila H. , Rasilainen K. , Nordman H. , Ruskeeniemi T. , Höltiä P. , Siitari-Kauppi M. , Timonen J.
Published: April 2011

A drill core sample penetrating at a natural fracture has been analysed by helium gas techniques and by α-autoradiography. Porosity and diffusivity profiles away from the fracture have been determined and compared with structural profiles. Model calculations are used to determine the effects of sample size on the measured porosities and diffusivities.
A Source Release Model with Application to the LANL LLRW Disposal Site Performance Assessment
Authors: Vold E. L.
Published: April 2011

A source release model was developed to quantify time dependent liquid phase releases of radioactive material to the vadose zone from a disposal site. The model has been implemented to evaluate the source terms in the Performance Assessment for the Los Alamos National Laboratory (LANL) Low Level Radioactive Waste (LLRW) Disposal Facility at Area G, an analysis of the long term post-closure impact of disposal operations required by the USDOE orders.

Analytic solutions describe transport through the model compartments: the solid phase waste package, the liquid phase within each waste package and the liquid phase within the disposal unit. The model accounts for elemental solubility limits and retardation coefficients (R) separately in the waste package and in the disposal unit. Several parameters define the site specific aspects of the disposal unit. In our case for example, the disposal unit is waste buried with crushed volcanic tuff, and a small net infiltration rate is determined from independent numerical studies. The analytic solution allows efficient explorations of the sensitivity to the input parameters. Numerical solutions extend the model to account for decay product ingrowth which may have different transport properties than the parent nuclides.

Results quantify the decrease of source release rates with package or disposal unit Kd, and the effects of solubility limits. At the LANL LLRW disposal site, thorium and uranium are the only significant contributors -to dose which are solubility limited. Otherwise, a ‘rapid rinse’ waste package category dominates the peak disposal unit efflux. This occurs for the LANL disposal site at about 100 years for nuclides with Kd= 0 (R= 1) and for proportionately longer times as Kd or R increases. Additional simple analytic models or detailed numerical codes can be coupled to these results to predict groundwater concentrations.
Effects of Aging on the Solubility of Palladium
Authors: Oda C. , Yoshikawa H. , Yui M.
Published: April 2011

Palladium solubility was measured in a dilute aqueous solution at room temperature in the pH range from 3 to 13 under anaerobic conditions. Crystalline Pd metal was clearly visible and the concentration of palladium in solution decreased gradually with aging time. The palladium concentrations in solution were less than 9.4×10-10M in the pH range from 4 to 10 and increased to 10-7M in the pH range greater than 10. This study suggests that palladium concentrations in certain high-level waste repository environments may be limited by Pd metal and may be less than 10-9M.
Uncertainty and Sensitivity Analysis of Solubility Calculations at Elevated Temperatures
Authors: Ekberg C. , Skarnemark G. , Emrén A. T. , Lundèn I.
Published: April 2011

Computer simulations are commonly used in many areas to obtain information about a system. It is, however, important to remember that the indata to these models are encumbered with errors of varying magnitude. To investigate the effect of these errors, a sensitivityuncertainty (s/u) analysis is often made.

This paper focuses on how the solubility of a solid phase is affected by uncertainties in the enthalpy of reaction for the species present in the solvent. Usually, thermodynamic data are given for a temperature of 25°C, but calculations are not made at this temperature for many practical applications. It is interesting to know which enthalpies are important and how much given uncertainties in these enthalpies affect the calculated solubility of a solid phase.

The solubility calculations were performed by the thermodynamic equilibrium program PHREEQE and the statistical evaluations with a modified version of the SENVAR program.

The solubility of e.g. UO3-2H2O at 80°C was investigated. The conclusion was that the solubility ranged from lE-05 to 4.5E-06 when the enthalpies of reaction for the interesting species were changed within a four kcal/mole wide interval. The maximum solubility, based on an arbitrary distribution, was found to be no greater than 9E-05 with 95% confidence.
Preliminary Analysis of Important Site-Specific Dose Assessment Parameters and Exposure Pathways Applicable to a Groundwater Release Scenario at Yucca Mountain
Authors: Laplante P. A. , Maheras S. J. , Jarzemba M. S.
Published: April 2011

To develop capabilities for compliance determination, the Nuclear Regulatory Commission (NRC) conducts total system performance assessment (TSPA) for the proposed repository at Yucca Mountain (YM) in an iterative manner. Because the new Environmental Protection Agency (EPA) standard for YM may set a dose or risk limit, an auxiliary study was conducted to develop estimates of site-specific dose assessment parameters for future TSPAs. YM site-relevant data was obtained for irrigation, agriculture, resuspension, crop interception, and soil. A Monte Carlo based importance analysis was used to identify predominant parameters for the groundwater pathway. In this analysis, the GENII-S code generated individual annual total effective dose equivalents (TEDEs) for 20 nuclides and 43 sampled parameters based upon unit groundwater concentrations. Scatter plots and correlation results indicate the crop interception fraction, food transfer factors, consumption rates, and irrigation rate are correlated with TEDEs for specific nuclides. Influential parameter groups correspond to expected pathway behavior of specific nuclides. Results for nuclides that transfer more readily to plants, such as 99Tc, indicate crop ingestion pathway parameters are most highly correlated with the TEDE, and those that transfer to milk (59Ni) or beef (79Se, 129I, 135Cs, 137Cs) show predominant correlations with animal product ingestion pathway parameters. Such relationships provide useful insight to important parameters and exposure pathways applicable to doses from specific nuclides.
Disposal of Aluminum Based Spent Fuels in a Repository
Authors: Louthan M. R. , Iyer N. C. , Sindelar R. L. , Peacock H. B.
Published: April 2011

