bluuebunny/crossref_metadata_2025 huggingface dataset:
Unmet therapeutic, educational and scientific needs in parathyroid disorders: Consensus Statement from the first European Society of Endocrinology Workshop (PARAT)
Authors: Bollerslev Jens , Schalin-Jäntti Camilla , Rejnmark Lars , Siggelkow Heide , Morreau Hans , Thakker Rajesh , Sitges-Serra Antonio , Cetani Filomena , Marcocci Claudio , _ _ , _ _ , Guistina Andrea , Van Hul Wim , Amrein Karin , Sikjaer Tanja , Hindie Elif , Vamvakidis Kyriakos , Corbetta Sabrina , Balaia Zhanna , Astor Marianne , Makay Ozer , Newey Paul , Hannan Fadil , Rolighed Lars , Appelman-Dijkstra Natasha , Wicke Corrina , Pilz Stefan , Saponaro Federica , Vestergard Peter
Published: June 2019

PARAT, a new European Society of Endocrinology program, aims to identify unmet scientific and educational needs of parathyroid disorders, such as primary hyperparathyroidism (PHPT), including parathyroid cancer (PC), and hypoparathyroidism (HypoPT). The discussions and consensus statements from the first PARAT workshop (September 2018) are reviewed. PHPT has a high prevalence in Western communities, yet evidence is sparse concerning the natural history and whether morbidity and long-term outcomes are related to hypercalcemia or plasma PTH concentrations or both. Cardiovascular mortality and prevalence of low energy fractures are increased, whereas quality of life is decreased, although their reversibility by treatment of PHPT has not been convincingly demonstrated. PC is a rare cause of PHPT, with increasing incidence, and international collaborative studies are required to advance knowledge of the genetic mechanisms, biomarkers for disease activity and optimal treatments. For example, ~20% of PCs demonstrate high mutational burden, and identifying targetable DNA variations, gene amplifications and gene fusions may facilitate personalized care, such as different forms of immunotherapy or targeted therapy. HypoPT, a designated orphan disease, is associated with a high risk of symptoms and complications. Most cases are secondary to neck surgery. However, there is a need to better understand the relation between disease biomarkers and intellectual function and to establish the role of PTH in target tissues, as these may facilitate the appropriate use of PTH substitution therapy. Management of parathyroid disorders is challenging, and PARAT has highlighted the need for international transdisciplinary scientific and educational studies in advancing in this field.
The Evolutionary Dynamics of a Genetic Barrier to Gene Flow: From the Establishment to the Emergence of a Peak of Divergence
Authors: Sakamoto Takahiro , Innan Hideki
Published: June 2019

Divergent selection works when an allele establishes in the subpopulations in which it is adaptive, but not in the ones in which it is deleterious. While such a locally adaptive allele is maintained, the target locus of selection works as a genetic barrier to gene flow or a barrier locus. The genetic divergence (or FST) around the barrier locus can be maintained, while in other regions of the genome, genetic variation can be mixed by gene flow or migration. In this work, we consider theoretically the evolutionary process of a barrier locus, from its birth to stable preservation. Under a simple two-population model, we use a diffusion approach to obtain analytical expressions for the probability of initial establishment of a locally adaptive allele, the reduction of genetic variation due to the spread of the adaptive allele, and the process to the development of a sharp peak of divergence (genomic island of divergence). Our results will be useful to understanding how genomes evolve through local adaptation and divergent selection.
Three new records of lichenised fungi from India
Authors: Haq Manzoor Ul , Reshi Zafar A. , Kumar Upreti Dalip
Published: June 2019

Three lichen species, namely Amandinea errata and Baculifera xylophila, belonging to family Caliciaceae, and Baeomyces rufus, of family Baeomycetaceae, are newly reported for the Indian lichen biota. A brief morphotaxonomic description of each species, along with their ecology and distribution, is also provided.
Si nanowire-gold nanoparticles heterostructures for surface enhanced Raman spectroscopy
Authors: Li Yuan , Dykes John C. , Chopra Nitin
Published: June 2019

Here, we present a method for the fabrication of silicon (Si) nanowires and Si nanowire-gold nanoparticles (AuNPs) heterostructures for surface-enhanced Raman scattering (SERS) effect. Branched Si nanowires were grown in atmospheric pressure chemical vapor deposition (CVD) process. Further decoration of these nanowires was achieved by a galvanic deposition of gold followed by annealing procedure. This resulted in Si nanowires-AuNPs heterostructures with controlled size and inter-particle spacing. Furthermore, the fabricated heterostructures were studied for Raman signal enhancement of the low concentration (∼10-6 M) dye (Rhodamine 6G, R6G). It was observed that heterostructuring of SiNWs with AuNPs led to improvement of R6G signals as compared to AuNPs dispersed on flat Si substrate.
Amorphous Silicon Laser Quenched from the Melt - Preparation & Characterization
Authors: Cullis A.G. , Webber H.C. , Chew N.G.
Published: June 2019

