bluuebunny/crossref_metadata_2025_split huggingface dataset:
Heteroepitaxy and Waveguide Formation for Solution Deposited LiNbO3 Thin Layers
Authors: Clem P. G. , Payne D. A. 
Published: April 2011

AbstractLithium niobate thin layers have potential applications in integrated, high efficiency signal modulators, and in second harmonic generation devices. We report the solution deposition of heteroepitaxial LiNbO3 thin layers on (006), (110) and (012) sapphire. Factors affecting surface roughness were investigated by atomic force microscopy. The best results for optical losses occurred after fresh, 0.1M unhydrolyzed solutions were used. Channel waveguides were developed by lithography and proton exchange. Waveguides were formed in Nd3+- and Er3+-doped thin layers to confine light and assess the possibility of integrated waveguide lasers.
Plasma Synthesis of Rare Earth Doped Integrated Optical Waveguides
Authors: Raoux S. , Anders S. , Yu K. M. , Ivanov I. C. , Brown I. G. 
Published: April 2011

AbstractWe describe a novel means for the production of optically active planar waveguides. The technique makes use of a low energy plasma deposition. Cathodic-arc-produced metal plasmas are used for the metallic components of the films and gases are added to form compound films. Here we discuss the synthesis of A12-xErxO3 thin films. The erbium concentration (x) can vary from 0 to 100% and the thickness of the film can be from Angstroms to microns. In such material, at high active center concentration (x=l% to 20%), erbium ions give rise to room temperature 1.53μm emission which has minimum loss in silica-based optical fibers. With this technique, multilayer integrated planar waveguide structures can be grown, such as Al2O3/Al2-xErO3/A12O3/Si, for example.
Time-Dependent SHG in Thin Film Germanium-Doped Silica Waveguides
Authors: Dajani I. , Kester J. J. , Ranon P. M. , Brauer M. L. , Mcgillen D. J. 
Published: April 2011

AbstractThe evolution of second harmonic generation (SHG) in germanium doped silica planar waveguides is simulated numerically. Based on the asymmetric photoionization model, the total current in the waveguide is taken to be the sum of an asymmetric current and a current due to the resulting dc field. The interplay between these two currents causes the SHG to saturate in time. The saturation of SHG in length is due to diffraction.
New Nonlinear Optically Active Polymers Containing Hydrazone Chromophores
Authors: Mang M. N. , Bales S. E. , Brennan D. J. , Chartier M. A. , Gulotty R. J. , Haag A. P. , Inbasekaran M. N. , Langhoff C. A. , Newsham M. D. 
Published: April 2011

AbstractA family of new polymeric nonlinear optical materials with high second order non-linearities, good thermo-oxidative and reorientational stability, and low waveguide losses have been prepared from a series of chromophores containing hydrazone moieties. These new polymerizable chromophores can be readily prepared by the acid-catalyzed condensation of substituted arylhydrazines with functionalized ketones or aldehydes to give molecules that have μ3 values up to 2440 × 10−48 esu (1579 nm) in solution. Thermoplastic polycarbonates and poly(hydroxy ethers) containing hydrazone chromophores have been prepared with Tg's ranging from 135 °C to 285 °C. Epoxy systems crosslinked with amino-functional arylhydrazones, have high d33 values and high glass transition temperatures, albeit with lower relative thermo-oxidative stability. Simple Mach-Zehnder modulators and registered multi-level structures based on these polymers have been reported previously. One device, prepared from a hydrazone-containing poly(hydroxy ether), has an r33 value of 10 pm/V (1320 nm), and retains most of that activity to 140 °C.
Biocompatibility of Hylan Polymers in Various Tissue Compartments
Authors: Larsen N.E. , Leshchiner E. , Balazs E.A. , Belmonte C. 
Published: April 2011