Aluminum clad fuel and target elements represent approximately 10% of the DOE owned spent nuclear fuels. The uranium in a large fraction of these fuels is highly enriched and is present as uraniumaluminides which are distributed relatively uniformly within an Al-U alloy core. Emerging acceptance criteria are expected to limit the dry storage temperature for aluminum based fuels to approximately 200°C. The rock temperature near the center of a repository may exceed 200°C if the thermal loading approaches 110 kW/acre. This combination may force the placement of canisters containing aluminum based fuels near the repository periphery. The warm, moist environment anticipated at the periphery may provide aggressive conditions for corrosion of the canister and the highly enriched, aluminum based fuels. Peripheral locations may also be the most vulnerable to covert fuel removal operations. Possible consequences of mixing aluminum based fuels with other fuels in a repository are discussed in this paper.
Symmetrically Configured AC Light-Emitting (Scale) Devices: Generalizations and Variations
Authors: Wang Y. Z. , Gebler D. D. , Epstein A. J. , Wang H. L. , Swager T. M. , Macdiarmid A. G.
Published: April 2011

Most conjugated polymer-based light-emitting devices have been shown to be tunnel diodes which can only operate under forward DC driving field. Recently we have reported the fabrication of symmetrically configured AC light-emitting (SCALE) devices based on heterocyclic aromatic conjugated polymers. By adding an “insulating” layer (e.g. emeraldine base (EB) form of polyaniline) on both sides of the emitting layer, the SCALE devices emit light under both forward and reverse DC bias as well as AC driving voltage. The SCALE device structure ITO/J/emitterFl/M, has been shown to be quite general, and can be applied to a variety of electroluminescent polymers (emitter), insulating polymers (I) and electrode materials (M). Here we summarize and compare the performance of SCALE devices fabricated with different emitter, insulator, and electrode materials. The role of the insulating layer in the SCALE device operation is examined and a model that emphasizing the interface states is proposed to account for the device operation.
Molecular Beam Deposition of Organic Nonlinear Optical Materials
Authors: Schlesser R. , Dietrich T. , Sitar Z. , Günter P.
Published: April 2011

Thin films of the organic nonlinear optical materials 4‘-nitrobenzylidene-3-acetamino-4- methoxy-aniline (MNBA), and 2-cyclooctylamino-5-nitropyridine (COANP) have been deposited by organic molecular beam epitaxy. Homoepitaxial growth has been demonstrated for both materials. MNBA thin films were grown heteroepitaxially on lattice-matched ethylenediammonium terephthalate (EDT) substrates. Under optimum growth conditions, similar to those valid for homoepitaxial growth of the same material, i.e. at substrate temperatures of 80°C, and growth rates of 0.1 Å/s, highly oriented films were deposited in an island growth mode. Nonlinear optical second-harmonic generation experiments confirmed the macroscopic orientation of the deposited MNBA thin films. Growth experiments with MNBA and COANP on inorganic substrates lead to amorphous or polycrystalline films, depending primarily on the substrate temperature. A spontaneous recrystallization process, occurring in COANP thin films under ambiant conditions, led to the formation of macroscopic nonlinear optically active domain structures.
Second Harmonic Generation in Poled Polymers
Authors: Stegeman G. I. , JÄger M. , Otomo A. , Brinker W. , Yilmaz S. , Bauer S. , Horsthuis W. H. G. , MÖhlmann G. R.
Published: April 2011

The phenomenon of second harmonic generation has been studied from the earliest days of nonlinear optics.[l] To date the most impressive results in terms of conversion efficiency for as low an input power as possible have been obtained in channel waveguides made from inorganic materials.[2] However, when their second order nonlinearities (10s of pm/V) are compared with those of organic materials (10s → 100s pmn/V), it is clear that organic materials should eventually produce much better harmonic conversion efficiencies. [3]
Design of New Copolymers for Photonics Applications: Incorporation of Nlo-Active Chromophores with Well-Defined Conjugation Lengths
Authors: Spangler Charles W. , He Mingqian
Published: April 2011

Electroactive polymers such as poly [p-phenylene vinylene] (PPV) and poly [2,5-thienylene vinylene] (PTV) have been shown to yield highly conductive materials upon oxidative doping,1 and to display enhanced third order nonlinear optical response.2 Optical absorption spectra for either neutral or doped polymers, however, are quite broad, extending well into the visible for the neutral polymer and into the near infrared (NIR) for the doped polymers, with little evident fine structure. For certain nonlinear optical (NLO) applications, this can lead to undesirable absorption losses and resonance phenomena. We would like to describe how copolymers incorporating oligomeric dithienylpolyene segments may be designed so as to give some degree of control over the polymer absorption characteristics in either neutral or oxidized form.
Frenkel Biexcitons in 1D J-aggregates
Authors: Spano Frank C. , Manas Eric S.
Published: April 2011

We calculate the pump-probe spectrum of an ensemble of ID molecular aggregates, taking into account coherent exciton transport and exciton-exciton interactions. Comparison with recent experiments show that small radius biexcitons may be optically induced in PIC J-aggregates.
Epoxy Based Non-Linear Optical Polymers Functionalized With Chromophores Containing Tricyanovinyl Group
Authors: Wang Xiaogong , Chen Jeng-I , Marturunkakul Sutiyao , Li Lian , Kumar Jayant , Tripathy Sukant K.
Published: April 2011