Short (2.5nsec) pulses of ultra-violet radiation from a Q-switched laser system have been used to induce a range of defect transitions in the surface regions of (001) and (111) Si single crystal by transient melting and resolidification. Relatively large areas of Si have been uniformly processed and this has enabled the measurement of thresholds for both amorphization and extended defect production. The highest quench rates (isotherm velocities of ∼20m/sec) were achieved at the surface melting threshold near 0.2J/cm2 and both (001) and (111) Si could be amorphized with radiation energy densities close to this value. With increasing energy density the quench rate fell and (001) Si ceased to amorphize before (111) Si. Furthermore, over a range of high radiation fluxes the crystalline Si produced on (111) surfaces was highly defective and contained twins due to errors in liquid-phase epitaxy. The various observed structure transitions have been related to the predictions of crystal growth theory with account taken of melt undercooling effects. The amorphous Si produced during this work (up to almost 1000Å thickness) has been shown to be structurally similar to that produced by conventional methods. Both direct analysis and solid-phase regrowth experiments have demonstrated that its impurity content is negligible.
Dynamic Behavior of Nano Second Pulsed Nd:Glass Laser Annealing in Ion Implanted Silicon
Authors: Takai M. , Sato Y. , Murakami K. , Gamo K. , Minamisono T. , Namba S.
Published: June 2019

Time resolved transmission (λ = 1060 nm) and reflectivity (λ = 632.8 nm) during 20 nsec Nd:glass laser annealing in ion implanted Si were measured to study dynamic behaviors of laser annealing. Transmitted laser energy was also measured to complement transient measurements. Transient transmitted light intensity was found to be almost completely quenched as would be expected from absorption by a molten Si layer.
Ultrasound Studies of Clathrate Thermoelectrics
Authors: Keppens Veerle , Sales Brian. C. , Mandrus David , Chakoumakos Bryan C. , Laermans Christiane
Published: June 2019

Resonant Ultrasound Spectroscopy and low-temperature ultrasonic attenuation measurements are reported for filled and unfilled skutterudites and for Ge-clathrates. These data reveal that an unusual elastic behavior complements the thermal properties of the filled skutterudites and indicate the presence of low-energy vibrational modes. The attenuation at low-temperatures in the single-crystalline Ge-clathrate is glasslike and can be described by the same phenomenological Tunneling Model that has been developed to describe the low-temperature properties of amorphous solids.
Experimental Investigation of Thin Film InGaAsP Coolers
Authors: LaBounty Christopher J. , Shakouri Ali , Robinson Gerry , Esparza Luis , Abraham Patrick , Bowers John E.
Published: June 2019

Most optoelectronic devices for long haul optical communications are based on the InP/InGaAsP family of materials. Thin film coolers based on the same material system can be monolithically integrated with optoelectronic devices such as lasers, switches, and photodetectors to control precisely the device characteristics such as wavelength and optical power. Superlattice structures of InGaAs/InP and InGaAs/InGaAsP are used to optimize the thermionic emission resulting in a cooling behavior beyond what is possible with only the Peltier effect. A careful experimental study of these coolers is undertaken. Mesa sizes, superlattice thickness, and ambient temperature are all varied to determine their effect on cooling performance. A three-dimensional, self-consistent thermal-electric simulation and an effective one-dimensional model are used to understand the experimental observations and to predict what will occur for other untested parameters. The packaging of the coolers is also determined to have consequences in the overall device performance. Cooling on the order of 1 to 2.3 degrees over 1-micron thick barriers is reported.
Connections between Crystallographic Data and New Thermoelectric Compounds
Authors: Sales B. C. , Chakoumakos B. C. , Mandrus D.
Published: June 2019

New bulk thermoelectric compounds are normally discovered with the aid of simple qualitative structure-property relationships. Most good thermoelectric materials are narrow gap semiconductors composed of heavy elements with similar electronegativities. The crystal structures are usually of high symmetry (cubic, hexagonal, and possibly tetragonal), and often contain a large number of atoms per unit cell. In the present work a new structure-property relationship is discussed which links atomic displacement parameters (ADPs) and the lattice thermal conductivity of clathrate-like compounds. For many clathrate-like compounds, in which one of the atom-types is weakly bound and “rattles” within its atomic cage, room temperature ADP information can be used to estimate the room temperature lattice thermal conductivity, the vibration frequency of the “rattler”, and the temperature dependence of the heat capacity. ADPs are reported as part of the crystal structure description, and hence APDs represent some of the first information that is known about a new compound. For most ternary and quaternary compounds, all that is known is its crystal structure. ADP information thus provides a useful screening tool for the large and growing crystallographic databases. Examples of the use and limitations of this analysis are presented for several promising classes of thermoelectric materials.
High-Z Lanthanum-Cerium Hexaborate Thin Films for Low-Temperature Applications
Authors: Kuzanyan Armen , Badalyan George , Harutyunyan Sergey , Gyulamiryan Ashot , Vartanyan Violetta , Petrosyan Silvia , Giordano Nicholas , Jacobs Todd , Wood Kent , Fritz Gilbert , Qadri Syed B. , Horwitz James , Wu Huey-Dau , Vechten Deborah Van , Gulian Armen
Published: June 2019

We have deposited and investigated thin films of lanthanum hexaborate with 1% of the lanthanum replaced by cerium. In bulk single-crystalline form, this material has, due to the Kondo-mechanism, the highest known Seebeck coefficient at sub-K temperatures. Thus it is a good candidate for several thermoelectric applications at very low temperatures. We are studying the kinetic properties of thin films such as the conductivity and Seebeck coefficient as a function of temperature and the dependence of these properties on film thickness, substrate material and deposition conditions. The consequent theoretical performance limits on the device applications of these films are considered with a focus on detectors and refrigerators.
Thermal Conductivity Of Bi/Sb Superlattice
Authors: Song D. W. , Chen G. , Cho S. , Kim Y. , Ketterson J. B.
Published: June 2019

