bluuebunny/crossref_metadata_2025_split huggingface dataset:
Intermolecular Vibrations in Fullerene Systems
Authors: Mitch M.G. , Lopinski G.P. , Lannin J.S. 
Published: April 2011

ABSTRACTIntermolecular vibrations in a variety of fullerene systems are reported that provide information on C60-C60 and alkali-metal - C60 interactions and disorder effects. Low frequency Raman scattering in laser polymerized C60 films are shown to exhibit additional modes not reported for bulk materials. This result is consistent with recent dimer calculations. Raman scattering and HREELS measurements are shown to provide complementary information on alkali-metal motions in K3C60. In FCC Na6C60 both octahedral site disorder effects and reduced Na-C bond lengths account for changes in the Raman spectrum relative to Na3C60.
Measurement of the Excited-State Molecular Polarizability of C60
Authors: Tang N. , Hellwarth R. W. , Partanen J. P. 
Published: April 2011

ABSTRACTWe use ∼30 ps pulses at 532 nm to measure the complex excited-state molecular polarizability αe in a C60/benzene solution. We determine the imaginary part of αe by measuring the excited-state absorption cross-section in a pump-probe experiment. In a degenerate-four-wave-mixing (DFWM) experiment, we find that in delayed probing of the complex index gratings formed by ∼30 ps pulses, the thermal and the excited-state polarizability changes both contribute to these transient gratings.
Analysis of a C60/Twelve Solvent Survey for Red Shifting of Spectra
Authors: Brandelik D. M. , Mclean D. G. , Sutherland R. L. 
Published: April 2011

ABSTRACTA survey of solvents with a wide variation of solubility for C60 and a broad variation in dielectric constant was investigated for possible red shifting of the linear absorbance spectra. Initial analysis shows that very small shifts are achieved. Molar extinction spectra were measured for C60 in each solvent in both the standard mode and with an integrating sphere. Comparison of the two methods has shown strong scattering effects. The UV-vis spectra revealed some broadening in the bands and in some cases supression of strong C60 bands. Fluorescence spectra also show broadening of bands and new fluorescence minima in some solvents indicating formation of complexes between the C60 and those solvents that contain nitrogen.
Thermodynamics of Co-Existing Phases at Phase Transitions in Fullerenes
Authors: Stepanov Eugene V. 
Published: April 2011

ABSTRACTA thermodynamic model describing the co-existence of phases at orientational phase transition in solid fullerenes is developed. It is shown that for such a transition in fullerene C60 characterized by the comparatively low enthalpy, heterophase fluctuations can lead to the wide temperature region of the phase co-existence within about 30 K below the 260 K transition point, and mainly determine the anomalies of thermodynamic characteristics observed within that region. By comparison of the theoretical dependence obtained on this basis with the experimental data on the x-ray diffraction and heat capacity measurements for C60, the energetical characteristics of the heterophase cluster formation are evaluated. The relative contribution of homophase and heterophase fluctuations to breaking the orientational order is discussed.
Effects of Catalyst Promoters on the Growth of Single-Layer Carbon Nanotubes
Authors: Kiang Ching-Hwa , Goddard William A. , Beyers Robert , Salem Jesse R. , Bethune Donald S. 
Published: April 2011

ABSTRACTThe discovery of a catalytic route to the growth of single-layer carbon nanotubes suggests that it may be possible to produce these materials with better selectivity and in higher yield. Increasing the production efficiency is essential for characterization and application of these materials. We have discovered several catalyst promoters, in particular S, Bi, and Pb, that greatly enhance the single-layer carbon nanotube yield, and extend the distribution of nanotube diameters to much larger sizes (> 3 nm). Co crystallites encapsulated in graphitic polyhedra also form abundantly when S, Bi, or W is present. Understanding these catalytic process is of substantial scientific and technological importance.
Nanobundles
Authors: Yase Kiyoshi , Tanigaki Nobutaka , Kyotani Mutsumasa , Yumura Motoo , Uchida Kunio , Ohshima Satoshi , Kuriki Yasunori , Ikazaki Fumikazu 
Published: April 2011

ABSTRACTFine molecular straw, carbon nanotube (NT) is aligned to form a bundle. The purified NTs are mixed with a plastic polymer (polypropylene: PP) and extruded from a small die with a diameter of 2 mm kept at 200°C. The threads of NT/PP blend are characterized by small angle X-ray diffractometry and transmission electron microscope to confirm the existence of nanobundle of NTs, which orient along the spinning direction.
Buckytube Cold Field Emitter Array Cathode Experiments
Authors: Fishbine B. H. , Miglionico C. J. , Hackett K. E. , Hendricks K. J. , Wang X. K. , Chang R. P. H. , Shovlin J. D. , Kordesch M. E. 
Published: April 2011