AbstractHylans (hyaluronan derivatives) retain the biological compatibility of the natural hyaluronan and have enhanced rheological properties which expands their utility in medical applications. Hylan materials (hylan A fluid, hylan B gel) were evaluated in a variety of tissue compartments for local and systemic tissue reaction (gross and microscopic), residence time and overall behavior in vivo. Hylan material was implanted into the subcutaneous, intradermal, submucosal, intramuscular, eye (vitreus, anterior chamber, trabecular meshwork), and neural (sciatic nerve) tissues at volumes ranging from 0.50 ml/kg to 20 ml/kg (2.5 mg/kg to 100 mg/kg). There was no difference in tissue response to hylan implants at the various ‘doses’ evaluated; all samples tested were observed to be biocompatible and did not elicit significant tissue response. Therefore, tissue reaction of hylan implants was not dependent on dose or concentration of hylan administered, since implantation of small amounts resulted in the same response as implantation of large amounts of material. In one of the most sensitive tests of biocompatibility, hylan was found to have no adverse effect on nerve regeneration (severed sciatic nerves in rat), and the results indicated that hylan materials “regeneration-friendly” environment for peripheral nerve growth as commatpearriaelds tpor othveid BedS Sa controls.Hylan materials provide biologically and physically compatible intercellular matrices which are useful in a variety of medical applications, including use as viscosurgical and viscoprotective tools (to maintain space, separate and protect tissues) and as viscosupplementation devices and implants.
Engineered Bone from Polyglycolic Acid Polymer Scaffold and Periosteum
Authors: Kim Tae Ho , Jannetta Carol , Vacanti Joseph P. , Upton Joseph , Vacanti Charles A. 
Published: April 2011

AbstractThe ability to create bone from periosteum and biodegradable polymer may have significant utility in reconstructive orthopedic and plastic surgery. Polyglycolic acid (PGA) serves as a biodegradable matrix which can be configured to a desirable shape and structure. This study was conducted to generate new bone tissue from periosteum and PGA polymer and to compare the tissue to the bone tissue generated from periosteal cells seeded onto PGA polymer. Bovine periosteum, harvested from fresh calf limbs, was placed either directly onto PGA polymer (1 cm2) or onto tissue culture dishes for periosteal cell isolation. In Medium 199 media with antibiotics and ascorbic acid, the periosteum/PGA construct was cultured for one week, then implanted into the dorsal subcutaneous space of nude mice. Periosteal cells, cultured from pieces of periosteum for two weeks, were isolated into cell suspension and seeded (˜l-3× 107cells) onto PGA polymer (1 cm2); after one week in culture, the periosteal cell-seeded polymer was implanted into the subcutaneous space of athymic mice. Specimens, harvested at 4, 8, and 14 week intervals, were evaluated grossly and histologically. The periosteum/PGA constructs showed an organized cartilage matrix with early evidence of bone formation at 4 weeks, a mixture of bone and cartilage at 8 weeks, and a complete bone matrix at 14 weeks. Constructs created from periosteal cells seeded onto polymer showed presence of disorganized cartilage at 4 and 8 weeks, and a mixture of bone and cartilage at 14 weeks. Periosteum placed directly onto polymer will form an organized cartilage and bone matrix earlier than constructs formed from periosteal cell-seeded polymer. This data suggests that PGA is an effective scaffold for periosteal cell attachment and migration to produce bone which may offer new approaches to reconstructive surgery.
Growth and Doping of GaN Directly on 6H-SiC by MBE
Authors: Korakakis D. , Sampath A. , NG H.M. , Morales G. , Goepfert I.D. , Moustakas T.D. 
Published: April 2011

ABSTRACTWe report on methods for the growth of GaN by MBE directly on 6H-SiC substrates. The films were doped p-type by the incorporation of Mg and the samples were characterized by studying their structure and morphology by RHEED, XRD and SEM and their recombination properties by photoluminescence measurements. The undoped films were found to be atomically smooth with 2×2 surface reconstruction and have an x-ray rocking curve with a FWHM of 3.5 arcmin. The photoluminescence spectra indicate that recombination is dominated by transition across the gap. The p-type doped films have a rocking curve with FWHM of 6.5 arcmin. and the majority of recombination occurs through D-A transitions at 3.26 eV.
P-type Mg-doped GaN grown by molecular beam epitaxy using ammonia as the nitrogen source
Authors: Yang Z. , Li L.K. , Wang W.I. 
Published: April 2011

ABSTRACTThe electrical and luminescent properties of Mg-doped GaN films grown by molecular beam epitaxy (MBE) using ammonia as the nitrogen source have been investigated. Due to their different growth environments, the Mg-doped GaN films grown by MBE using ammonia exhibited properties that were different from similar films grown by metal-organic chemical vapor deposition (MOCVD). It has been found that the introduction of positive charges during growth is important in the achievement of p-type Mg-doped GaN grown by MBE using ammonia. With the introduction of a moderate nitrogen plasma, we have achieved p-type Mg-doped GaN films with a hole density of 4×1017 cm−3 and a mobility of 15 cm2/V-s at room temperature.
Conductivity Measurements on GaN Grown by OMVPE and HVPE
Authors: Ben-Chorin M. , Diener J. , Meyer B.K. , Drechsler M. , Volm D. , Amano H. , Akasaki I. , Detchprohm T. , Hiramatsu K. 
Published: April 2011