Two types of second-order nonlinear optical epoxy-based polymers functionalized with tricyanovinyl chromophores were synthesized. One was prepared by azo coupling between an epoxy prepolymer and 4-tricyanovinylaniline while the other was synthesized by reacting the epoxy prepolymer with tetracyanoethylene. The d33 for the polymers were determined to be 243 and 178 pm/V at 1.064 μm respectively. Retentions of deff value of 83% and 65% were observed after the polymers had been heated at 80°C for 1000 hours.
Application Of Thin Films Of Conjugated Polymers In Novel Led's And Liquid Crystal “Light Valves”
Authors: Macdiarmid A. G. , Wang H. L. , Huang F. , Avlyanov J. K. , Wang P. C. , Swager T. M. , Huang Z. , Epstein A. J. , Wang Y. , Gebler D. D. , Shashidhar R. , Calvert J. M. , Crawford R. J. , Vargo T. G. , Whitesides G. M. , Xia Y. , Hsieh B. R.
Published: April 2011

Light emitting electroluminescent devices have been studied in which the conjugated light emitting polymer is separated on both sides from the device electrodes by a film of nonconducting polyaniline. The devices operate under an AC applied potential.Aluminum, copper or gold serve as the metal electrodes. Flexible, completely organic polymer dispersed liquid crystal light valves have been fabricated from transparent plastic substrates on which a conducting film of polypyrrole has been deposited. A new concept, “microcontact printing”, is being investigated for patterning the polypyrrole.
Fabrication And Characterization Of Polyimide Waveguides For Optical Interconnection
Authors: Robitaille L. , Callender C. L. , Noad J. P.
Published: April 2011

This paper reports the fabrication and characterization of polyimide branching waveguides for on-chip optical signal distribution in GaAs-based optoelectronic integrated circuits (OEICs). Low-loss polyimide s-bends and splitters with good splitting ratios and angles considerably larger than similar structures made from inorganic (e.g. LiNbO3) and semiconductor (e.g. GaAs, InP) materials, have been successfully fabricated and tested. The effects of the radius of curvature, splitter angle and cladding materials on the optical losses are discussed.
Infrared Switching Polymer Dispersed Liquid Crystals
Authors: Moody R. A. , Loh I. H. , Hed A. Z.
Published: April 2011

Infrared Polymer Dispersed Liquid Crystals (PDLCs) - polymethylmethacrylate host and E7 eutectic liquid crystal mixture - are formed through an adaptation of the thermally induced phase separation process, enabling facile creation of large liquid crystal droplet formation in the polymer host outside of the normal thermodynamic limits. The PDLCs were characterized electro-optically and microscopically. The effects of the processing parameters on the droplet morphology and switching efficiency are analyzed and presented for these systems. Droplet sizes up to 15 &m have been observed with efficient switching characteristics in the 3 - 5 μm range.
Design and synthesis of ferroelectric liquid crystals. 24. Incorporation of the disperse red 1 chromophqre into side-by-side dimers for nonlinear optics
Authors: Dyer Daniel J. , Shao Renfan , Clark Noel A. , Walba David M.
Published: April 2011

With excellent processibility on silicon integrated circuits and thermodynamically stable polar order, ferroelectric liquid crystals (FLCs) show great potential as components of fast integrated electro-optic modulators. In order to realize this potential, however, an increase in the magnitude of the electronic secona order nonlinear susceptibility χ(2) is required. This has been problematical since functional arrays with large molecular second order susceptibility β orient with improper supermolecular stereocontrol (i.e. with the charge transfer axis normal to the polar axis) when incorporated into traditional FLC structures. Herein we present examples of a new LC structural class designed to achieve the proper supermolecular structure for large χ(2) in FLCs. The observed sign and magnitude of the ferroelectric polarization of the new mesogens extrapolated from smectic C* mixtures is fully consistent with the desired supermolecular structure.
Investigations of New Self-Assembled Multilayer Thin Films Based on Alternately Adsorbed Layers of Polyelectrolytes and Functional Dye Molecules
Authors: Yoo Dongsik , Lee Jin-kyu , Rubner M. F.
Published: April 2011

The layer-by-layer self-assembly of a number of different functional dye molecules has been accomplished via the alternate spontaneous adsorption of polyelectrolytes and ionic dyes from dilute solutions. Multilayer thin films containing such functional dyes as pH indicator dyes, infrared absorbing dyes, porphyrin dyes and various fluorescent dyes have been successfully fabricated and their electrical and opt, 2al properties examined. Multilayers containing a newly synthesized ionic ruthenium based polypryidyl dye have been utilized to fabricate light emitting thin film devices with high brightness (ca. 100 cd/m2) at voltages in the range of 5–10 volts. These new light emitting thin film devices exhibit excellent stability when compared to devices based on conjugated polymers such PPV. The fabrication and device evaluation of new heterostructure thin films based on this new light emitting dye as well as the properties of other multilayer thin films containing dye molecules are presented.
Polymer Nanocomposites of Surface-Functionalized Gold
Authors: Gonsalves K. E. , Carlson G. , Kumar J. , Aranda F.
Published: April 2011