ABSTRACTWe discuss experiments and theory directed towards the development of a buckytube cold field emitter array electron cathode.
Nanotube Carbon Structure Tips - A Source of High Field Emission of Electrons
Authors: Chernozatonskii Leonid A. , Gulyaev Yu.V. , Kosakoyskaja Z.Ja. , Sinitsyn N.I. , Torgashov G.V. , Fedorov E.A. , Zakharchenko Yu.F. , Val'chuk V.P. 
Published: April 2011

ABSTRACTWe present the finding of experiments of considerable field emission from the films consisting of nanotube carbon structureson various substrates (Si, quartz, glass): density of emission current was up to 1-3 A/cm2 while electric field was about 100 V/μ. The “reconstruction” and “inversion” of field emission have also been observed after current breakdown.
Microstructures of Ultrathin Films of Sputtered PbTiO3
Authors: Wasa Kiyotaka , Satoh T. , Tab Ata K. , Adachi H. , Ichikawa Y. , Setsune K. 
Published: April 2011

ABSTRACTUltrathin films of perovskite PbTiO3, 10–100nm thick, were epitaxially grown on miscut (001)SrTiO3 substrate by rf-magnetron sputtering at 600°C. The electron microscope and high resolution x-ray diffraction analysis suggested the evidence of epitaxial growth of (001)PbTiO3/(001)SrTiO3 with three dimensional crystal orientation. The stoichiometric film shows extremely smooth surface with the surface roughness less than 3nm. Deposition on a miscut substrate under stoichiometric conditions is essential to make continuous thin films of single crystal perovskite PbTiO3.
A Study of Switching Behavior in Pb(Zr,Ti) O3 Thin Films Using X-Ray Diffraction
Authors: Eatough Michael O. , Dimos Duane , Tuttle Bruce A. , Warren William L. , Ramesh R. 
Published: April 2011

ABSTRACTPb(Zr,Ti)O3 (PZT) thin films are being developed for use in optical and electronic memory devices. To study ferroelectric switching behavior, we have produced relatively untextured PZT thin films on Si substrates. We have developed a method for using x-ray diffraction to observe domain switching in situ. Our study involved the use of a micro-diffractometer to monitor the switching behavior in relatively small (0.7mm diameter) electroded areas. Diffraction analyses were done while DC voltages were applied and removed, representing several places in the hysteresis loop. In particular, we were looking for relative intensity changes in the [h 00],[00l] diffraction peaks as a function of position in the hysteresis loop. Our study indicates that the 90° domain switching exhibited by bulk ferroelectrics, is very limited in films on Si when grain sizes are less than about 1 μm.
Energy Levels of Point Defects in Perovskite Oxides
Authors: Robertson J. , Warren W. L. 
Published: April 2011

ABSTRACTThe band structure and energy levels of defects in BaTi3, PbTiO3 and PbZrO3 are calculated and compared. The band gap of Pb(Zr,Ti)O3 varies little because the band edges are formed of Pb 6s and 6p states. The charged Ti and O vacancies are found to be shallow. Transition metal impurities at the B site are found to give rise to numerous charge states because of their high intra-atomic electron repulsion. The levels of Cr4+, Fe4+ and Co4+ lie near midgap. Ti3+ trapped electron centers become deep at higher Zr contents in PZT.
Vacancy Related Defects in Thin Film Pb(ZrTi)O3 Materials
Authors: Krishnan A. , Keeble D.J. , Ramesh R. , Warren W.L. , Tuttle B.A. , Pfeffer R.L. , Nielsen B. , Lynn K.G. 
Published: April 2011

ABSTRACTPositron annihilation techniques have been applied to characterize vacancy-related defects in ferroelectric thin film structures. Variable energy positron beam measurements were carried out on doped and undoped Pb(Zr,Ti)O3 (PZT) samples subjected to different post-deposition cool down and anneal conditions. The PZT was deposited by sol-gel with either with platinum or RuO2 electrodes, or by laser ablation with La0.5Sr0.5CoO3 electrodes. The RuO2 and La0.5Sr0.5CoO3 electrode samples showed a smaller S-parameter compared to those deposited with Pt electrodes consistent with an improved PZT layer quality. For laser ablated samples cooled in a reducing ambient an increase in S-parameter for both the PZT and La0.5Sr0.5CoO3 layers was observed indicating an increase in neutral or negatively charged open-volume defects.
Spectroscopic Ellipsometry Characterization of La2Ti2O7 Thin Films
Authors: Dickerson Bryan D. , Nagata Masaya , Song Y.J. , Nam H.D. , Desu Seshu B. 
Published: April 2011

