bluuebunny/crossref_metadata_2025_split huggingface dataset:
Crack Development in Pulsed Laser-Deposited Pzt Thin Films
Authors: Lee H. M. , Chuang T. J. , Chiang C. K. , Cook L. P. , Schenck P. K. 
Published: March 2011

ABSTRACTThe development of cracks in a PZT thin film prepared by pulsed laser deposition on an unheated Pt-coated silicon substrate, and subsequently crystallized by post-deposition annealing, was investigated as a function of film thickness. As deposited, the film was amorphous. The film was heated at 600°C to produce predominantly ferroelectric crystalline PZT. Spacing, width and morphology of cracks in the film followed a regular progression in which crack area decreased with decreasing film thickness. Data on area shrinkage, as deduced from crack area, were fit equally well as either a linear or a parabolic function of film thickness. It is suggested that crystallization-induced stresses rather than thermal-gradient related stresses, were dominant in the formation of the cracks, and that these stresses were modified by interaction with the substrate.
Laser Ablation of Pzt Films for use in Bimorph Actuator Structures
Authors: Frantti Johannes , Moilanen H. , Leppävuori S. , Uusimäki A. 
Published: March 2011

ABSTRACTLaser ablation has been used to produce piezoelectric films for use in a low voltage cantilever bimorph actuator structure. Nd doped lead zirconium titanate (PZT) films were deposited by a pulsed Q-switched Nd:YAG laser (wavelength 1064 nm) on to unheated silver-coated oxidised silicon substrates at a distance of 30 mm between substrate and target. Growth rates were typically 20 Å/s. The as-deposited PZT films were amorphous but contained small microcrystalline pyrochlore and perovskite regions. Optimisation of the annealing conditions resulted in perovskite as the main phase (T=750°C, t=2 h). A special fabrication technique (PbO covered PZT) was used to minimise film defects mainly caused by large particles.In order to improve the density of the film and deposition rates of the ablated PZT film, ablations using an XeCl excimer laser (wavelength 308 nm) under the influence of a static magnetic field were also studied. The decreased particle size in the deposited films showed that the surface quality of the films fabricated by the excimer laser was better than that of films deposited by the Nd:YAG laser. Films were studied using EDS, XRD and also micro-Raman spectrometry.Bimorph cantilever element structures were realised using Nd:YAG laser ablation. DC bending characteristics of these low voltage cantilever bimorphs were measured as a function of voltage using a Michelson interferometer. Displacements in the order of microns were obtained from a 15 mm x 4 mm x 80 �ement with a driving voltage level of 10 V.
Modulated Reflectance Spectroscopy of CdTe-Cd1−xMnxTe Multiple Quantum Wells and Superlattices Grown by Pulsed Laser Evaporation and Epitaxy
Authors: Labrie D. , Dubowski J.J. 
Published: March 2011

ABSTRACTPiezoreflectance and photoreflectance spectroscopies have been used to investigate the electronic properties of CdTe-Cd1-xMnxTe (x − 0.10) multiple quantum well and superlattice structures grown by Pulsed Laser Evaporation and Epitaxy (PLEE). The structures with the CdTe well widths from 54Å to 245Å have been investigated. The spectra exhibit a series of signatures which are attributed to free exciton transitions occuring between the heavy-hole and light-hole bands and the upper electron subbands within the CdTe well layers. The spectra indicate that the PLEE grown structures are of an excellent quality typical of the best currently available material.
Pulsed Laser Deposition of High Quality ZnO Thin Films
Authors: Amirhaghi S. , Craciun V. , Beech F. , Vickers M. , Tarling S. , Barnes P. , Boyd I. W. 
Published: March 2011

ABSTRACTThin films of ZnO have been grown on silicon and glass substrates by the pulsed laser deposition method. The effects of the oxygen partial pressure, substrate temperature and laser wavelength on the structural and optical properties of the films have been studied. The KrF excimer laser (at 248 nm) was found to produce better quality thin films than the frequency doubled Nd:YAG laser (532 nm). Layers produced at substrate temperatures as low as 300°C were c-axis oriented with a FWHM value for the 002 XRD reflection less than 0.2° and exhibited optical transmission higher than 80% in the visible region.
Microstructure and Properties of CoSi2 Thin Films on (100) Silicon by Laser Physical Vapor Deposition
Authors: Tiwari P. , Chowdhury R. , Narayan J. 
Published: March 2011