Nanometric gold particles were synthesized by a liquid/liquid phase-transfer reaction. Composites of these particles in polystyrene, poly(methyl methacrylate) and poly(phenylmethylsilane) were prepared at concentrations from 1.0 to 5.0 mg/ml were prepared, with no noticeable agglomeration of particles during processing. These materials showed a linear absorption peak at 530 nm, which is characteristic of nanosized gold. Highresolution electron microscopy measurement showed that the particle diameters were approximately 2.2 ± 1.3 nm. Degenerate four-wave mixing experiments at 532 nm yielded, on 10-micron films, a maximum value of 1.5 × 10−10 e.s.u. for the third-order nonlinear optical susceptibility.
Ladder Polymers of High Stability With Macrocyclic Metal Complexes as Subunits
Authors: Hanack M. , Hauschel B. , Stihler P. , Rack M. , Linßen T.
Published: April 2011

Macrocyclic bis-dienes and a diendienophile were prepared in Diels-Alder reactions starting from the bis-dienophilic (hemiporphyrazinato)nickel complex 1. 1 was reacted either with the tetraene 2 or with tetraphenylcyclopentadienone (4). By combination of macrocyclic bisdienes and bis-dienophiles, ladder-type oligomers were synthesized. They are precursors to the corresponding conjugated molecules, which are of interest as potential organic conductors. Monofunctional and bifunctional dienophilic macrocycles were also allowed to react with [60]fullerene to give the corresponding mono- and bis-fullerene adducts.
N-Substituted and Ring-Substituted Water Soluble Self-Aciddoped Conducting Polyanilines and their Blends with Poly(Vinyl Alcohol): Structure, Properties, and Applications
Authors: Chen Show-An , Hwang Gue-Wuu , Chuang Kuen-Ru , Shyb Shyi-Long , Loong Wen-An
Published: April 2011

The water-soluble self-acid-doped conducting polyanilines, poly(aniline-co-Npropanesulfonic acid aniline) (PAPSAH) and sulfonic acid ring substituted polyaniline (SPAN), in aqueous solutions at full concentration range are characterized. The PAPSAH and SPAN can be cast into free standing films from their aqueous solutions and have the doping level, about 0.3. Their conductivities at room temperature are about the same (10−2 S/cm). As temperature increases, conductivities of PAPSAH and SPAN increase to the maxima about 10−1 S/cm at 110°C and 190°C respectively. Above these temperatures, their conductivities drop resulting from thermal undoping accompanying with a loss of some polarons. The incorporation of PVA into PAPSAH and SPAN provides excellent flexibility and only slightly decreased conductivity (10−3 S/cm at equal weight %). Applications of these two polymers and their blends in electron beam lithography and light emitting diode are studied.
Light Emitting thin Film Devices Based on Self-assembled Multilayer Heterostructures of PPV
Authors: Ferreira M. , Onitsuka O. , Fou A. C. , Hsieh B. , Rubner M. F.
Published: April 2011

PPV based light emitting thin film devices were fabricated using a layer-by-layer deposition technique involving the alternate spontaneous adsorption of a PPV precursor polymer and either poly(styrene-4-sulfonate) (SPS) or poly(methacrylic acid) (PMA). It was demonstrated that the polyanion used to self-assemble the PPV precursor strongly influences the characteristics and performance of the resulting LEDs. Devices fabricated with PPV created in the presence of SPS exhibited symmetric I–V curves, low luminance levels and very high current densities while PPV/PMA devices exhibited luminance levels in the range of 10–60 cd/m2 and classical rectifying behavior. These dramatic differences are primarily due to a low level of p-type doping activated during the thermal conversion of PPV and/or during device operation that confers excellent hole carrier transport capabilities to the PPV/SPS combination. Fabrication of a multi-slab type heterostructure device comprised of a PPV/SPS block (hole transporting block) and a PPV/PMA block (emitting block) resulted in improved performance with luminance levels significantly higher than previously obtained for a single slab PPV/PMA device (typically > 100 cd/m2). It was also demonstrated that the presence of very thin (about 20–30 Å thick) insulating layers at the Al/polymer interface improves device efficiency by a factor of 2–4.
Synthesis of Oligomeric P-Phenyleneimine by Self-Condensation Reaction of a Novel Monomer
Authors: Afzali A. , Gelorme J. D.
Published: April 2011

A new approach for the synthesis of poly(phenylenimines) and related conjugated polymers is presented. A novel bifunctional monomer, N-Boc-indoaniline 4 is synthesized as shown in scheme I. Thermolysis of the latter, either as solid, thin film or in solution of high boiling solvents, leads to polycondensation of the bifucntional monomer and results in the formation of poly(phenyleneimine) or its reduced form. Scope and limitation of this approach in the synthesis of various poly(aryleneimines) is also described.
Poly- and Oligoaniline Thin Films: Charge Transport, Optical Properties and Effect of Doping
Authors: Paloheimo J. , Pal A. J. , Stubb H. , Granholm P. , Isotalo H.
Published: April 2011