The temperature-dependent cross-plane thermal conductivity of a 1-μm thick 50Å Bi / 50Å Sb superlattice on a (111) CdTe substrate was measured, using a differential 3-ω method. This method uses the temperature difference between the superlattice sample and a reference sample to calculate its cross-plane thermal conductivity. However, the substrate thermal conductivity is comparable to or smaller than the superlattice thermal conductivity near room temperature. This results in a very small or negative temperature difference, making the existing data reduction method inapplicable. Based on an improved model, the temperature-dependent thermal conductivity of the Bi/Sb superlattice is obtained and is about half of the literature value of Bi0.5Sb0.5 bulk alloy.
Avalanche Dynamics: Influence of the Granular Packing Size
Authors: Aguirre M. A. , Calvo A. , Ippolito I.
Published: June 2019

We present an experimental study about the stability and dynamics of a granular packing and the influence of the packing size on the avalanche mass and on its characteristic angles: maximum angle of stability and angle of repose.

For a system with a large enough number of granular layers only Nc superficial layers contribute to the avalanche mass. It can be observed that Nc strongly depends on the packing size. Experiments are done on monosize glass beads with packings of different sizes.
Signal Propagation in Nonlinear Granular Chain
Authors: Hong Jongbae
Published: June 2019

The vertical granular chain changes the elastic property of the medium due to gravity. Therefore, the solitary propagating mode in the horizontal chain disperses and damps in the vertical chain. We show that there are two different types of propagating modes, i.e., quasi-solitary and oscillatory, depending on the strength of impulse and the dispersion and damping of the signal follow power-laws. The power-law behavior in the linear oscillatory regime is explained analytically. The nonlinear solitary regime in which soliton damps and disperses due to gravity is discussed briefly.
Backscattering of Nonlinear Acoustic Impulses from Buried Inclusions in Granular Beds
Authors: Manciu Marian , Sen Surajit , Hurd Alan J.
Published: June 2019

Nonlinear acoustic impulses travel as weakly dispersive bundles of energy through 3-D, dry, granular assemblies. Such impulses can therefore be exploited to probe for buried objects in 3-D granular assemblies. In this article, we shall discuss the details of propagation of an impulse generated at the surface of a granular bed. The role of polydispersity will be briefly addressed. The calculations suggest that backscattered data, as received at predetermined locations at the surface, may be helpful in reconstructing an approximate image of the buried inclusion, as viewed from above.
Linear and Nonlinear Ultrasonic Properties of Granular Soils
Authors: Bonner Brian P. , Berge Patricia A. , Aracne-Ruddle Chantel M. , Bertete-Aguirre Hugo , Wildenschild Dorthe , Trombino Cosette N. , Hardy Edgar D.
Published: June 2019

The ultrasonic pulse transmission method (100-500 kHz) was adapted to measure compressional (P) and shear (S) wave velocities for synthetic soils fabricated from quartz-clay and quartz-peat mixtures. Velocities were determined as samples were loaded by small (up to 0.1 MPa) uniaxial stress to determine how stress at grain contacts affects wave amplitudes, velocities, and frequency content. Samples were fabricated from quartz sand mixed with either a swelling clay or peat (natural cellulose). P velocities in these dry synthetic soil samples were low, ranging from about 230 to 430 m/s for pure sand, about 91 to 420 m/s for sand-peat mixtures, and about 230 to 470 m/s for dry sand-clay mixtures. S velocities were about half of the P velocity in most cases, about 130 to 250 m/s for pure sand, about 75-220 m/s for sand-peat mixtures, and about 88-220 m/s for dry sand-clay mixtures. These experiments demonstrate that P and S velocities are sensitive to the amount and type of admixed second phase at low concentrations. We found that dramatic increases in all velocities occur with small uniaxial loads, indicating strong nonlinearity of the acoustic properties. Composition and grain packing contribute to the mechanical response at grain contacts and the nonlinear response at low stresses.
Unsteady Heat Conduction in Granular Materials
Authors: Vargas Watson L. , McCarthy Joseph J.
Published: June 2019

Heat transfer in granular materials impacts a variety of industrial applications, such as calcination, drying kilns, packed bed and multiphase reactors, etc. and may yield insight into the thermal response of some porous materials (in combustion synthesis or sintering, for example). In a dense bed of granular material, conduction occurs almost exclusively through the particle-particle contacts over a wide range of conditions. We have developed a novel Thermal Particle Dynamics (TPD) Simulation technique which incorporates both contact mechanics and contact conductance theories in order to model the dynamics of flow and heat conduction through granular materials. This model is uniquely suited to studying the effects of microstructure and flow on the dynamics of heat conduction in particulate materials. In this paper, we present experimental as well as numerical results of transient heat conduction through a bed of cylinders.
Liquid Filled Hourglasses: A Study of Interstitial Fluid Effects on the Kinetic Behavior of Granular Materials
Authors: Muite Benson K. , Hunt Melany L.
Published: June 2019

Experimental measurements of discharge rate and observations of flow pattern were made for spherical, monosized particles in a liquid- filled, hourglass shaped container. Different combinations of fluid properties, solid properties and vessel geometry exhibited a range of flow patterns that are described as lubricated, fluidized, oscillatory, or localized channeling discharges. A Bagnold number is used to present the discharge rate and flow regime results.
Erratum: Effect of Polydispersity on Stresses in Granular Shear Flow [Mat. Res. Soc. Symp. Proc. Vol. 627, BB4.6 (2000)]
Authors: Clelland Richard , Hrenya Christine M.
Published: June 2019