ABSTRACTLaser physical vapor deposition (LPVD) has been used to deposit thin CoSi2 films on (001)silicon at different substrate temperatures ranging from room temperature to 600°C. Particulate-free silicide thin films were characterized by X-ray diffraction, Rutherford backscattering, and high resolution transmission electron microscopy. We have found that films deposited at 200°C and below are amorphous; 400°C deposited films are polycrystalline whereas films deposited at 600°C are of epitaxial nature. The Effect of subsequent annealing on resistivity of room-temperature deposited thin films has been investigated. The resistivity value decreases to less than 15 μΩcm after annealing making these films suitable for microelectronics applications. The correlation between microstructure and properties of these films are discussed.
Ybco Encapsulation by Diamond Like Carbon Films Deposited by Laser Ablation Technique
Authors: Ganapathi L. , Giles S. , Rao Rama 
Published: March 2011

ABSTRACTWe have investigated the deposition and superconducting properties of YBCO thin films on single crystal LaAlO3, MgO and polycrystalline alumina substrates followed by the DLC (diamond like carbon) encapsulation [1]. DLC films were deposited at pressures ranging from high vacuum to 100 mT He. Substrate temperature was varied from 21°C to greater than 100°C. The process compatibility of Laser ablation technique for depositing both the materials was found convenient to sequentially depositYBCO and DLC films from high purity stoichiometric targets. Epitaxial YBCO films on (100) LaAlO3, (Tc−zero = 89K) and (100) MgO (Tc−zero = 85K) substrates showed identical superconducting transitions before and after encapsulation by a DLC layer. The encapsulated films showed no degradation due to acid treatment or aging over a period of 45 days. Similar results were obtained for YBCO films on polycrystallinealumina substrate. A buffer layer of YSZ was essential to obtain good superconductingproperties on alumina substrate. A 200 nm thick YSZ provided the barrier necessary for minimizing the interface reaction between Al2O3 and YBCO. Typically a Tce = 86 K was obtained for these films. These films were textured with c-axis perpendicular to the substrate surface. Likewise, there was no degradation of superconducting properties of these films after deposition of the DLC films or chemical attack by dilute HNO3.
Structure and Properties of a-C:N Films Prepared by Pulsed Excimer Laser Deposition
Authors: Xiong Fulin , Chang R. P. H. , White C. W. 
Published: March 2011

ABSTRACTWe present results on the synthesis of a-C:N films deposited by pulsed excimer laser ablation of graphite in a nitrogen gas ambient. Analysis with RBS and forward recoil spectrometry show that the films are hydrogen-free and nitrogen can be incorporated upto 40% by varying the nitrogen gas pressure. Electron microscopy has identified these films to be amorphous. Raman spectroscopy, infrared spectroscopy, and electron energy loss spectroscopy have revealed carbon-nitrogen bonding structures. Compared to a-diamond films prepared by the same technique, the C:N films still possess the properties of high mechanical hardness, chemically inertness and good wear resistance, but incorporation of nitrogen into the films generally degrades their diamond-like properties. The results suggest that nitrogen doping effect is resulted in the films under the present process, instead of carbon-nitrogen compound formation.
Polymerization of Isobutylene Initiated by Laser Vaporization of Metal Targets
Authors: Vann Walter , Daly George M. , El-shall M. Samy 
Published: March 2011

ABSTRACTA novel technique involving the initiation of polymerization using laser vaporization of metal targets is being explored. In the experiment, metal ions such as Ti+, Zr+, Ag+ are generated in the gas phase by pulsed laser vaporization/ionization of a metal target using the second harmonic of a Nd:YAG laser (532 nm). The ions are pulled toward a monomer liquid(isobutylene which can only be polymerized by cationic mechanisms) by applyingappropriate electric fields across the reaction chamber. Under different experimentalconditions (temperature, pressure of a carrier gas, laser energy, electric field strength, reaction time) different polymeric products (viscous liquids or solids) were obtained with average molecular weights ranging from 200 to greater than 106. Full characterization of these materials is currently in progress. This technique could lead to a powerful approach for the synthesis of a wide variety of polymeric materials with unique properties such as stability, strength and photo and electrical conductivity.
Strong Polarity and Bond Characterization of Nanostructured Silicon Nitride Solids
Authors: Zhang Lide , Mo Chimei , Wang Tao , Xie Cunyi 
Published: March 2011