We report a study of the electrical and optical properties of thin films of tetraanilinobenzene (TAB) and polyaniline (PANI) deposited using the Langmuir-Blodgett (LB), layer-by-layer selfassembly and vacuum-evaporation techniques. The paper will mainly concentrate on TAB LB films, but also results for other films are presented for comparison. The optical studies of undoped TAB LB films indicate H-aggregates. Upon doping new polaronic absorption bands appear and the photoluminescence of TAB becomes quenched. Doped LB and self-assembled films can reach conductivities up to about 10−4/cm for TAB and a few S/cm for PANT. The conductivity has a temperature dependence logσ α T−1/2, suggesting variable-range hopping in a quasi-gap, possibly due to the Coulomb interactions between localized carriers.
New materials for Organic Light-Emitting Diodes
Authors: Jacobs S. Joshua , Pollagi Timothy P. , Sinclair Michael B. , Scurlock Rodger D. , Ogilby Peter R.
Published: April 2011

We have investigated the performance of a class of heterocycles, 5,10-dihetera- 5,10-dihydroindeno[3,2b]indenes, as hole transport agents in simple double heterostructure organic light-emitting diodes with tris(8-hydroxyquinoline)aluminum (Alq). The best of these materials, 5,10-dihydroindolo[3,2b]indole, yields devices with luminance and lifetimes comparable to those obtained using N,N′-di-(3-methylphenyl)-N,N′- diphenyl-4,4′-diaminobiphenyl (TPD) as a hole transporting material.
Optical Tracers of Polymer Phase Transitions
Authors: Vallerio R. , Jansen S.
Published: April 2011

Phthalocyanine and quinacridone pigments have been used in a variety of photovoltaic devices [1]. These pigments find utility as photoreceptors in xerography, photoelectrochemical devices and model solar cells [2]. They are of particular interest because of their high absorption in the visible region of the electromagnetic spectrum and their inherent chemical and thermal stability [3]. Asymmetric quinacridones demonstrate significant NLO properties. In recent years, devices based on quinacridones have shown great promise. In a few of these applications thin films of quinacridones, prepared by vacuum sublimation, are deposited onto electrode materials, however, in almost all other applications, the insoluble pigment is dispersed in a polymer binder at relatively high concentration [4]. Polymeric binders include polycarbonates and polyalkylmethacrylates [5].
Processable Thiophene Copolymer With A Chiral Amino Acid Side Chain
Authors: Balasubramanian Srinivasan , Chittibabu Kethinni G. , Kumar Jayant , Tripathy Sukant K.
Published: April 2011

Conjugated polymers in general, and polythiophenes in particular have been attracting attention in the field of molecular electronics. Polythiophenes functionalized at the β- position with various groups have resulted in processable, conjugated polymeric systems with applications such as organic electrodes, photorefractive materials, electro-luminescent devices, among others. We report the synthesis of a thiophene copolymer with alkyl and chiral amino acid substituents at the β- position. We have synthesized a solution processable poly[3-octylthiophene-co-(N-1-carboxyl, 2- (4-hydroxy-3-nitrophenyl)ethyl)-3-thiophene acetamide] with 3-nitro-L-Tyrosine as the chiral amino acid side chain. The UV-Visible and optical rotatory dispersion spectra of the new copolymer are discussed.
Multilayer Structures and Emissive Regions in Organic Thin-Film Electroluminescent Diodes
Authors: Aminaka E. , Tsutsui T.
Published: April 2011

The relationships between emission quantum efficiency and emissive regions in organic thin-film electroluminescent (EL) devices were studied. As an emissive layer (EML) and an electron transport layer (ETL) material, 9, 10-bis(4-diphenylaminostyryl)anthracene and 1,3- bis(4-tert-butylphenyl-1,3,4-oxadiazolyl)phenylene, respectively, were used. A zone doped with 2,4-bis(4-diethylamino-2-hydroxyphenyl)-1,3-dihydroxycycrobutenediylium dihydroxide was formed in an EML. The relationships between the emission intensities from the dopant and the positions of doped zones gave information on the emissive regions in each EL device. The emissive region in the single-layer (SL) device consisting only of an EML extended over the EML. That in the two-layer device (DL-E) in which an EML was combined with an ETL was located within 10 nm-wide region near the EML/ETL boundary. Moreover, the emission efficiency of the DL-E device was found to be about 20 times as high as that of the SL device. Therefore, it was found that the carrier recombination within the narrow region sufficiently apart from electrodes gave high emission efficiency.
Reproducible growth of Highly Oriented (OO1) YSZ Films on Amorphous AiO2 Substrates by MOCVD
Authors: Doubinina G. , Stauf G. T.
Published: April 2011

The possibility of growing crystallographically aligned films of good quality on polycrystalline or amorphous substrates is of great interest, both for fundamental understanding of film growth mechanisms, and for potential applications such as buffer layers for silicon-on-insulator devices and an epitaxial transition layer for cuprate superconductor thin films grown on substrates with large misfits. Deposition conditions for yttria-stabilized zirconia (YSZ) thin films were investigated and optimized, and highly (001) oriented YSZ films were reproducibly prepared on amorphous substrates by MOCVD. We believe that the formation of a highly oriented crystalline film on an amorphous substrate can be interpreted in terms of the inherent features of MOCVD process, and a working model of this process is suggested.
Advanced Interactive Personal Computer-Based Process Control Systems for Oxide MOCVD Systems.
Authors: Tompa G.S. , Shen D. , Zhang C. , Murzin I.H.
Published: April 2011