In Figure 2 of the aforementioned paper by Alam, Clelland, and Hrenya, the stresses obtained using molecular-dynamic simulations of binary-sized systems were compared to stresses obtained using the kinetic-theory model for binary mixtures developed by Willits and Arnarson (Phys. Fluids, 11, p. 3116, 1999). An error was found in calculations for the Willits and Arnarson theory. Figure 1 (below) shows the corrected theoretical predictions, along with the original simulation data. These corrections result in an improved match between simulations and theory. In particular, the theoretical predictions compare well with the simulation data across the entire range of diameter ratios investigated.
Size Segregation in Granular Beds Subject to Discrete and Continuous Vertical Oscillations
Authors: Fernando Dimuth N. , Wassgren Carl R.
Published: June 2019

Size segregation of particulates is of concern in a number of industries that handle materials such as chemicals, pharmaceuticals, fertilizers, and food products. Of particular interest in this paper is segregation resulting from externally applied vibration. In industrial applications this vibration may either be applied intentionally in devices such as vibrating conveyors or “live wall” hoppers, or unintentionally during material handling and transport. This paper investigates size segregation in granular beds subject to discrete “taps” and continuous, sinusoidal vertical vibration. The results from discrete element computer simulations indicate that the rise rate of a single impurity increases monotonically with amplitude for discrete vibrations but for continuous vibrations the rise rate increases, reaches a maximum value, then decreases as the oscillation amplitude increases.
Statistical Mechanics of Stress Transmission in Static Arrays of Rigid Grains
Authors: Grinev Dmitri V. , Edwards Sam F.
Published: June 2019

We develop the statistical-mechanical theory that delivers the fundamental equations of stress equilibrium for static arrays of rigid grains. The random geometry of static granular packing composed of rigid cohesionless particles can be visualised as a network of intergranular contacts. The contact network and external loading determine the network of intergranular forces. In general, the contact network can have an arbitrary coordination number varying within the system. It follows then that the network of intergranular forces is indeterminate i.e. the number of unknown forces is larger than the number of Newton's equations of mechanical equilibrium. Thus, in order for the network of intergranular forces to be determined, the number of equations must equal the number of unknowns. We argue that this determines the contact network with a certain fixed coordination number. The complete system of equations for the stress tensor is derived from the equations of intergranular force and torque balance, given the geometric specification of the packing. The granular material fabric gives rise to corrections to the Euler-Cauchy equation that become significant at mesoscopic lengthscales. The stress-geometry equation establishes the relation between various components of the stress tensor, and depends on the topology of the granular array.
Dislocation Multiplication in Germanium Single Crystals
Authors: Charbonnier Corinne , Kruml Tomas , Martin Jean-Luc
Published: June 2019

Thermal activation of <123> germanium single crystal deformation is studied by using stress-relaxation experiments. These exhibit a non logarithmic dependence of stress as a function of time. The athermal component of stress and the apparent activation volume are determined. The role of dislocation multiplication is discussed in terms of specific features of the monotonic and transient deformation behaviour.
Parallel Tight-Binding Simulations of Nanophase Ceramics: Atomic and Electronic Transport at Grain Boundaries
Authors: Tsuruta Kenji , Totsuji Hiroo , Totsuji Chieko
Published: June 2019

We report on tight-binding molecular dynamics (TBMD) of neck formation processes and atomistic and electronic diffusivity at grain boundaries of nanocrystalline silicon carbide. The TBMD simulations are based on an O(N) algorithm (the Fermi-operator expansion method) for calculating electronic contributions to energy and forces. The code has been fully parallelized on our PC-based parallel machines. The TBMD simulations of collision of SiC nanospheres show that the processes of neck formation depend strongly on contact angles between the two grains. Atomic diffusions are quite different in the necks formed with different angles. Also, the electronic transport property at grain boundary is investigated via a TB representation of an electronic diffusivity. A preliminary result on the diffusivity at a Σ=9 grain boundary of SiC indicates significant enhancement of electron mobility along the grain boundary.
Transition Regime Fracture Toughness-temperature Properties of two Advanced Ferriticmartensitic Steels
Authors: Spätig Philippe , Donahue Eric , Odette George R. , Lucas Glenn E. , Victoria Max
Published: June 2019

Advanced martensitic steels are leading candidate materials for fusion reactor structural components due to their resistance to void swelling, and good balance of physical and mechanical properties. However, irradiations at temperatures below about 400°C result in increases in the cleavage-to-microvoid coalescence transition temperature, as well as reductions in the upper-shelf tearing toughness. This paper reports on the transition regime fracture toughness properties of two unirradiated 7-9Cr martensitic alloys, F82H and T91. Effective fracture toughness-temperature curves, Ke(T), were measured in the transition regime using relatively small pre-cracked specimens. Three sets of data obtained on different specimen sizes and geometries for the two steels are analyzed. All the data can be placed on a single so-called master-curve, when shifts due to size/geometry and material are taken into account. The results from mechanical tests, finite element method (FEM) simulations of crack tip fields and confocal microscopy-fracture reconstruction observations are presented. The link between the different mechanisms taking place at various length scales, resulting in the complex process of cleavage fracture, is discussed.
Efficient silicon light emitting diodes made by dislocation engineering
Authors: Lourenço M. A. , Gwilliam R. M. , Shao G. , Homewood K.P.
Published: June 2019