ABSTRACTNanostructured silicon nitride solids (NANO–SSNS) were investigated by x–ray photoelectron spectroscopy (XPS), electron spin resonance (ESR) and dielectric measurements. It is found that the dielectric constant of NANO–SSNS depends strongly on the measuring frequency, f. When f<100Hz, at room temperature it is forty times as much as that of conventional Si3N4. ESR measurements show that a large number of unbinding electrons exist in interfaces. This suggests that the NANO–SSNS possess strong polarity. The study on the bond properties indicates that a large number of unsaturated and dangling bonds exist in interfaces of NANO–SSNS.
Synthesis of Transition Metal Clusters and Their Catalytic and Optical Properties
Authors: Wilcoxon J. P. , Martino A. , Baughmann R.L. , Klavetter E. , Sylwester A.P. 
Published: March 2011

ABSTRACTMetal Clusters may be synthesized in the interior of surfactant aggregates called inverse micelles. These nanosize chemical reactors permit the controlled growth of several types of metal clusters. We describe this process for the formation of Au, Ag, Pd, Pt and Ir clusters and cluster alloys. Two size-control strategies are described: 1)variation of micelle size by alteration of the surfacant and/or solvent combination used, and 2) judicious use of micelle interactions or phase behavior. Using these two methods size control in the range of 1-100 nm is possible. The optical properties of metal clusters of gold, silver, and gold/silver alloys are described and the surface plasmon resonances are shown to have dramatic blue shifts and extensive line broadening with decreasing size in the range of 10-1 nm. In the case of gold clusters, the distinct resonancein the visible disappears for sizes less than 2.0 nm and new features appear in the UV. The optical spectra of alloys of gold and silver are shown to differ dramatically from their homoatomic counterparts of the same average size. We use electron and X-ray diffraction to determine the phase structure of the metal clusters and small angle X-ray scattering, neutron scattering, light scattering and TEM to characterize the average size and size distributions of these clusters. Finally, we describe measurements of the catalytic activity of Pd clusters and demonstrate a dramatic increase in hydrogenation activity on the size range of 2-10 nm.
Nmr Study of Cluster-Assembled Nanophase Copper
Authors: Suits B. H. , Meng M. , Siegel R. W. , Liao Y. X. 
Published: March 2011

ABSTRACT63Cu and 65Cu NMR spectra from cluster-assembled nanophase copper with an average grain size between 5 and 10nm show a broadened peak, at the normal Knight-shifted frequency for copper metal, which arises from only the central 1/2 to -1/2 transition. A very broad background is observed on either side of that peak. Some samples exhibit a second broad peak at a position normally associated with non-metallic copper. Pulsed NMR measurements of the central peak show that virtually all the copper signals are significantly broadened and have a spin-spin relaxation time longer than larger grained copper samples. Line shape measurements, using spin echoes, as a function of delay between rf excitation and measurement show there are a number of copper sites with longer relaxation times which have a significantly larger broadening. Those sites are tentatively identified as being at or near a grain boundary or free surface. A small orientation effect is observed indicating an anisotropy within the samples. An isochronal anneal of one sample showed significant, but not complete, line narrowing after an anneal at 450°C consistent with other nanophase metals which show grain growth above 40-50% of the melting temperature.
Surface Structure - Catalytic Function in Nanophase Gold Catalysts
Authors: Sze Chien , Gulari Erdogan , Demczyk B.G. 
Published: March 2011

ABSTRACTCatalysts consisting of ultra-fine gold particles supported on iron oxide have been synthesized by the coprecipitation method. Subsequent to preparation, each sample was heat treated in air at four different temperatures, ranging from 473 K to 773 K. Steady state carbon monoxide oxidation was carried out over each sample. Upon extended reaction, catalyst deactivation took place over three of the catalysts whose respective surface compositions (e.g., gold to iron atomic ratio) were altered appreciably from their initial state. Surface structure analyses performed on all the unreacted catalysts have revealed variations in physical properties (e.g., degree of crystallinity and particle size). In addition, lattice parameters of gold were observed to increase up to 20 % from the bulk value. In contrast, XPS showed both gold and iron to be in essentially the same chemical states for all catalysts, irrespective of heat treatment temperatures. The importance of surface sensitive parameters to catalytic function are discussed.
Excess Thermodynamic Properties of Nanophase Titanium Dioxide Prepared by Chemical and Physical Methods
Authors: Terwilliger Chrysanthe D. , Chiang Yet-Ming 
Published: March 2011