A versatile control system, which uses standard commercial software and hardware has been developed and applied to control oxide (and carbide) MOCVD and CVD systems. The control system is implemented within a personal computer platform. The system operates in the real time Microsoft WindowsTM environment utilizing the full advantage of the sophisticated graphical user interfaces, dynamic data exchange, networking, and multitasking capabilities. We have used two different sets of commercial software to control and monitor system hardware. The first software set is INTOUCHTM, a Man-Machine interface software from WONDERWARETM in conjunction with Microsoft ExcelTM and I/O interface software. The second software set is LABVIEWTM, which is primarily a data acquisition control system from National Instruments, combined with Visual BasicTM. Both systems include a friendly interactive real-time windows-based user interface, an advanced process entry and recording spread sheet interface, alarm and security management systems, data display and recording, maintenance routines, and complete networking and remote operation capabilities. In addition, the configurations provide a flexible hardware interface that can directly interface to I/O cards in the PC's bus, as well as to most industrial Programmable Logic Controllers, various types of process controllers, I/O devices and other forms of hardware. Most importantly, the system can interface with any in-situ process monitor or higher level intelligent process control systems in order to optimize the process. Modules may be activated or deactivated as needed (even as part of the process). These systems have been used for home-built systems, as well as to retrofit a modified Spire SPI-MOCVDTM 500XT system. General process interaction and results will be discussed.
Preparation and Characterization Of SrTio3 Thin Films Using ECR Plasma Assisted MOCVD
Authors: Lee Joon Sung , Song Han Wook , Yoon Dae Sung , Jun Byung Hyuk , Yu Byoung Gon , Jiang Zhong Tao , Lee Won Jong , No Kwangsoo
Published: April 2011

SrTiO3 thin films were prepared on Si(p-type 100) and Pt/SiO2/Si substrates using ECR plasma (or without ECR plasma) assisted MOCVD. Sr(TMI-D)2 and Ti-isopropoxide were used as Sr and Ti metal organic sources, respectively. Perovskite SrTiO3 films were obtained at relatively low temperature of 500°C (using ECR oxygen plasma. Experimental results indicated that higher deposition temperature and ECR oxygen plasma increase the crystallinity, the dielectric constant and the leakage current density. The dielectric constant and the dielectric loss were 222 and 0.04, respectively, for 1234 Å thin SrTiO3 film (Sr/(Sr+Ti)=0.5). The leakage current density was 3.78 × 10−7 A/cm2 at 1.0V, and the dielectric breakdown field was 0.57MV/cm. SEM analyses showed that SrTiO3 films have a uniform and fine grain structure. In terms of step coverage, a lateral step coverage of 50% at 0.8 μm step (the aspect ratio was 1) was obtained with the thickness uniformity of ± 0.5% and the composition uniformity of ±1.2% at 4′′ wafer.
The Preparation and Characterization of Lithium Cobalt Oxide thin Films by LPCVD
Authors: Kenny L.T. , Breitkopf R.C. , Haas T.E. , Goldner R.B.
Published: April 2011

LPCVD thin films of lithium cobalt oxide (LiCoO2) were grown using tertbutyllithium (t-BuLi) and cyclopentadienyl cobalt dicarbonyl (CoCp(CO)2) as precursors in a cold-walled vertical reactor. Deposition rates were found to be as high as 25 A/s. Lithium to cobalt ratios (Li/Co) in the films were found to increase with increasing Ar carrier gas flow rates in the t-BuLi line while they were found to decrease with increasing system pressure. Electrochemical measurements show typical film open circuit voltages (OCV) for as-prepared films to be between 3.30 and 3.60 V vs. Li. Atomic Force Microscopy shows a striated, crystalline film formed at substrate temperatures (Ts) as low as 400 C with grain sizes as large as 200 nm in length.
Growth via Mocvd and Characterization Of GaN and AlxGa1−xN(0001) Alloys for Optoelectronic and Microelectronic Device Applications
Authors: Davis Robert F. , Weeks T. W. , Bremser M. D. , Ailey K. S. , Perry W. G.
Published: April 2011

Monocrystalline GaN(0001) thin films have been grown at 950°C on high-temperature, 100 nm thick, monocrystalline AIN(0001) buffer layers previously deposited at 1100°C on α(6H)-SiC(0001)si substrates via MOCVD in a cold-wall, vertical, pancake-style reactor. AlxGa1−xN films (0≤x≤1) were grown directly on the same SiC surface at 1100°C. Abrupt heterojunctions among the alloy composition were demonstrated. All films possessed a smooth surface morphology and were free of low-angle grain boundaries and associated oriented domain microstructures. Double-crystal x-ray rocking curve measurements for the GaN(0004) reflection for simultaneously deposited 1.4 μm films revealed FWHM values of 58 and 151 arcsec for materials grown on on-axis and off-axis material, respectively. The corresponding values for the AIN(0004) buffer layers were ≈ 200 and ≈400 arc sec, respectively. A similar relationship was found for the alloys for 0≤x≤0.2. The PL spectra of the GaN films deposited on both vicinal and on-axis substrates revealed strong bound exciton emission with a FWHM value of 4 meV. The spectra of these films on the vicinal substrates were shifted to a lower energy, indicative of films containing residual tensile stresses. A peak believed to be associated with free excitonic emission was also observed in each on-axis spectrum. Rutherford backscattering, Auger depth profiling and energy dispersive analysis were used to determine the AIN/GaN ratios in the alloys. Cathodoluminescence of solutions with x<0.5 exhibited strong near band edge emission with a FWHM as low as 31 meV. The band gaps were determined via spectral ellipsometry. Undoped GaN and A1xGa1−xN films were too resistive for accurate Hall-effect measurements. Controlled n-type Si-doping in GaN and AlxGa1−xN (for x≤0.4) was achieved for net carrier concentrations ranging from approximately 2×1017 cm−3 to 2×1019 (AlxGa1−xN) or to l × 1020 (GaN) cm−3. Mg-doped, p-type GaN was achieved with nA−nD = 3 × 1017 cm−3, p ≈ 7 Ω cm and μ ≈ 3 cm2/V·s.
MOCVD Growth Of GaxIn1−xAs1−ySby and GaxIn1−xSb ALLOYS: Effect of Growth Parameters on Their Solid Compositions
Authors: Zhang Baolin , Zhou Tianming , Jiang Hong , Ning Yongqiang , Li Shuwei , Jin Yixin
Published: April 2011