Efficient room temperature silicon based light emitting diodes have been fabricated by conventional ULSI processes using a recently developed dislocation engineering approach. Strong silicon band edge luminescence was observed from devices fabricated by low energy boron implantation into silicon substrates followed by high temperature rapid thermal annealing. In this paper we review the luminescence properties of silicon light emitting diodes and give an example of how this approach can be employed to fabricate and optimise light emitting devices operating at different wavelengths.
Deep level study in epitaxial 4H-SiC grown on substrates inclined toward <1 100>
Authors: Kato Masashi , Ichimura Masaya , Arai Eisuke , Nishino Shigehiro
Published: June 2019

Epitaxial layers of 4H-SiC are grown on (0001) substrates inclined toward <1120> and <1100> directions. Defects in these films are characterized by deep level transient spectroscopy (DLTS) in order to clarify the dependence of concentrations and activation energies on substrate inclination. DLTS results show no such dependence on substrate inclination but show thickness dependence of the concentration.
Influence of substrate surface morphology on defect generation during silicon carbide single crystal growth
Authors: Um Myung Yoon , Jeong Jae Kyeong , Kim Bum Seok , Na Hoon Joo , Song In Bok , Kim Hyeong Joon
Published: June 2019

6H-SiC single crystals were grown on various substrates, treated mechanically and chemically in different conditions, by physical vapor transport. To investigate the defect evolution according to the different substrate treatment prior to the growth, the grown crystals were examined by optical micrograph, scanning electron microscopy, atomic force microscopy and molten KOH etching technique. The smoother substrate surface was, the lower defect density the grown SiC had. The highest quality SiC crystal was grown on substrate etched by hydrogen after polished by 0.25 νm diamond paste, having an edge/screw dislocation density of 7.3 ×102 / cm2 without micropipes. Defects, such as dislocations and micropipes, of the grown crystals are found to be strongly correlated with the substrate morphology.
Hydrogen Platelet Layer in Silicon Formed from Hydrogen Trapped onto Microbubbles of Gases
Authors: Usenko A.Y. , Carr W.N. , Chen Bo
Published: June 2019

Features of a process of delamination of crystalline silicon layer from silicon wafer along hydrogen platelet layer formed by microwave plasma hydrogenation are described. The process involves first making a buried layer of nuclei for hydrogen platelets. Ion implantation of inert or low-soluble gases is used to form the layer. The nuclei are microbubbles that appear along Rp plane of implanted ions. Results for argon, xenon, and krypton implantation are compared. Wafers thus processed with a dose of 1015cm-2 are then hydrogenated with a microwave plasma. During hydrogenation, an atomic hydrogen diffuses into the silicon wafer and collects onto internal surfaces of the microbubbles. Then the hydrogen increases the internal surface of the microbubbles by growing a platelet type extensions to the microbubbles. The extensions grow preferably along the buried layer plane. A silicon layer above the layer of grown platelets were delaminated through pre-bonding/cut/post-bonding sequence as in the Smart-cut process. The plasma hydrogenation of the trap layer may be used as a step in a process of fabricating of SOI wafers with a very thin top crystalline silicon layer. Also, implant doses needed to form the microbubble trap layer are much lower than doses of direct implantation of hydrogen in the Smart-cut process. Temperature range of 200°C to 400°C during the hydrogenation process allows effectively grow extended hydrogen platelets from the nuclei. Mechanisms of nucleation of platelets as extentions of microbubbles are suggested. Control of hydrogen outdiffusion/platelet growth with thermal trajectory during plasma processing is discussed.
Direct-Write Printing of Silver Metallizations on Silicon Solar Cells
Authors: Curtis C. J. , Rivkin T. , Miedaner A. , Alleman J. , Perkins J. , Smith L. , Ginley D. S.
Published: June 2019

Direct-write technologies offer the potential for low-cost materials-efficient deposition of contact metallizations for photovoltaics. We report on the inkjet printing of metal organic decomposition (MOD) inks with and without nanoparticle additions. Near-bulk conductivity of printed and sprayed metal films has been achieved for Ag and Ag nanocomposites. Good adhesion and ohmic contacts with a measured contact resistance of 400μΩ•cm2 have been observed between the sprayed silver films and a heavily doped n-type layer of Si. Silver deposited using the MOD ink burns through the Si3N4 antireflection coating when annealed at 850°C to form an ohmic contact to the n-Si underneath. An active solar cell device was fabricated using a top contact that was spray printed using the Ag MOD ink. Inkjet printed films show adhesion differences as a function of the process temperature and solvent. Silver lines with good adhesion and conductivity have been printed on glass with 100 μm resolution.
Study on the Dopedβ-FeSi 2 Obtained by Metal Vapor Vacuum Arc Ion Source Implantation and Post-Annealing
Authors: Wang Shuangbao , Liang Hong , Zhu Peiran
Published: June 2019

β-FeSi2 was firstly formed by implanting Si wafers with Fe ions at 50 kV to a dose of 5×1017/cm2in a strong current Metal Vapor Vacuum Arc (MEVVA) implanter. Secondly, Ti implantation was performed on these Fe as-implanted samples. The Fe + Ti implanted samples were furnace annealed in vacuum at temperatures ranging from 650 to 975°C. The XRD patterns of the annealed samples correspond to β-FeSi2 structure (namely β-Fe(Ti)Si2). When annealing was done above 1050°C, the β-Fe(Ti)Si2 transformed into α-Fe(Ti)Si2. This implies that introducing Ti stabilizes the β-FeSi2 phase. Resistance measurements were also performed.
TEM Studies and Contact Resistance of Au/Ni/Ti/Ta/n-GaN Ohmic Contacts
Authors: Zakharov D.N. , Liliental-Weber Z. , Motayed A. , Mohammad S.N.
Published: June 2019