ABSTRACTWe report on conductance and cyclotron resonance (CR) experiments on GaN epitaxial films grown by the OMVPE and HVPE techniques. From a precise determination of the electron effective mass the donor binding energy in the effective mass approximation (EMT) is calculated. We obtain 31.7 meV. The transport experiments on the HVPE films show that the conductance is thermally activated with an activation energy of 15 meV in contrast to the OMVPE films which showed temperature independent conductivity for temperatures between 4 and 100 K.
Exciton Luminescence of Single-Crystal GaN
Authors: Müllhaüser J.R. , Brandt O. , Yang H. , Ploog K.H. 
Published: April 2011

ABSTRACTDetailed photoluminescence (PL) studies of high-quality MBE-grown single-crystal cubic and hexagonal GaN are presented. We identify free and bound exciton recombination. By means of a line-shape analysis, we quantitatively analyze our spectra, which were taken as a function of temperature (T = 4 - 300 K) and excitation density (Pex = 0.3 - 200W/cm2). We show the dominant recombination channel at 300 K to be free-excitonic in nature with an internal small-signal quantum efficiency of 6 · 10−3 for both cubic and hexagonal material. Based on a three-level model, activation energies for exciton dissociation are evaluated. Radiative (τrad ≈ 2 ns) and nonradiative lifetimes (τe ≈ 1μs, τh ≈ 20 ps) are determined, where in the latter case, electron and hole trapping are considered separately. Furthermore, we show that the dominant nonradiative recombination center, being a hole trap, saturates at Pex ≥ 20 W/cm2.
Room-Temperature Life Test of Nichia AlGaN/InGaN/GaN Blue Light Emitting Diodes
Authors: Osiński Marek , Helms Christopher J. , Berg Niel , Barton Daniel L. , Scott Phillips B. 
Published: April 2011

ABSTRACTWe report on the current status of room-temperature life testing of Nichia NLPB-500 blue light emitting diodes. So far, two tests have been completed. During the first 1000-h test, a constant current of 20 mA was maintained in all devices. During the second 1650 h test, groups of 3 or 4 devices were driven at currents ranging from 20 mA to 70 mA. Very little degradation has been observed in devices driven at normal conditions (20-30 mA), with a noticeable increase in degradation rate above 60 mA.
Directed Light Fabrication of Iron-Based Materials
Authors: Thoma D.J. , Charbon C. , Lewis G.K. , Nemec R.B. 
Published: April 2011

ABSTRACTDirected light fabrication (DLP) is a rapid fabrication process that fuses gas delivered metal powders within a focal zone of a laser beam to produce fully dense, near-net shape, 3-dimensional metal components from a computer generated solid model. This study used iron-based alloys to evaluate the microstructural development in the DLF process. Continuous microstructural features are evident, implying a continuous liquid/solid interface during processing. In addition, solidification cooling rates have been determined based upon secondary dendrite arm spacings in Fe-25wt.%Ni and 316 stainless steel. Cooling rates vary from 101-105 K s-1, and the solidification behavior has been simulated using macroscopic heat transfer analyses.
Synthesis of Magnetite Particles by Pulsed Alexandrite Laser Processing of Metallic Glass Precursors
Authors: Sorescu Monica , Schafer S.A. , Knobbe E.T. 
Published: April 2011

ABSTRACTSamples of Fe78B13Si9 and Fe81B13.5Si3.5C2 metallic glasses were irradiated with a pulsed alexandrite laser (λ=750 nm, τ=60 μs) using different laser fluences. Kinetics of laser-induced phase transformations and fluence dependence of magnetic properties were studied by scanning electron microscopy (SEM) and Mössbauer spectroscopy. Low laser fluences were found to induce changes in magnetic texture and onset of crystallization. High laser fluences, however, correlated with additional oxidation effects and the formation of stoichiometric Fe3O4 particles in the irradiated alloy system. An activation energy of 11.9 eV was estimated for the laser-driven synthesis of magnetite nanoparticles. Pulsed alexandrite laser processing is an intriguing alternative technique for the controlled synthesis of iron oxide phases from ferromagnetic glass precursors.
Melting Evaporation and Recrystallization of A-Sic:H Films by Excimer Laser
Authors: Wickramanayaka S. , Kitamura K. , Nakanishi Y. , Hatanaka Y. 
Published: April 2011