Quaternary GaxIn1−xAs1−ySby and ternary GaxIn1−xSb alloys have been grown by metalorganic chemical vapor deposition (MOCVD). The effects of growth parameters on the solid compositions, x, y for GaxIn1−xAs1−ySby and x for GaxIn1−x Sb alloys are described in detail. Concentrations of the reactants have major effects on the corresponding solid compositions in the two kinds of alloys. The growth temperature dependence of the solid compositions in both GaxIn1−xAs1−ySby and GaxIn1−xSb was obviously observed and the growth kinetic factor was considered to account for this dependence. It was found that III/V ratio in vapor has a great effect on x in GaxIn1−xSb alloy but little effect on x and y in GaxIn1−xAs1−ySby alloy.
Mocvd Routes To Thin Films For Superconducting Applications. Precursor Synthesis and Film Processing Issues
Authors: Marks T. J. , Belot J. A. , Hinds B. J. , Chen J. , Studebaker D. , Lei J. , Chang R. P. H. , Schindler J. L. , Kannewurf C. R.
Published: April 2011

Low pressure metal-organic chemical vapor deposition has been used to grow dielectric thin films of the tetragonal perovskites LaSrGaO4 and PrSrGaO4 on (110) LaAlO3 using the volatile metal sources Pr(dpm) 3, La(hfa) 3•tri, Ga(dpm) 3, and Sr(hfa) 2•tet (dpm = dipivaloylmethanate, hfa = hexafluoroacetylacetonate, tet = tetraglyme, and tri = triglyme). The PrSrGaO4, a new ternary oxide, was found to have a body-centered tetragonal lattice with a = b = 3.80 and c = 12.59 Å. Epitaxial c-axis oriented growth of these materials has been revealed by both x-ray and electron diffraction, with an average surface roughness, measured by AFM, of 1.2 nm for LaSrGaO4 and 3.0 nm for PrSrGaO4. In addition to this, the ability of these materials to function as lattice-matched buffer layers for the growth of the high temperature superconductor YBa2Cu3O7−, has been explored. The superconductive properties of the YBCO layer do not indicate any degradation attributable to the buffer layers, with the onset of superconductivity displaying a sharp metal-superconductor transition at Tc = 87.3 K and 84.5 K for the LaSrGaO4 and PrSrGaO4 systems, respectively.
Development of Novel Nickel(β-Diketonate)2.Ligand Complexes as Precursors for Mocvd of Nickel and Nickel Oxide
Authors: Spee Carel I.M.A. , Linden Hans L. , Mackor Adri , Timmer Klaas , Meinema Harry A.
Published: April 2011

Volatile and thermally stable nickel complexes have been prepared by the reaction of fluorine substituted, nickel β–diketonates with neutral (poly)oxygen and (poly)nitrogen donor ligands.

These complexes, which have low melting points, have been applied as precursors in MOCVD experiments directed on nickel and nickel oxide deposition. Investigations into the deposition of NiO in porous YSZ via particle precipitation MOCVD, for the development of an anode for a planar Solid Oxide Fuel Cell, are reported.
Modelling A Diamond Film Heatsink For GaAs Lasers
Authors: Reeves Geoffrey. K. , Shi Sanlin
Published: April 2011

Many applications for lasers require them to run at high power densities, and subsequent thermal effects can degrade their operation or limit their performance. The incorporation of a thin film of diamond in-between a laser diode and its heatsink can bring about improved laser operation through a reduction in operating temperature and temperature gradients. This paper describes the use of finite element techniques to determine the temperature distribution within a double-heterostructure laser diode and its heatsink. In the model, the diode is mounted p-side down on a copper heatsink with various thicknesses of diamond film being incorporated between the diode and the heatsink. The importance of using the correct dimensions for the diamond film are demonstrated. Various heatsink-diamond film configurations were experimentally constructed and the temperature of the active laser region measured by the nulling technique (monitoring the lasing wavelength as temperature changes). This temperature was compared to that predicted for the active region from the numerical model in order to verify the accuracy and limitations of the numerical model.
A Study of Free- and Bound-Exciton Recombination in Device Quality Diamond
Authors: Sharp S. J. , Collins A. T.
Published: April 2011

A cathodoluminescence (CL) study of free- and bound-exciton recombination in high purity high pressure high temperature (HPHT) synthetic diamond is presented, including temperature dependence measurements of the free-exciton intensity and luminescence decaytime. The results are compared with those from device quality diamond produced using the chemical vapour deposition (CVD) process.
Electronic Structure of Polycrystalline PECVD Diamond Surfaces
Authors: Humphreys T. P. , Malta D. P. , Thomas R. E. , Posthill J. B. , Mantini M. J. , Markunas R. J.
Published: April 2011