Ohmic Ta/Ti/Ni/Au contacts to n-GaN have been studied using high resolution electron microscopy (HREM), energy dispersive X-ray spectrometry (EDX) and electron energy loss spectrometry (EELS). Two different samples were used: A - annealed at 7500C withcontact resistance 5×10-6 Ω cm2 and B-annealed at 7750C with contact resistance 6×10-5 Ω cm2. Both samples revealed extensive in- and out-diffusion between deposited layers with some consumption ofGaNlayerand formation of TixTa1-xN50 (0<x<25) at the GaN interface. Almost an order of magnitude difference in contact resistances can be attributed to structure and chemical bonding of Ti-O layers formed on the contact surfaces.
Optical and Structural Investigation of AlN Grown on Sapphire with Reactive MBE Using RF Nitrogen or Ammonia
Authors: Yun F. , He L. , Xiu F. , Morkoç H. , Bai S. , Shishkin Y. , Devaty R. P. , Choyke W. J.
Published: June 2019

AlN epitaxial layers in a thickness range of 0.065 to 0.6 microns have been grown on double-side polished c-plane sapphire by molecular beam epitaxy (MBE) using either RF nitrogen or ammonia as the nitrogen source. The samples were characterized by XRD, room temperature (RT) and low temperature (2K) optical absorption (transmission) measurements. The XRD (0002) peak FWHM diminishes from 380 arcsec to 84 arcsec when the thickness of the AlN films is increased from 65 nm towards 0.6 μm. All the samples grown with ammonia (NH3), representing N-rich conditions, exhibited optical bandgap exceeding 6 eV at RT. For samples grown with RF nitrogen source, we find that higher nitrogen flow (partial pressure of 8.3-9.4 × 10-5 Torr) results in optical bandgap values larger than 6.0 eV, regardless of the XRD results. The bandgap is found to be smaller than 6.0 eV for the samples grown with lower nitrogen partial pressure (1.0-3.5 x 10-5 Torr), regardless of sample thickness and the XRD data.
Transient Capacitance Characterization of Deep Levels in Undoped and Si-Doped GaN
Authors: Nakamura S. , Liu P. , Suhara M. , Okumura T.
Published: June 2019

The deep levels in both undoped and Si-doped GaN layer grown by metalorganic chemical vapor deposition have been characterized by photocapacitance and transient capacitance spectroscopy. The increase in the photocapacitance was observed in both GaN samples in the range of 1.8 to 2.2 eV. This is due to the photoionization of carriers from the deep levels associated with the yellow luminescence (YL). In addition, the transient capacitance measurements after the photoionization were also performed in the range of 1.8 to 3.4 eV. The notable transient of capacitance was observed at the photon energies of about 2.1 and 3.4 eV, the former could be associated with the change in the charge state of the YL center and latter might stem from some other defects capturing photogenerated carriers. By using the isothermal capacitance transient spectroscopy (ICTS) analysis, the ICTS peaks due to the deep levels associated with YL were detected at about t = 150 s in both GaN samples. In addition, another ICTS peak was detected only in the Si-doped GaN samples. It is considered that this peak is associated with the deep levels deeper than YL levels and the deeper levels originate from defects induced by Si doping.
Modeling of Thermal Conductivity of Polycrystalline GaN Films
Authors: Kotchetkov D. , Balandin A. A.
Published: June 2019

We present preliminary results of a theoretical investigation of the thermal conductivity of polycrystalline GaN films. It is assumed that grain boundaries play a major role in limiting the thermal conductivity, which is calculated using the phonon-hopping transport approach. The effect of the grain size, size dispersion, and inter-grain interface structure on the thermal conductivity values is analyzed. The obtained results are compared with available experimental data for polycrystalline films and model predictions for crystalline GaN films.
Thermal Boundary Resistance and Heat Diffusion in AlGaN/GaN HFETs
Authors: Filippov Konstantin A. , Balandin Alexander A.
Published: June 2019

We theoretically investigate the thermal boundary resistance and heat diffusion in AlGaN/GaN heterostructure field-effect transistors. Our calculations based on the diffuse mismatch model show that the thermal boundary resistance at the interface between GaN and SiC can strongly influence the temperature rise in the device channel.
GaP-based MIS Capacitors Using a SiN Gate Dielectric
Authors: Chen A. , Woodall J. , Wang X.W. , Ma T.P.
Published: June 2019

Gallium Phosphide (GaP) Metal-Insulator-Semiconductor (MIS) capacitors were fabricated with synthesized SiN as the gate dielectric. The interface property and the SiN bulk quality were studied with capacitance-voltage (C-V) measurements and current-voltage (I-V) measurements. The total interface state density of 3×1012 cm-2 and the fixed charge density in SiN of 7×1012cm-2 were estimated from the C-V measurements. The leakage current density was as low as 15nA/cm2 at an effective electric field of 3MV/cm. The effective electric field in SiN at breakdown was as high as 10MV/cm. Constant current stress measurements showed bulk trap density of 2×1011 cm-2 in SiN, which is much lower than that for CVD SiN or SiO2.
First AlGaN Free-Standing Wafers
Authors: Melnik Yu.V. , Soukhoveev V.A. , Tsvetkov K.V. , Dmitriev V.A.
Published: June 2019