ABSTRACTA study of laser annealing of a-SiC:H films was carried out in order to obtain poly-SiC films. First, a-SiC:H films were fabricated at temperatures ranging from 30 to 400 °C. All these films show amorphous structure before the annealing process. After annealing by a single pulse of 248 nm laser, films show poly-SiC structure. The pulse energies used for these anneals varied from 30 to 300 mJ/pulse. After exposing to a laser pulse, the a-SiC:H films melt and recrystallize forming poly-SiC structure. In addition to this process, a fraction of the film is observed to be vaporized. This vaporized fraction depends on the original film composition, hardness and the laser pulse-energy. Electrical resistivity of the films before the annealing process lies in the region of 1015 Ωcm. This resistivity drops drastically after the annealing process.
Crystallization of Amorphous Titanium Oxide Thin Films by Pulsed UV-Laser Irradiation
Authors: Ichikawa Yo , Chi Hideaki Ada , Setsune Kentaro , Kawashima Syun-Ichiro , Kugimiya Koichi 
Published: April 2011

ABSTRACTEffects of ultraviolet (UV) laser irradiation on the local crystal structure have been investigated for amorphous Ti-O thin films sputtered on ST-cut quartz substrates. The irradiation was conducted with a pulsed KrF excimer laser of 248nm in wavelength. There were few changes in the optical transmission spectra of the films before and after the irradiation. The crystal structure of the films was characterized by electron diffraction, XPS and EXAFS analyses. The results obtained from these analyses suggest the films gradually crystallize to a TiO2 crystal with the rutile type structure by the increasing of the laser pulses.
Non-Equilibrium Two-Dimensional Model of Excimer-Laser Melting and Solidification of Thin Si Films on SiO2
Authors: Gupta Vikas V. , Song H. Jin , Im James S. 
Published: April 2011

ABSTRACTWe have developed a two-dimensional numerical model of excimer-laser melting and solidification that properly takes into account the non-equilibrium and transient nature of the process. The model incorporates a novel explicit finite difference scheme for efficiently solving the heat conduction equation and an algorithm that incorporates the interface response function for properly simulating the evolution of phase domains. The model provides space- and time-resolved information regarding the thermal profile and phase domains from which nearly all of the important solidification details can be extracted (e.g., interface location, solidification velocity, interfacial undercooling, etc.). For the simple partial-melting-and-vertical-regrowth scenario, results from the model converge with the results from the well-established one-dimensional model. As a result of its two-dimensional and non-equilibrium formulation, which also respects the amorphous and inert nature of the underlying oxide surface, the model is unique in its capability for properly simulating those solidification scenarios that involve extensive lateral growth of solids, as for example those behind the super-lateral growth phenomenon and various artificially controlled super-lateral growth processes.
Photo-Chemical Etching on Silicon-Carbide by Using Krf Excimer Laser and Xe2* Excimer Lamp
Authors: Hasegawa K. , Murahara M. 
Published: April 2011

ABSTRACTSilicon-carbide (SiC) has excellent refractivity in the range of soft X-ray and is well-used as a diffraction grating for Synchrotron-radiation (SR) light. This material has a high melting point, hardness and chemical stability. Therefore, etching of the material by chemical or physical methods is very difficult. We reported a photo-chemical etching method in which a SiC surface is placed in NF3 gas atmosphere and irradiated by the Xe2* excimer lamp light parallelly and the grating patterned KrF laser light of 248nm perpendicularly on the sample surface. The Xe2* excimer lamp light are employed for NF3 gas decomposition, and KrF laser light used for excitation on the sample surface. This photochemical etching reaction are detected by XPS, QMS and FTIR measurements. This method achieved 0.18 Å/shot in etching efficiency, and became maximum approximately 7 times as high as ArF laser light for photodecomposition.
Optical Detection of Slow Excited Neutrals in Plasma-Assisted Excimer Laser Ablation
Authors: Mukherjee P. , Sakthivel P. , Witanachchi S. 
Published: April 2011