Ultraviolet and X-ray photoelectron spectroscopy techniques have been employed in a preliminary study of the electronic structure of polycrystalline diamond films that have been grown on Si substrates by if-plasma enhanced chemical vapor deposition using water/ethanol growth chemistries. In particular, polycrystalline diamond films with distinctly different surface morphologies and Raman scattering characteristics have been investigated. Corresponding ultraviolet photoemission spectra from air-exposed samples have shown the presence of a prominent low-energy secondary electron emission peak indicative of a negative electron affinity (NEA) surface. Chemical stability of the polycrystalline diamond NEA surface has been demonstrated following conventional acid cleans and hydrogen plasma processing. In contrast, an oxygen (20%)/Ar plasma exposure has been shown to extinguish the photoemission of low-energy secondary electrons and remove the NEA. However, by employing a high-temperature anneal at 750 °C for 15 min in ultra-high vacuum the NEA surface can be restored. Compared to NEA single crystal diamond surfaces the photoexcited low-energy electron emission from chemical vapor deposited polycrystalline diamond films is more robust.
Novel Technique to Produce Strongly Adherent Diamond Films on Fe- and Ni-Base Alloys
Authors: Monteiro Othon R. , Wang Zhi , Brown Ian G.
Published: April 2011

An evaluation of the use of intermediate layers for promoting adhesion between diamond and Fe and Ni base alloys is presented. The lack of adhesion between diamond and such alloys has prevented its use as a protective coating in applications at intermediate temperatures. In this study we use a combination of plasma assisted deposition techniques together with controlled bias of the substrate in order to deposit intermediate layers, and simultaneously achieve a thorough intermixing of the elements at the interface, in order to increase the adhesion between the layers. We have compared the performance of different carbide forming metals, as well as other materials. Properties considered in the selection of the appropriate intermediate layers are: chemical affinity with carbon, thermal expansion coefficient, mechanical properties, and adhesion to diamond and to the base metal as well. In the case of multiple layers, adhesion strength was measured after every new layer was deposited, in order to identify any weak links of the composite structure. Transmission electron microscopy was used to determine the microstructure and phases. An analysis is provided of the resulting performance on the basis of the microstructure.
The Control Of Intrinsic Stresses In Cvd Diamond Films With Multistep Processing
Authors: Nijhawan S. , Jankovsky S. M. , Sheldon B. W.
Published: April 2011

The role of intrinsic stresses in diamond films is examined. The films were deposited on (100) Si substrates by microwave plasma-enhanced chemical vapor deposition. The total internal stresses (thermal and intrinsic) were measured at room temperature with the bending plate method. The thermal stresses are compressive and arise due to the mismatch in thermal expansion coefficient of film and substrate. The intinsic stresses were tensile and evolved during the deposition process. These stresses increased with increasing deposition time. A 12 hour intermediate annealing treatment was found to reduce the tensile stresses considerably. The annealing treatment is most effective when the diamond crystallites are undergoing impingement and coalescence. This is consistent with the theory that the maximum tensile stresses are associated with grain boundary energetics.
Effects of Substrate Bias on the Nucleation of Diamond Films Studied by Atomic Force Microscopy
Authors: Sánchez G. , Polo M. C. , Wang W. L. , Esteve J.
Published: April 2011

The nucleation stage of diamond on silicon substrates was studied by atomic force microscopy. Samples were grown by hot filament chemical vapor deposition and substrate biases from -200 ν to +75 ν were investigated. The effects of the process on the substrate as well as on the morphology of the crystallites were observed using an atomic force microscope operating in tapping mode. It was observed that both the density and morphology of the diamond crystallites were greatly dependent on the applied bias values. The highest nucleation density was achieved for the -200 ν bias, when a plasma around the substrate holder was formed.
Mass Transport Effects In Selectively Deposited Diamond Thin Films
Authors: Kwan Michael C. , Gleason Karen K.
Published: April 2011

In order to study the effects of gas phase transport on the growth of hot-filament chemical vapor deposited (HFCVD) diamond, crystallites were selectively grown on a pre-nucleated, oxygen plasma patterned silicon wafer. Growth rate differences across the substrate were observed from scanning electron micrographs. The deposition system was then modeled with a three dimensional finite difference scheme that employed gas phase diffusion of a single growth limiting species from the hot filament to the surface coupled with a first order surface reaction. The variations in the predicted gas phase concentration directly above the surface were adjusted to match the observed growth rate differences through the Dahmk6hler number which was then used to calculate a first order surface reaction coefficient. This value was compared to published reaction coefficients for the abstraction of a surface H-atom by a gas-phase H-atom.
A Theoretical Study Of The Energetics And Vibrational Spectra Of Oxygenated (100) Diamond Surfaces
Authors: Skokov S. , Weiner B. , Frenklach M.
Published: April 2011

Static quantum ab initio and quantum semiempirical molecular dynamics calculations were employed to study reconstructions of (100) diamond surfaces in presence of hydrogen and oxygen. The results indicate that the energetically most favorable structures of oxygenated surfaces are those with chemisorbed hydroxyl groups. It was found that hydrogen bonds are formed among chemisorbed oxygenated species. The formation of these hydrogen bonds is shown to be an important factor in stabilization of adlayers. A number of important vibrational modes characteristic of oxygenated diamond surfaces were identified. The analysis of surface vibrational spectra demonstrates the influence of the local environment on the position of vibrational modes and can be useful for interpretation of experimental data.