Single crystal AlGaN bulk materials have been fabricated, for the first time. AlGaN thick (up to 0.6 mm) layers were grown by hydride vapor phase epitaxy on SiC substrates. The substrates were removed resulting in free-standing AlGaN wafers up to 0.5 inch in diameter. Fabricated AlGaN wafers were investigated by x-ray diffraction, transmission electron microscopy (TEM), and cathodoluminescence. X-ray diffraction and TEM studies confirmed single crystal structure of grown material. Based on x-ray diffraction results, AlN concentration in grown material was estimated of about 35 mol.%. Cathodoluminescence measurements demonstrated a number of peaks in UV spectral region with the most intense luminescence at a wavelength of about 325 nm (100 K). The wafers demonstrated n-type conductivity with electron concentration in the 1017 cm-3 range at room temperature. Development of AlGaN substrates with controlled alloy composition may lead to stress-free device epitaxial structures for AlGaN-based transistors and UV emitters and sensors.
Temperature Dependent Cathodoluminescence Characterization of Ultraviolet Emitting Films Grown by Pulsed Laser Deposition
Authors: Fitz-Gerald J.M. , Hoekstra J.G. , Bansal R.K. , Fowlkes J.D. , Rack P.D.
Published: June 2019

Strontium sulfide (SrS) is known to have an indirect bandgap of ∼ 4.32 eV. When doped with tellurium (Te), ultraviolet emission occurs at 360 nm (for Tes singlet) and 400nm (for Tes- Tes dimers) due to radiative recombination from bound exciton states. In this paper we discuss the ultraviolet emission of pulsed laser deposited thin films of SrS:Te grown as SrS-Te and SrSTe- SrS multi-layer structures on Si substrates. The Te doping was incorporated by conventional diffusion into the SrS films. Temperature dependent ultraviolet emission measurements were taken and will be discussed along with results from microstructural and chemical characterization techniques.
Laser Pointing Stability Measured by an Oblique-incidence Optical Transmittance Difference Technique
Authors: Gray J. , Thomas P. , Zhu X.D.
Published: June 2019

We describe an oblique incidence optical transmittance difference technique for determining the pointing stability of a laser. In this technique, we follow the angular drift a monochromatic laser beam by measuring the relative changes in transmittance through a parallel fused quartz window for s- and p- polarized components of the beam in response to the drift. This method is shown in the present experiment to have the sensitivity to detect angular changes in the range of 1.7 νradians. To demonstrate the technique we measured the angular drifts of two commercially available lasers.
Mechanical Properties and Morphology of Pulsed – Laser Deposited BaTiO3 Thin Films
Authors: Xu Jie , Durisin Daniel P. , Auner Gregory W.
Published: June 2019

BaTiO3 thin films have been grown on Si(100) substrate by KrF pulsed – laser deposition (PLD). The process parameters such as background gas pressure, substrate temperature, and laser fluence were varied in order to investigate their influence on the crystal structure, surface morphology and mechanical properties. The films were characterized by X-ray diffraction (XRD), UV/VIS/NIR spectrometer, atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS). The hardness, Young's modules and scratch testing of BaTiO3 films were measured using nano-indenter. The stoichiometric BaTiO3 films having uniform grains were grown. The defects and particulates were generated at higher laser fluence. The size and density of particulates were increased with tighter laser focus. The results from dynamic scratch test indicated that the films with good adhesion were grown at moderate laser fluence.
Inorganic-organic Hybrid Materials for Real 3-D Sub-νm Lithography
Authors: Houbertz R. , Schulz J. , Fröhlich L. , Domann G. , Popall M. , Serbin J. , Chichkov B.
Published: June 2019

Real 3-D sub-νm lithography was performed with two-photon polymerization (2PP) using inorganic-organic hybrid polymer (ORMOCER®) resins. The hybrid polymers were synthesized by hydrolysis/polycondensation reactions (modified sol-gel synthesis) which allows one to tailor their material properties towards the respective applications, i.e., dielectrics, optics or passivation. Due to their photosensitive organic functionalities, ORMOCER®s can be patterned by conventional photo-lithography as well as by femtosecond laser pulses at 780 nm. This results in polymerized (solid) structures where the non-polymerized parts can be removed by conventional developers.

ORMOCER® structures as small as 200 nm or even below were generated by 2PP of the resins using femtosecond laser pulses. It is demonstrated that ORMOCER®s have the potential to be used in components or devices built up by nm-scale structures such as, e.g., photonic crystals. Aspects of the materials in conjunction to the applied technology are discussed.
Biocompatibility Studies of the Nitinol Thin Films
Authors: Dinu C.Z. , Tanasa R. , Dinca V.C. , Barbalat A. , Grigoriu C. , Bucur E.O. , Dauscher A. , DeStefano V. Ferrari , Dinescu M.
Published: June 2019