ABSTRACTOptical properties of La2Ti2O7 thin films were investigated by spectroscopie ellipsometry and compared to those of bulk sintered ceramics. Thin films were prepared by pulsed laser deposition (PLD) from bulk targets. To separate the effects of thickness, porosity, and index of refraction on observed Ψ and δspectra in thin films, a Cauchy model for n vs. λ was developed from sintered samples, with known porosity. Assuming the effective bulk index of refraction followed the rule of mixtures, corrected models for La2Ti2O7 without porosity were used to determine thickness and porosity of thin films as a function of fabrication parameters such as laser energy, substrate material and temperature. Ellipsometry models were tested and refined through XRD, EDX, ESCA, and SEM.
Study on Multilayered Electrodes for Ferroelectric Thin Film Capacitors
Authors: Chung Ilsub , Lee J.K. , Lee Wan In , Chung C.W. 
Published: April 2011

ABSTRACTThe ferroelectric properties of PZT on RuO2 electrodes were compared to those on RuOStudy on Multilayered Electrodes for Ferroelectric Thin Film Capacitors. It seems that the microstructure of PZT film plays an important role in the improvement of electrical properties. In particular, the change in the grain size of PZT film is responsible for the enhancement of the electrical properties. It was found in this study that films with smaller grain size had larger coercive fields. The exact dependence of the grain size on the hysteretic property is not fully understood at present. However, it is believed that the grain size affects both domain formation and domain pinning because of the influence of grain boundaries. The change in physical properties of PZT films due to the bottom electrode is understood in terms of interfacial modifications. Here we report on a method to modify physical properties of PZT films utilizing interfacial engineering.
Pt Hillock Formation and Decay
Authors: Summerfelt Scott R. , Kotecki Dave , Kingon Angus , Al-Shareef H.N. 
Published: April 2011

ABSTRACTThe formation of Pt hillocks during high temperature processing is a problem when using Pt as a bottom electrode for high dielectric constant materials. The hillock height is frequently larger than the dielectric thickness, degrading the leakage current of the device. In this work, Pt was deposited by electron beam evaporation on in-situ formed 40 nm ZrO2 coated SiO2 / Si substrates. The samples were then annealed at temperatures between 400°C and 700°C for times ranging from 2 min to 40 min. The surface roughness was measured by atomic force microscopy (AFM). The surface was characterized using Ra, RMS and Zmax over 5 μm × 5μm regions. Zmax is sensitive to hillock formation and Ra is sensitive to changes in general surface roughness. Analysis of Zmax indicates that 100 nm Pt / ZrO2 deposited at 315°C forms hillocks above 450°C during initial heatup. Subsequently, the hillocks decay for temperatures of 600°C and above such that they are almost gone after a 30 min air anneal. In-situ wafer stress measurements of Pt / ZrO2 were performed in O2 at temperatures up to 650°C. The Pt relaxes above 500°C in O2.
Liquid Delivery CVD of Ferroelectric (Pb,La)(Zr,Ti)O3 Thin Films
Authors: Tao W. , Desu S.B. , Peng C.H. , Dickerson B. , Li T.K. , Thio C.L. , Lee J.J. , Hendricks W. 
Published: April 2011

ABSTRACTHigh quality lanthanum doped PZT films were deposited on platinum coated silicon wafers by direct liquid injection MOCVD using lead bis-tetramethylheptadione, lanthanum tri-tetramethylheptadione, zirconium tetramethylheptadione, and titanium ethoxide as precursors. The films were deposited at 650°C and a reduced pressure of 5 Torr. The deposition rates were higher than 10 nm/min. The liquid delivery system led to highly reproducible deposition rate, composition, and ferroelectric properties in the PLZT films. The remanent polarization of the films decreased from about 25 μC/cm2 for PLZT(0/55/45) to about 12 μC/cm2 for PLZT(8/55/45). The coercive field of the films seemed to be independent on the La doping concentration up to 8% La doping.
Growth of Epitaxial BaTiO3 Thin Films at 600°C by Metalorganic Chemical Vapor Deposition
Authors: Kaiser D.L. , Vaudin M.D. , Rotter L.D. , Wang Z.L. , Cline J.P. , Hwang C.S. , Marinenko R.B. , Gillen J.G. 
Published: April 2011