ABSTRACTThe excess enthalpy and excess heat capacity of nanophase TiO2 prepared by a chemically-derived process and by inert gas condensation have been measured using differential scanning calorimetry. In comparison to the chemically-derived samples, the excess enthalpy of the inert gas condensed samples is significantly larger, perhaps due to the presence of intragranular planar defects that accomm oate oxygen deficiency. Significant extraneous contributions from planar defects, lattice strain, phase transformation, oxidation, or sintering have been ruled out for the chemically-derived samples. A grain boundary enthalpy of 13-1.6 J/m2 in the temperature range 600-1000°C is obtained from scanning measurements. However, the data also indicate a grain size and/or temperature dependence of the grain boundary enthalpy.
Effect of Porosity on Properties of Nanocrystalline Materials
Authors: El-Sherik A.M. , Erb U. , Krstic V. , Szpunar B. , Aus M.J. , Palumbo G. , Aust K.T. 
Published: March 2011

ABSTRACTThis paper discusses the effects residual porosity may have on some properties of nanocrystalline materials. The two examples considered here are Young's modulus and saturation magnetization. It will be shown that the large variations observed for these properties may be explained, at least in part, on the basis of the residual porosity in thematerials which may vary considerably depending on the production techniques used to synthesize nanostructured materials.
Structure of CoxAg100-x and Its Relation to GMR
Authors: Xiao John Q. , Samuel J. , Chien C. L. 
Published: March 2011

ABSTRACTWe have studied the structure of the Co-Ag granular system across the entire composition range, as well as the annealed samples, using transmission electron microscopy (TEM) and x-ray diffraction. GMR, as much as 80% at 5K and 25% at room temperature, have been observed. The absolute values of the resistivity (ρ) and the change of the resistivity (δρ) as functions of the magnetic Co concentration and the annealing temperature have been determined. A linear relation between δρ and I/rco, where rco is Co particle size, has been found. This result suggests that the magnetic scattering at the interfaces is crucial to GMR.
Crystallization Process of Fe73.5Cu1Nb3Si13.5B9
Authors: Nakabayasiii H. , Doi M. , Matsui M. , Doyama M. 
Published: March 2011

ABSTRACTTo clarify the relation between high magnetic permeability and magnetic phases of Fe73.5Cu1Nb3Si13.5B9 ribbons, the process of precipitation was investigated by using the Xray diffraction, DTA, VSM and the Mössbauer spectra at various annealing temperatures. The volume fraction of each magnetic phase was estimated. The sample annealed at 853K which shows maximum permeability is composed of partially ordered Fe3Si(70%), Fe(B) solid solution(10%) and amorphous(20%) phases. The relative permeability of the sample annealed below 853K increases with increasing the volume fraction of both of the Fe3Si partially ordered and the Fe(B) solid solution phases. The relationship between tile permeability and the volume fraction is interpreted by the random anisotropy model.
Nanophase Molecular Antiferromagnets
Authors: Papaefthymiou Georgia C. 
Published: March 2011

ABSTRACTNanometer-sized molecular complexes of superexchange-coupled iron ions with iron nuclearity n < 10 exhibit short-range intramolecular magnetic ordering and ‘particlelike’ superparamagnetism in their low temperature Mössbauer spectra. A comparative study of the magnetic properties of ca 10 Å diameter iron-oxo phases obtained through controlled hydrolytic polymerization of iron in non-aqueous solvents is presented. The magnetic anisotropy energy constant, K, which is proportional to the observed blocking temperature, TB, and the sharpness of the superparamagnetic transition depend critically on the iron oxidation state and degree of 3d-electron delocalization. Representative examples of mixed-valent iron complexes containing oxo-bridged, octahedrally coordinated iron with primarily either Fe(III) or Fe(II) character are discussed.
Real-Space Imaging of Nanoscale Electrodeposited Ceramic Superlattices in the Scanning Tunneling Microscope
Authors: Golden Teresa D. , Raffaelle Ryne P. , Phillips Richard J. , Switzer Jay A. 
Published: March 2011