Pulsed Laser Deposition method (PLD) was used to grow nitinol (NiTi) thin films with goal of investigating their biocompatibility. High purity Ni and Ti targets were alternatively ablated in vacuum with a laser beam (λ=355 nm, 10 Hz) and the material was collected on room temperature Ti substrates. X-ray diffraction, scanning electron microscopy, energy dispersive spectroscopy and atomic force microscopy analyses have been performed to investigate the chemical composition, crystalline structure and surface morphology of the NiTi films. The nitinol layers biocompatibility has been tested using as a metric the extent to whichthe cells adhereduring the culture period on the surface of NiTi layers deposited on Ti substrates. Vero and fibroblast cell lines dispersed into MEM (Eagle) solution containing 8% fetal bovine serum, at 37° C, were used for tests. Preliminary studies indicate that the interaction at the interface is specifically controlled by the surface morphology, (especially by surface roughness), and by the chemical state of the surface. Cell behavior after contact with NiTi/Ti structure for different intervals (18, 22 and 25 days for the Vero cells, and after 10 and 25 days for fibroblasts) supports the conclusion that NiTi is a very good candidate as a biocompatible material.
Mcc Corrosion Tests at Reference Testing Conditions for A27 Cast steel in Hanford Ground Water
Authors: Merz M.D. , Gerber F. , Wang R.
Published: June 2019

The Materials Characterization Center (MCC) at Pacific Northwest Lab- oratory is performing three kinds of corrosion tests for the Basalt Waste Isolation Project (BWIP) to establish the interlaboratory reproducibility and uncertainty of corrosion rates of container materials for high-level nuclear waste. The three types of corrosion tests were selected to address two distinct conditions that are expected in a repository constructed in basalt. An air/steam test is designed to address corrosion during the operational period and static pressure vessel and flowby tests are designed to address corrosion under conditions that bound the condi ring the post-closure period of the repository.

The results of tests at reference testing conditions, which were defined to facilitate interlaboratory comparison of data, are presented. Data are reported for the BWIP/MCC-105.5 Air/Steam Test, BWIP/MCC-105.1 Static Pressure Vessel, and BWIP/MC-105.4 Flowby Test. In those cases where data are available from a second laboratory, a statistical analysis of interlaboratory results is reported and expected confidence intervals for mean corrosion rates are given. Other statistical treatment of data include analyses of the effects of vessel-to-vessel variations, test capsule variations for the flowby test, and oven-to-oven variations for air/steam tests.
Statistics of Pit Initiation: Analysis of Current Transients During Passive Film Breakdown
Authors: Bertocci Ugo , Leigh S. , Orden A. C. Van , Yang G.
Published: June 2019

During the incubation period preceding pitting, current fluctuations indicate the beginning of the breakdown of the passive film. The charac- teristics of these current transients are being examined as a possible way to predict pitting. Stochastic models applied to the breakdown process have been proposed, and in order to test how well they account for the experi- mental results, various forms of processing of the current vs. time records are necessary. This paper describes the experimental data-taking methods, the processing routines so far developed for the statistical analysis of the data, and compares the experimental results with computer simulations based on a stochastic model.
The Theoretical Evaluation of Localised Corrosion in Radioactive Waste Canisters.
Authors: Sharland S.M.
Published: June 2019

Under repository conditions, it is likely that radioactive waste canisters will be subjected to both uniform and localised corrosion. Localised corrosion can take many forms depending on the precise physical and chemical environment of the metal at the time of attack, but generally the rates of penetration are much greater than those associated with uniform corrosion. The most likely forms under aerated repository conditions are pitting and crevice corrosion. To ensure adequate radionuclide containment an allowance for these rates must be included in the final canister dimensions. It is considered the best way to predict long term penetration rates is to develop mathematical models, which include all the physical and chemical processes necessary to describe the system and use experimentally determined input parameters relating to these processes. These models must then draw on further experimental data for validation over short timescales. In this paper, we discuss several techniques of modelling long term pit propagation in waste canisters. The complexity of the problem has lead to a number of physical and chemical approximations in the modelling. We investigate the applicability and ranges of validity of several of the more common approximations, both in our own models and in the literature, and compare the predictions with experimental pit growth rates. An investigatation of the sensitivity of the models to the various empirical input parameters indicates which need to be determined most accurately.
Solubility Modelling of Cements: Implications for Radioactive Waste Immobilisation.
Authors: Glasser F.P. , Macphee D.E. , Lachowski E.E.
Published: June 2019

The suitability of cement matrices for the long-term immobilisation of radionuclides cannot be predicted from short-term experimental data alone, because the chemical properties of cementitious systems change continuously over the repository lifetime. To model such changes is complex, so a stepwise approach has been adopted. A chemically simplified model for the solubility and compositional properties of calcium silicate hydrate gels in the system CaO-SiO2 -H20 was previously developed but has now been extended and improved and is applicable to gels in the wider composition range 0.8 < Ca/Si < 1.7. The effects of silicate speciation in aqueous solution on the formation of the solid phase have been more fully considered and the dissolution equilibrium has been revised. Solubility products and free energies of C-S-H formation have been evaluated and predictive applications of the model are discussed.
A Structured Programme of Research into the Chemical Aspects of Radioactive Waste Disposal
Authors: Read D. , Krol A.A. , Thompson B.G.J.
Published: June 2019

The UK Department of the Environment (DOE) is developing an independent capability to assess proposals made by the nuclear industry for the underground disposal of low and intermediate level radioactive waste. Modelling chemical processes forms an integral part of the underlying DOE research programme which includes the development of probabilistic risk assessment codes, more detailed deterministic models and supporting field and laboratory studies, in a co-ordinated, hierarchical approach. This paper summarises the results of a survey on the current status of this and related research, with emphasis on the assessment of a safety case for shallow land disposal of low level waste in about two years time. Shortcomings in existing work are identified, and a structured programme for future research described.