ABSTRACTMetalorganic chemical vapor deposition (MOCVD) was used to deposit epitaxial BaTiO3 thin films on (100) MgO substrates at 600°C. The metalorganic precursors employed in the deposition experiments were hydrated Ba(thd)2 (thd = C11H19O2) and titanium isopropoxide. The films were analyzed by means of transmittance spectroscopy, wavelength dispersive x-ray spectrometry, secondary ion mass spectrometry depth profiling, x-ray diffraction, high resolution transmission electron microscopy, selected area electron diffraction, nanoscale energy dispersive x-ray spectrometry and second harmonic generation measurements. There was no evidence for interdiffusion between the film and substrate. The x-ray and electron diffraction studies showed that the films were oriented with the a-axis normal to the substrate surface, whereas second harmonic generation measurements showed that the films had some c-axis character.
Influence of the Sol-Gel Synthesis Conditions on the Properties of Thin PbTiO3Films
Authors: Retuert P.J. , Velilla T.P. , Martin V. Del C. , Avila R.E. 
Published: April 2011

ABSTRACTTetragonal, perovskite type, powders and thin films of PbTiO3have been synthesized by the sol-gel method, using trihydrate lead acetate and titanium tetraisopropoxide as starting alkoxides. The thermal treatment has been established from differential thermal and thermogravimetric analysis. An interpretation is presented for the various processes occurring during the gel to dense oxide conversion. The optimal process towards thin films includes annealing stages at 180, 400 and 650°C. Thin films were prepared by spinning on Si and Pt-covered Si. By SEM analysis the films appear cracked, porous, or homogeneous, with 0.5 to 1 um per solution coating. Current-voltage characteristics of Al/PT/Pt/Si capacitors exhibit a resistivity of 0.5 to 20·108Ωm, nondestructive breakdown in the range of 4 to over 20V, and relative dielectric permittivity of 100.
Preparation and Electrical Characteristics of (100), (111), and Randomly Oriented PZT Thin Films
Authors: Kim Chang Jung , Yoon Dae Sung , Lee Joon Sung , Choi Chaun Gi , Lee Won Jong , No Kwangsoo 
Published: April 2011

ABSTRACTThe (100), (111) and randomly oriented PZT thin films were fabricated on Pt/Ti/Coming 7059 glass using sol-gel method. The thin films having different orientation were fabricated by different drying conditions for pyrolysis. The preferred orientations of the PZT thin films were observed using XRD, rocking curves, and pole figures. The microstructures were investigated using SEM. The hysteresis loops and capacitance-voltage characteristics of the films were investigated using a standardized ferroelectric test system. The dielectric constant and current-voltage characteristics of the films were investigated using an impedance analyzer and pA meter, respectively. The films oriented in a particular direction showed superior electrical characteristics to the randomly oriented films.
In Situ Monitoring in the Pulsed Laser Deposition of Ferroelectric Thin Films
Authors: Schenck Peter K. , Vaudin Mark D. , Lee Byeong W. , Bonnell David W. , Hastie John W. , Paul Albert J. 
Published: April 2011

ABSTRACTOptical multichannel emission spectroscopie studies and ICCD (intensified charge coupled device) imaging have been applied to real-time, in situ gas phase species identification and plume structure analysis during the pulsed excimer laser deposition (PLD) of various ferroelectric thin films. Additional information on the non-excited plume species has been obtained using molecular beam-sampling mass spectrometry. The materials studied included targets of PbZr0.53Ti0.47O3 (PZT) and BaTiO3. For the BaTiO3 films, the partial pressure of oxygen in the buffer gas and the atomic oxygen emission within the plume both correlated with the observed lattice parameter, as determined by X-ray analysis. Reduced plume oxygen content resulted in an increased lattice parameter that, in turn, could be related to a reduced oxygen content in the film. ICCD imaging of plumes from PZT targets identified the presence of ejected particulates in the plume after multiple laser shots had worked the target surface. Scanning electron microscopy (SEM) studies of the PZT target surface and film morphology, revealed cone-like formations on the target and éjecta on the films which correlated well with the ICCD observation of plume particulates.
Y-Ba-Cu-O/PZT Current Controllable Distributed RC-Element
Authors: Hagberg J. , Levoska J. , Leppävuori S. , Murtoniemi T. 
Published: April 2011