ABSTRACTWe have imaged fractured cross-sections of electrodeposited ceramic oxides based on the TI-Pb-O system using a scanning tunneling microscope. The goal of this work is to measure both the modulation wavelength and compositional profile of the superlattices by mapping out the electronic properties in real space on a nanometer scale. Fourier analysis was done on STM images of all superlattices to yield the modulation wavelength. The modulation wavelength from STM was then compared with those obtained, by Faraday calculation and x-ray diffraction. The STM can be used to design “better” superlattices. We have found that the composition profile in superlattices deposited by modulating the potential was more square than in superlattices deposited by modulating the current.
Superhard Nanocomposite of Nitride Superlattices by Opposed-Cathode Unbalanced Magnetron Sputtering
Authors: Chu X. , Wong M. S. , Sproul W. D. , Barnett S. A. 
Published: March 2011

ABSTRACTNanocomposite films of polycrystalline nitride superlattices with nanometer grain size were deposited onto tool steel substrates by a one-step process using an opposed-cathode high-rate reactive unbalanced magnetron sputtering system. The superlattices are composed of alternating thin layers of different nitrides such as TiN/NbN and TiN/VN. The thicknesses of two neighboring layers were between 3 and 150 nm and were determined by the rotating speed of the substrate holder and the sputtering rate of the individual layer material. The films exhibited exceptional hardness as high as 5200 kgf/mm2 for TiN/NbN superlattice and 5 100 kgf/mm2 for TiN/VN superlattice. The hardnesses of the superlattice coatings were strongly dependent on several deposition parameters such as the superlattice period, the nitrogen partial pressure, and the substrate bias voltage. One of the possible mechanisms for the hardness enhancement is the effect of nanophase materials, which were created mainly by the influence of the artificially layered-structure and the low energy ion bombardment during film growth.
Synthetic Imogolite Paracrystals
Authors: Huling Jeffrey C. , Brinker C. Jeffrey , Ackerman William C. , Smith Douglas M. , Bailey Joseph K. , Farkas Janos 
Published: March 2011

ABSTRACTImogolite is a structurally microporous tubular clay comprising one-dimensional pore channels that are ∼1 nm in diameter. In addition to its novel tubular morphology, a notable structural characteristic of imogolite is its occurrence in paracrystalline tube bundles in which the individual tubes are close-packed with their axes in parallel alignment. We have developed a technique that aligns and tightly packs the tube bundles over macroscopic dimensions, in a manner analogous to the alignment and packing of the individual imogolite tubes within the bundles. This extends the range of imogolite paracrystallinity, effectively eliminating mesoporosity and nontubular phases.
New Nanocomposite Structural Ceramics
Authors: Niihara K. , Nakahira A. , Sekino T. 
Published: March 2011

ABSTRACTThe new materials design was established for the structural ceramics to break through the present monolithic and composite ceramics. In this concept, the ceramic-based composites were divided into two groups: micro and nanocomposite. The microcomposite is the so-called composite in which the micro-sized particles, whiskers, platelets and fibers are dispersed at the grain boundaries of matrix grains. The nanocomposites, on the other hand, have three types of structures: intra and intergranular nanocomposites and nano/nano composite. The intra and intergranular nanocomposites were found to show the tremendous improvement of mechanical properties even at elevated temperatures compared with those of monolithic and microcomposite ceramics. The nano/nano composites gave the new functions such as machinability and superplasticity like metals. Our final goal for developing supertough and strong ceramics was achieved by hybridizing the intra and intergranular nanocomposites with the micro-meter sized fibers. This new concept was found to be also applicable for ceramic-metal composite systems.
Characterizing The Microstructures Of TiN/TiB2 Nanocomposites With Energy Filtered Tem
Authors: Szabo V. , RÜhle M. , Su K. , Sneddon L.G. , Bonnell D. 
Published: March 2011

ABSTRACTRecent developments in boron chemistry have allowed the synthesis of TiN/TiB2 composites from polymeric precursors with grain sizes of the order of 10-500 nm. In order to optimize the properties through controlled processing, nucleation of the crystalline phases and subsequent microstructural evolution must be understood. However, the nitride and boride phases are difficult to distinguish in conventional TEM since the grains are too small for diffraction analysis and light elements are not detectable by energy dispersive X-ray spectroscopy.For the characterization a prototype of an energy filtering TEM (EFTEM) which utilizes an imaging electron energy loss spectrometer incorporated into the column of a normal TEM has been used for elastic filtering and electron spectroscopic imaging (ESI). The ESI-technique allows us to obtain two-dimensional maps of the elemental distribution. These techniques are applied to advantage in the microstructural analysis of the TiN/TB2 nanocomposites.