ABSTRACTThe observation of a slow optically excited component in the excimer laser-ablated YBCO plume due to the presence of a biased ring electrode is reported. The temporal dynamics of the plume were investigated by using time-of-flight (TOF) optical emission spectroscopy (OES). Time-resolved emission signals reveal excitation and resultant fluorescence from slow-moving plume species in the presence of the discharge.
Time Resolved Vacuum Ultraviolet Observations of Excimer Laser-Produced Yba2cu3O7 Plasmas
Authors: Chrisey D.B. , Horwitz J.S. , Mehlman G. , Auyeung R.C.Y. , Dorsey P.C. 
Published: April 2011

ABSTRACTSimultaneous temporal and spatial resolution of the monochromatic vacuum ultraviolet emission from an excimer laser ablated YBa2Cu3O7 plasma has yielded quantitative information on the plasma generation and velocity. From the time resolved spectral data, plasma velocities were measured and found to be ∼2.3x106 cm/s. It was observed that vacuum ultraviolet emission from above the YBa2Cu3O7 surface does not occur until ˜20 ns after the beginning of the laser pulse. Energetic material continues to be ejected from the target for more than 100 ns after the end of the laser pulse.
Amorphous and Crystalline Phase Formation in Ni/Al Multilayer Thin Films
Authors: Lucadamo G. , Barmak K. , Michaelsen C. 
Published: April 2011

ABSTRACTWe have investigated reactive phase formation in magnetron sputter-deposited Ni/Al multilayer films with a 1:3 molar ratio and various periodicities ranging from 320 nm to a codeposited film with an effective periodicity of zero. The films were studied by x-ray diffraction, differential scanning calorimetry, electrical resistance measurements, and transmission electron microscopy. We find that a reaction which results in the formation of an amorphous phase has taken place during the multilayer deposition process. This reaction substantially reduces the driving force for subsequent reactions and explains why nucleation kinetics become important for these reactions. The mode of transformation for a film with 10 nm periodicity was investigated, in detail, by applying the Johnson-Mehl-Avrami analysis to data obtained from isothermal and constant heating rate differential scanning calorimetry, in combination with electron microscopy studies of the transformation microstructure.
Free Energy Calculations of Cu-Sn Interfaces
Authors: Ravelo R. , Baskes M. 
Published: April 2011

ABSTRACTExcess free energies of solid Cu - Solid Sn and Solid Cu - liquid Sn have been calculated employing an adiabatic switching formalism in a Molecular Dynamics (MD) framework. The atomic interactions are described by modified embedded atom method (MEAM) potentials which includes the angular dependence of the electron density to describe bond bending forces necessary to model covalent materials.
Crystallization of Amorphous Sputtered NiTi Shape-Memory Alloy Films
Authors: Gong F.F. , Shen H.M. , Wang Y.N. 
Published: April 2011

ABSTRACTThe crystallization of amorphous sputtered NiTi films was investigated for selected heat treatments. From x-ray diffraction patterns, when the films were annealed below the crystallization temperature, the intensity of the broad maximum centered at 2θ = 43.5° increased with increasing the annealing temperature and time. When the films were annealed at 550°C for 0.5hr, parent B2 phase and Ni4Ti3 precipitates appeared. For annealing temperature above 700°C, the films showed embrittlement and volatilization. Therefore the optimum heat treatment for the optimum shape memory effect is found. The average grain size increased slowly in the initial stage of annealing but remained almost unchanged when the films were annealed for more than 1hr. This is because the grain boundary grooving caused by the titanium at a certain temperature volatilization seriously hinder the grain growth.
An Ultrafast Thin-Film Microcalorimeter with Monola Yer Sensitivity (J/m2)
Authors: Lai S.L. , Infante P. , Ramanath G. , Allen L.H. 
Published: April 2011

ABSTRACTWe introduce a high-sensitivity (∼1 J/m2) scanning microcalorimeter that can be used to perform direct calorimetric measurements on thin film samples at ultrafast heating rate (∼104 °C/s). This novel microcalorimeter is fabricated by utilizing SiN thin-film membrane technology, resulting in dramatically reduced thermal mass of the system. Calorimetric measurements are accomplished by applying a dc-current pulse to the thin-film metal (Ni) heater which also serves as a thermometer, and monitoring the real-time voltage and current of the heater. The temperature of the system and the energy delivered to the system are then determined. This calorimetric technique has been demonstrated by measuring the melting process of thin Sn films with thickness ranging from 13 to 1000 Å, and shows potential for calorimetric probing of irreversible reactions at interfaces and surfaces, as well as transformations in nanostructured materials.