ABSTRACTA superconducting, current controllable, distributed RC-component was designed and fabricated. The component consisted of YBa2Cu3O7 (YBCO) thin film resistor, which was covered with a dielectric layer and an electrode to form a capacitor. The YBCO thin film was deposited by pulsed laser ablation on a SiTiO3 (100) substrate. It was patterned by photolithography and wet etched to form a tapered strip. This YBCO strip was covered with a lead zirconate titanate layer made by laser ablation and, finally, the dielectric layer was covered with a gold electrode by vacuum evaporation. The electrical characteristics of the superconducting YBCO film and the -element were measured.Using the constructed component, high-pass and notch filter circuits were demonstrated. It was possible to control the electrical properties of these filters by a dc-current applied through the YBCO strip which causes the superconducting film to be come partly resistive.
Pile-Up Based Hall-Petch Considerations at Ultra-Fine Grain Sizes
Authors: Smith T. R. , Armstrong R. W. , Hazzledinew P. M. , Masumura R. A. , Pande C. S. 
Published: April 2011

AbstractThe dislocation pile-up explanation for the Hall-Petch (H-P) relation is re-examined for ultrafine grain sizes when only a few dislocations are involved in the pile-up, formed necessarily at applied stress levels near to the theoretical limit. Each dislocation added to the pile-up produces a step reduction in the H-P stress. Consequently, differences in dislocation configurations and types of pile-ups are easily recognized in the limit of small dislocation numbers. A significant reduction occurs in the H-P slope value (i.e., microstructural stress intensity) for the extreme case of only one dislocation loop being expanded against the grain boundary obstacle stress.
Spatio-Temporal Evolution of Dislocation Patterns in Fatigued Metals: Fundamental Limitations Imposed by Grain Size
Authors: Glazov Michael V. , Laird Campbell 
Published: April 2011

AbstractAn attempt to employ the self-organization theory has been made in order to describe different types of dislocation patterning in fatigued metals. We demonstrate that the formation of certain patterns can be understood as a result of competition between the intrinsic length scales of the “reaction+diffusion” model, on the one hand, and grain size, L on the other hand. Our results indicate that a critical grain size, Lcr, exists such that below Lcr the formation of dislocation structures of any type in fatigued metals becomes impossible.
Producing and Controlling Substrate Temperature Uniformity from 600°C to 1100°C in CVC Rotating Disk Reactors
Authors: Gurary A. I. , Tompa G. S. , Stall R. A. , Kroll W. J. , Zawadzki P. , Schumaker N. E. 
Published: April 2011

AbstractRotating Disk Reactors used for Chemical Vapor Deposition have evolved into a leading manufacturing technology for several materials, including metals, compound semiconductors, oxides, silicides, and nitrides. One of the hurdles to be surmounted in bringing this technology into routine high yield manufacturing has been to produce and maintain a highly uniform temperature distribution over the deposition area. With our recent introduction of the real-time Rotating Wafer Thermal Imaging (RWTI) technique, we have made dramatic improvements in the implementation of multi-zone heating systems and producing a uniform deposition temperature. Using multi-zone heaters we have demonstrated wafer temperature uniformity of less than 2°C in the temperature range from 600°C to 1100°C for 50 mm substrates located on wafer carriers with diameters from 125 to 300 mm. The wafer temperature uniformity dependence upon process parameters such as reactor pressure, reactant flows, and wafer carrier rotation speed was investigated. We have shown that multi-zone heating systems can provide high wafer temperature uniformity over a wide range of the process parameters, whereas single zone heating can provide a high degree of wafer temperature uniformity only for a limited set of process parameters. The experimental data allowed us to establish requirements for the application of single and multi-zone heating systems in vertical MOCVD Rotating Disk Reactors.
The Modeling Routes for the Chemical Vapor Deposition Process
Authors: Pons M. , Bernard C. , Rouch H. , Madar R. 
Published: April 2011

AbstractThe purpose of this article is to present the modeling routes for the chemical vapor deposition process with a special emphasis to mass transport models with near local thermochemical equilibrium imposed in the gas-phase and at the deposition surface. The theoretical problems arising from the linking of the two selected approaches, thermodynamics and mass transport, are shown and a solution procedure is proposed. As an illustration, selected results of thermodynamic and mass transport analysis and of the coupled approach showed that, for the deposition of Si1-x Gex solid solution at 1300 K (system Si-Ge-Cl-H-Ar), the thermodynamic heterogeneous stability of the reactive gases and the thermal diffusion led to the germanium depletion of the deposit.